# April 2011, Volume 20, Number 1

**M. A. Ibrahim, S. Minaei, E. Yuce**
[references] [full-text]

All-Pass Sections with High Gain Opportunity

In this paper, two new circuits for realizing firstorder voltage-mode (VM) all-pass section (APS) with variable gain are presented. The first proposed filter uses a single differential difference current conveyor (DDCC), one grounded capacitor and three resistors. The second proposed filter consists of two DDCCs, three grounded resistors and one grounded capacitor. It provides highinput and low-output impedances and can provide high gain. Both of the proposed circuits do not require any element matching condition. Moreover, oscillator circuits with minimum number of active and passive elements are derived from the proposed APSs. The proposed circuits are tested experimentally or by simulation using SPICE program to confirm the theory.

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Keywords: All-pass section, DDCC, voltage-mode, oscillator

**N. Herencsar, J. Koton, J. Jerabek, K. Vrba, O. Cicekoglu**
[references] [full-text]

Voltage-Mode All-Pass Filters Using Universal Voltage Conveyor and MOSFET-Based Electronic Resistors

The paper presents two novel realizations of voltage-mode first-order all-pass filters. Both circuits use single universal voltage conveyor (UVC), single capacitor, and two grounded resistors. Using the two NMOS transistors-based realizations of the electronic resistor with two symmetrical power supplies, presented all-pass filter circuits can be easily made electronically tunable. Proposed filter structures provide both inverting and non-inverting outputs at the same configuration simultaneously and they have high-input and low-output impedances that are desired for easy cascading in voltage-mode operations. The nonidealities of the proposed circuits are also analyzed and compared. The theoretical results of both circuits are verified by SPICE simulations using TSMC 0.35 μm CMOS process parameters. Based on the evaluation, the behavior of one of the circuits featuring better performance was also experimentally measured using the UVC-N1C 0520 integrated circuit.

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- IBRAHIM, M. A., KUNTMAN, H., CICEKOGLU, O. First-order all-pass filter canonical in the number of resistors and capacitors employing a single DDCC. Circuits, Systems, and Signal Processing, 2003, vol. 22, no. 5, p. 525 - 536.
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- MAHESHWARI, S. A canonical voltage-controlled VM-APS with a grounded capacitor. Circuits, Systems, and Signal Processing, 2008, vol. 27, no. 1, p. 123 - 132.
- METIN, B., PAL, K., CICEKOGLU, O. All-pass filters using DDCC- and MOSFET-based electronic resistor. International Journal of Circuit Theory and Applications, accepted in 2010 and available online, DOI: 10.1002/cta.682.
- CHEN, H. P., LIN, M. T., YANG, W. S. Novel first-order noninverting and inverting output of all-pass filter at the same configuration using ICCII. IEICE Trans. Electronics, 2006, vol. E89-C, no. 6, p. 865 - 867.
- HERENCSAR, N., KOTON, J., VRBA, K. A new electronically tunable voltage-mode active-C phase shifter using UVC and OTA. IEICE Electronics Express, 2009, vol. 6, no. 17, p. 1212 - 1218.
- HERENCSAR, N., KOTON, J., VRBA, K., CICEKOGLU, O. Highinput and low-output impedance voltage-mode all-pass filter using single universal voltage conveyor. In Proceedings of the 33th Int. Conf. on Telecommunications and Signal Processing - TSP’10. Baden near Vienna (Austria), 2010, p. 42 - 46.
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Keywords: All-pass filter, analog signal processing, MOSFET-C circuit, universal voltage conveyor, voltage-mode

**J. Koton, N. Herencsar, K. Vrba**
[references] [full-text]

Current and Voltage Conveyors in Current- and Voltage-Mode Precision Full-Wave Rectifiers

In this paper new versatile precision full-wave rectifiers using current and/or voltage conveyors as active elements and two diodes are presented. The performance of these circuit solutions is analysed and compared to the opamp based precision rectifier. To analyze the behavior of the functional blocks, the frequency dependent RMS error and DC transient value are evaluated for different values of input voltage amplitudes. Furthermore, experimental results are given that show the feasibilities of the conveyor based rectifiers superior to the corresponding operational amplifier based topology.

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Keywords: Precision full-wave rectifier, current conveyor, voltage conveyor, instrumentation, measurements

**A. Kubankova, D. Kubanek**
[references] [full-text]

Extended Method of Digital Modulation Recognition and Its Testing

The paper describes a new method for the classification of digital modulations. ASK, 2FSK, 4FSK, MSK, BPSK, QPSK, 8PSK and 16QAM were chosen for recognition as best known digital modulations used in modern communication technologies. The maximum value of the spectral power density of the normalized-centered instantaneous amplitude of the received signal is used to discriminate between frequency modulations (2FSK, 4FSK and MSK) on one hand and amplitude and phase modulations (ASK, BPSK, QPSK, 8PSK and 16QAM) on the other hand. Then the 2FSK, 4FSK and MSK modulations are classified by means of spectrums. The histograms of the instantaneous phase are used to discriminate between ASK, BPSK, QPSK, 8PSK and 16QAM. The method designed was tested with simulated and measured signals corrupted by white Gaussian noise.

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Keywords: Modulation recognition, modulation classification, spectrum, instantaneous phase, modulation features

**O. Aydemir, T. Kayikcioglu**
[references] [full-text]

Wavelet Transform Based Classification of Invasive Brain Computer Interface Data

The input signals of brain computer interfaces may be either electroencephalogram recorded from scalp or electrocorticogram recorded with subdural electrodes. It is very important that the classifiers have the ability for discriminating signals which are recorded in different sessions to make brain computer interfaces practical in use. This paper proposes a method for classifying motor imagery electrocorticogram signals recorded in different sessions. Extracted feature vectors based on wavelet transform were classified by using k-nearest neighbor, support vector machine and linear discriminant analysis algorithms. The proposed method was successfully applied to Data Set I of BCI competition 2005, and achieved a classification accuracy of 94 % on the test data. The performance of the proposed method was confirmed in terms of sensitivity, specificity and Kappa and compared with that of other studies used the same data set. This paper is an extended version of our work that won the Best Paper Award at the 33rd International Conference on Telecommunications and Signal Processing.

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Keywords: Brain computer interface, classification, electrocorticogram, pattern recognition, wavelet transform.

**R. Burget, J. Karasek, Z. Smekal**
[references] [full-text]

Recognition of Emotions in Czech Newspaper Headlines

With the growth of internet community, many different text-based documents are produced. Emotion detection and classification in text becomes very important in human-machine interaction or in human-to-human internet communication with this growth. This article refers to this issue in Czech texts. Headlines were extracted from Czech newspapers and Fear, Joy, Anger, Disgust, Sadness, and Surprise emotions are detected. In this work, several algorithms for learning were assessed and compared according to their accuracy of emotion detection and classification of news headlines. The best results were achieved using the SVM (Support Vector Machine) method with a linear kernel, where the presence of the dominant emotion or emotions was analyzed. For individual emotions the following results were obtained: Anger was detected in 87.3 %, Disgust 95.01%, Fear 81.32 %, Joy 71.6 %, Sadness 75.4 %, and Surprise 71.09 %.

- COWIE, R., DOUGLAS-COWIE, E., SAVVIDOU, S., MCMAHON, E., SAWEY, M., SCHRODER, M. Feel trace: An instrument for recording perceived emotion in real time. In Proceedings of the ISCA Workshop on Speech and Emotion. Newcastle (Northern Ireland, UK), 2000.
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Keywords: Emotion corpus, Emotion detection, Emotion classification, Text mining, Czech language

**B. Epple, H. Henniger, S. Kurz, H. Haan**
[references] [full-text]

Rural Optical-Propagation Measurements

Compared with traditional communication technologies like wired or radio frequency communications, optical wireless communication has a unique fading behavior of the received signal, that does not allow to use existing channel models without modification. In this paper the statistics of received optical power obtained from experimental data are compared to often used statistical mathematical models. These models are the log-normal and the gamma-gamma distribution. It was found that the gamma-gamma gives better fits to the measured data, but the quality of the log-normal fits is sufficient for most needs. This means that the log-normal distribution can be used for the development of simplified channel models which have a better mathematical tractability than the models based on the gamma-gamma distribution.

- ANDREWS, L. C., PHILLIPS, R. L. Laser Beam Propagation through Random Media, Second Edition. SPIE Press Monograph vol. PM152, 2005.
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- ANDREWS, L. C. Field Guide to Atmospheric Optics. Bellingham (USA): SPIE Press, 2004.

Keywords: Optical wireless, communications, measurement, channel model, free-space, FSO, OWC

**O. Pribula, M. Janosek, J. Fischer**
[references] [full-text]

Optical Position Sensor Based on Digital Image Processing: Magnetic Field Mapping Improvement

Optical position measurement system for an automated magnetic field mapping apparatus based on fluxgate sensors is presented. For the exact position estimation of the sensor head, a simple smart camera was developed with respect to minimal hardware configuration and real-time execution of position measurement algorithm. The camera is observing the mapped scene and evaluates position of the sensor head using an active marker. The sensor head is designed as movable, what allows keeping the scene fixed and exactly referenced to the mapped magnetic field using coordinates obtained from image. With image sensor fixed 2.5 m above the plane and range ±130 mm around the lens optical axis (image center), the total position measurement error is less than 0.5 mm.

- TUMANSKI, S., LISZKA, A. The methods and devices for scanning of magnetic fields. Journal of Magnetic Materials, 2002, vol. 242-245, Part 2, p. 1253-1256.
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- El GAMAL, A., ELTOUKHY, H. CMOS image sensors. IEEE Circuits and Devices Magazine, May-June 2005, vol. 21, no. 3, p. 6- 20, doi:10.1109/MCD.2005.1438751
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Keywords: Position measurement, magnetic field mapping, smart camera

**Usama S. Mohammed, Mostafa Salah**
[references] [full-text]

Tag Anti-collision Algorithm for RFID Systems with Minimum Overhead Information in the Identification Process

This paper describes a new tree based anti-collision algorithm for Radio Frequency Identification (RFID) systems. The proposed technique is based on fast parallel binary splitting (FPBS) technique. It follows a new identification path through the binary tree. The main advantage of the proposed protocol is the simple dialog between the reader and tags. It needs only one bit tag response followed by one bit reader reply (one-to-one bit dialog). The one bit reader response represents the collision report (0: collision; 1: no collision) of the tags' one bit message. The tag achieves self transmission control by dynamically updating its relative replying order due to the received collision report. The proposed algorithm minimizes the overhead transmitted bits per one tag identification. In the collision state, tags do modify their next replying order in the next bit level. Performed computer simulations have shown that the collision recovery scheme is very fast and simple even with the successive reading process. Moreover, the proposed algorithm outperforms most of the recent techniques in most cases.

- BONUCCELLI, M. A., LONETTI, F., MARTELLI, F. Tree slotted aloha: a new protocol for tag identification in RFID networks. In Proc. of IEEE Int. Symposium on a World of Wireless, Mobile and Multimedia Networks, 2006, p. 603-608.
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- JI H. CHOI, DONGWOOK LEE, HYUCKJAE LEE Query Tree- Based Reservation for Efficient RFID Tag Anti-Collision. IEEE Communications Letters, Jan. 2007, vol. 11, no. 1, p. 85-87.
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- SHIYU LI, QUANYUAN FENG A novel anti-collision algorithm in RFID system. In Electromagnetics Research Symposium. Cambridge, USA, 2008, p. 207-210.
- CHEN-CHUNG LIU, YIN-TSUNG CHAN An anti-collision protocol of RFID based on divide and conquer algorithm. In The 26th Workshop on Combinatorial Mathematics and Computation Theory, 2009.
- ZIMING GUO, BINJIE HU A dynamic bit arbitration anticollision algorithm for RFID system. In IEEE International Workshop on Anti-Counterfeiting, Security, Identification. 2007, p. 457 – 460.
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- SUNG HYUN KIM, POOGYEON PARK An efficient tree-based tag anti-collision protocol for RFID Systems. IEEE Communications Letters, 2007, vol. 11, no. 5, p. 449-451.
- JIHOON MYUNG, WONJUN LEE, JAIDEEP SRIVASTAVA Adaptive binary splitting for efficient RFID tag anti-collision. Communications Letters, IEEE, Mar 2006, vol. 10, no. 3, p.144- 146.
- JIHOON MYUNG, WONJUN LEE, JAIDEEP SRIVASTAVA, SHIH, T. K. Tag-splitting: adaptive collision arbitration protocols for RFID tag identification. IEEE Transactions on Parallel and Distributed Systems, 2007, vol. 18, no. 6, p. 763 – 775.
- WEI-CHIH CHEN, SHI-JINN HORNG, PINGZHI FAN An enhanced anti-collision algorithm in RFID based on counter and stack. In Proceedings of the Second International Conference on Systems and Networks Communications (ICSNC 2007), Issue 25- 31, 2007.
- YUAN-HSIN CHEN, SHI-JINN HORNG, RAY-SHINE RUN, JUI-LIN LAI, RONG-JIAN CHEN, WEI-CHIH CHEN, YI PAN, TERANO TAKAO A novel anti-collision algorithm in RFID systems for identifying passive tags. IEEE Transaction on Industrial Informatica, Feb. 2010, vol. 6, no. 1.
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Keywords: Passive RFID tag, anti-collision protocol, binary tree protocol, Aloha-based protocols.

**M. V. N. Rao, K. R. Rajeswari**
[references] [full-text]

Design of Discrete Frequency Coded Sequences using PSOCM for Target Detection with CAF

This paper presents the design of Discrete Frequency Coded (DFC) sequences with good auto correlation properties using Particle Swarm Optimization with Cauchy Mutation (PSOCM) technique. The crossambiguity function method is used to detect the stationary and moving targets in various target detection scenarios. The contour plots of the cross-ambiguity function are computed as a function of delay and Doppler frequency shift. The results are compared with DFC sequences of the sequence lengths N = 32 and N = 100.

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Keywords: Discrete Frequency Coded Sequences, Cross Ambiguity Function, Particle Swarm Optimisation.

**J. Rajnoha, P. Pollak**
[references] [full-text]

ASR Systems in Noisy Environment: Analysis and Solutions for Increasing Noise Robustness

This paper deals with the analysis of Automatic Speech Recognition (ASR) suitable for usage within noisy environment and suggests optimum configuration under various noisy conditions. The behavior of standard parameterization techniques was analyzed from the viewpoint of robustness against background noise. It was done for Melfrequency cepstral coefficients (MFCC), Perceptual linear predictive (PLP) coefficients, and their modified forms combining main blocks of PLP and MFCC. The second part is devoted to the analysis and contribution of modified techniques containing frequency-domain noise suppression and voice activity detection. The above-mentioned techniques were tested with signals in real noisy environment within Czech digit recognition task and AURORA databases. Finally, the contribution of special VAD selective training and MLLR adaptation of acoustic models were studied for various signal features.

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Keywords: Robust speech recognition, robust ASR, front-end, parameterization, feature extraction, noisy speech, spectral subtraction, voice activity detection

**K. Bartusek, J. Prinosil, Z. Smekal**
[references] [full-text]

Optimization of Wavelet-Based De-noising in MRI

In the paper, a method for MR image enhancement using the wavelet analysis is described. The wavelet analysis is concentrated on the influence of threshold level and mother wavelet choices on the resultant MR image. The influence is expressed by the measurement and mutual comparison of three MT image parameters: signal to noise ratio, image contrast, and linear slope edge approximation. Unlike most standard methods working exclusively with the MR image magnitude, in our case both the MR image magnitude and the MR image phase were used in the enhancement process. Some recommendations are mentioned in conclusion, such as how to use a combination of mother wavelets with threshold levels for various types of MR images.

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Keywords: Wavelet transformation, filtering technique, magnetic resonance imaging

**M. Simka, M. Drutarovsky, V. Fischer**
[references] [full-text]

Testing of PLL-based True Random Number Generator in Changing Working Conditions

Security of cryptographic systems depends significantly on security of secret keys. Unpredictability of the keys is achieved by their generation by True Random Number Generators (TRNGs). In the paper we analyze behavior of the Phase-Locked Loop (PLL) based TRNG in changing working environment. The frequency of signals synthesized by PLL may be naturally influenced by chip temperature. We show what impact the temperature has on the quality of generated random sequence of the PLL-based TRNG. Thank to analysis of internal signals of the generator we are able to prove dependencies between the PLL parameters, statistical parameters of the generated sequence and temperature. Considering the measured results of experiments we form a new requirement in order to improve the robustness of the designed TRNG.

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Keywords: TRNG, phase-locked loop, cryptographic attacks, tracking jitter, on-line randomness tests, FIPS 140-2

**Z. Xia, L. Yang, X. Sun, W. Liang, D. Sun, Z. Ruan**
[references] [full-text]

A Learning-Based Steganalytic Method against LSB Matching Steganography

This paper considers the detection of spatial domain least significant bit (LSB) matching steganography in gray images. Natural images hold some inherent properties, such as histogram, dependence between neighboring pixels, and dependence among pixels that are not adjacent to each other. These properties are likely to be disturbed by LSB matching. Firstly, histogram will become smoother after LSB matching. Secondly, the two kinds of dependence will be weakened by the message embedding. Accordingly, three features, which are respectively based on image histogram, neighborhood degree histogram and run-length histogram, are extracted at first. Then, support vector machine is utilized to learn and discriminate the difference of features between cover and stego images. Experimental results prove that the proposed method possesses reliable detection ability and outperforms the two previous state-of-the-art methods. Further more, the conclusions are drawn by analyzing the individual performance of three features and their fused feature.

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Keywords: Communication security, steganalysis, histogram gradient energy, neighborhood degree histogram, run-length histogram, support vector machine

**J. Svihlik, K. Fliegel, P. Koten, S. Vitek, P. Pata**
[references] [full-text]

Noise Analysis of MAIA System and Possible Noise Suppression

This paper is devoted to the noise analysis and noise suppression in a system for double station observation of the meteors now known as MAIA (Meteor Automatic Imager and Analyzer). The noise analysis is based on acquisition of testing video sequences in different light conditions and their further statistical evaluation. The main goal is to find a suitable noise model and subsequently determine if the noise is signal dependent or not. Noise and image model in the wavelet domain should be based on Gaussian mixture model (GMM) or Generalized Laplacian Model (GLM) and the model parameters should be estimated by moment method. Furthermore, noise should be modeled by GMM or GLM also in the space domain. GMM and GLM allow to model various types of probability density functions. Finally the advanced denoising algorithm using Bayesian estimator is applied and its performance is verified.

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Keywords: MAIA, meteor, noise analysis, GMM, GLM, Bayesian estimator, dicrete wavelet transform

**W. Liang, X. Sun, Z. Xia, D. Sun, J. Long**
[references] [full-text]

A Chaotic IP Watermarking in Physical Layout Level Based on FPGA

A new chaotic map based IP (Intellectual Property) watermarking scheme at physical design level is presented. An encrypted watermark is embedded into the physical layout of a circuit by configuring LUT (Lookup Table) as specific functions when it is placed and routed onto the FPGA (Field-Programmable Gate Array). The main contribution is the use of multiple chaotic maps in the processes of watermark design and embedding, which efficiently improves the security of watermark. A hashed chaotic sequence is used to scramble the watermark. Secondly, two pseudo-random sequences are generated by using chaotic maps. One is used to determine unused LUT locations, and the other divides the watermark into groups. The watermark identifies original owner and is difficult to detect. This scheme was tested on a Xilinx Virtex XCV600-6bg432 FPGA. The experimental results show that our method has low impact on functionality, short path delay and high robustness in comparison with other methods.

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Keywords: IP reuse technology, FPGA, chaotic map, LUT, IP watermarking

**V. Ricny, M. Slanina**
[references] [full-text]

Analysis of Resolution in Aerial Earth Surface Photography

The paper deals with a simplified analysis of subjective resolution of an aerial sensing system for Earth surface photography in the visible light spectrum. The proposed simplified linear method allows approximate estimation of the minimal target size in the image scanned using a camera with CCD sensor.

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Keywords: Aerial photography, resolution, target size, modulation transfer function, CCD sensor.

**V. Novotny**
[references] [full-text]

Optimization of Hierarchical System for Data Acquisition

Television broadcasting over IP networks (IPTV) is one of a number of network applications that are except of media distribution also interested in data acquisition from group of information resources of variable size. IP-TV uses Real-time Transport Protocol (RTP) protocol for media streaming and RTP Control Protocol (RTCP) protocol for session quality feedback. Other applications, for example sensor networks, have data acquisition as the main task. Current solutions have mostly problem with scalability - how to collect and process information from large amount of end nodes quickly and effectively? The article deals with optimization of hierarchical system of data acquisition. Problem is mathematically described, delay minima are searched and results are proved by simulations.

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Keywords: Data acquisition, multicast, SSM, multimedia, RTP/ RTCP, sensor networks

**P. Lafata, P. Jares**
[references] [full-text]

Analysis of Simulation Methods for Far-end Crosstalk Cancellation

The information capacity of current digital subscriber lines is limited mainly by a crosstalk in metallic cables. The influence of near-end crosstalk (NEXT) can be well cancelled by frequency duplex method, but the elimination of far-end crosstalk (FEXT) is not so easy. Therefore FEXT is the dominant source of disturbance in current digital subscriber lines (xDSL). One of the most promising solutions for far-end crosstalk cancellation is Vectored Discrete Multi-tone modulation (VDMT). For the testing of VDMT modulation efficiency it will be necessary to implement advanced methods for modeling of far-end crosstalk to obtain required predictions of the crosstalk behavior in a cable. The actual simple FEXT model is not very accurate and does not provide realistic results. That is why the new method for modeling of far-end crosstalk was developed and is presented in this paper. This advanced model is based on the capacitive and inductive unbalances between pairs in a cable and it also respects the cable’s internal structure. The results of the model are subsequently used for the simulation of VDMT modulation and its impact on the FEXT cancellation. These simulations are based on the estimations of transmission speed of VDSL2 lines with VDMT modulation.

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Keywords: Digital subscriber line, crosstalk, FEXT, VDMT modulation, VDSL2

**A. Aggelis, E. T. Sarris, V. Katos**
[references] [full-text]

A Location Privacy Extension for DVB-RCS

In this paper we studied the DVB-RCS (Return Channel through Satellite) standard from a privacy perspective and proposed an approach to incorporate a location privacy enhancing mechanism into the standard. Offering location based privacy in DVB-RCS communication is a challenge as the location of a satellite terminal must be revealed to the network operator of the DVB-RCS network for technical and administrative reasons. We proposed an approach of cloaking the location by intentionally compromising its accuracy whilst maintaining the operability and integrity of the communications system. In addition we implemented a proof of concept technique utilizing the theoretical findings of this work on a real DVB-RCS system, presenting the methodology along with the tools used and the experimental results.

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Keywords: DVB-RCS security, location privacy, satellite communications, data cloaking, spatial accuracy

**S. M. S. Sadough**
[references] [full-text]

Improved Reception Schemes for Digital Video Broadcasting Based on Hierarchical Modulation

In this paper, we first provide an overview of Hierarchical Modulation (HM) along with the opportunities offered by this modulation in the context of the recent Digital Video Broadcasting standard for Satellite to Handheld devices (DVB-SH).With HM, the binary data is partitioned into a “high-priority” (HP) and a “low-priority” (LP) bit stream that are separately and independently encoded before being mapped on non-uniformly spaced constellation points. We will show that the robustness of the HP stream is obtained at the expense of performance degradation of the less protected LP stream with respect to a non-hierarchical modulation. To overcome this inherent drawback of HM, we propose two different reception schemes for improving the bit error rate performance of the less protected LP stream, while keeping the HP decoding performance unchanged. The important point is that in one of the proposed reception schemes, the performance improvement is achieved together with the reduction of the receiver’s complexity.

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Keywords: DVB-SH standard, non-uniform hierarchical modulation, turbo code, concatenated coding, improved iterative decoding

**T. Vanek, M. Rohlik**
[references] [full-text]

Analysis of Broadcast Authentication Mechanism in Selected Network Topologies

This paper deals with simulation of the broadcast authentication protocols using Colored Petri Nets and further optimizations in Matlab environment. Typical application of broadcast authentication protocols can be configurations where only one transmitter with multiple recipients exists (such as message exchange in sensor networks routing protocols, or the leader election process in sensors network). Authentication of every packet seems to be very effective way to mitigate an attack, however resulting in increase of end-to-end delay. To mitigate this drawback, the broadcast authentication protocols have been proposed. Concept of optimization of the broadcast authentication protocol DREAM parameters in a special case of fully N-ary tree and general random topology containing the same amount of nodes with regard to delay and energy consumption minimization is showed in the paper. Protocol DREAM was taken as an example of broadcast authenticating protocol to show how Color Petri Nets can be used to create a fully functional model of the protocol.

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Keywords: Authentication, protocol, security, DoS, DREAM, N-ary tree

**P. Pocta**
[references] [full-text]

The Combined Effect of Signal Strength and Background Traffic Load on Speech Quality in IEEE 802.11 WLAN

This paper deals with measurements of the combined effect of signal strength and background traffic load on speech quality in IEEE 802.11 WLAN. The ITU-T G.729AB encoding scheme is deployed in this study and the Distributed Internet Traffic Generator (D-ITG) is used for the purpose of background traffic generation. The speech quality and background traffic load are assessed by means of the accomplished PESQ algorithm and Wireshark network analyzer, respectively. The results show that background traffic load has a bit higher impact on speech quality than signal strength when both effects are available together. Moreover, background traffic load also partially masks the impact of signal strength. The reasons for those findings are particularly discussed. The results also suggest some implications for designers of wireless networks providing VoIP service.

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Keywords: IEEE 802.11, signal strength, background traffic load, speech quality, Perceptual Evaluation of Speech Quality (PESQ)

**Yipeng Liu, Qun Wan, Xiaoli Chu**
[references] [full-text]

Power-Efficient Ultra-Wideband Waveform Design Considering Radio Channel Effects

This paper presents a power-efficient maskconstrained ultra-wideband (UWB) waveform design with radio channel effects taken into consideration. Based on a finite impulse response (FIR) filter, we develop a convex optimization model with respect to the autocorrelation of the filter coefficients to optimize the transmitted signal power spectrum, subject to a regulatory emission mask. To improve power efficiency, effects of transmitter radio frequency (RF) components are included in the optimization of the transmitter-output waveform, and radio propagation effects are considered for obtaining the most efficient waveform at the receiver. Optimum coefficients of the FIR filter are obtained through spectral factorization of their autocorrelations. Simulation results show that the proposed method is able to maximize the transmitted UWB signal power under mask constraints set by regulatory authorities, while mitigating the power loss caused by channel attenuations.

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Keywords: Power efficiency, ultra-wideband (UWB), green communication, radio propagation effect, waveform design

**A. Dziedzic, P. Slobodzian**
[references] [full-text]

Modern Microelectronic Technologies in Fabrication of RFID Tags

This paper presents fabrication of RFID tags, especially antennas for HF band (13.56 MHz), on cheap flexible substrates. The physicochemical, geometrical, DC and AC electrical properties as well as long-term stability (under thermal, moisture-thermal and mechanical exposures) have been characterized for several low-temperature polymer thick-film conductive films made on various paper or foil substrates. Resistance measurement during curing has been used for investigation of polymerization velocity, which is very important for increase of process capacity.

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Keywords: RFID, printed antenna, polymer conductive ink, electrical properties

**J. Pavelka, J. Sikula, M. Tacano, M. Toita**
[references] [full-text]

Activation Energy of RTS Noise

Low frequency noise was measured in silicon MOSFET and GaN and InGaAs based HFET devices with special emphasis on the RTS noise. The RTS (Random Telegraph Signal) dependence on the biasing conditions and temperature was analyzed in order to obtain new information regarding production technology. From the time dependence of the RTS noise voltage the mean time of charge carriers capture and emission by traps in the gate oxide layer was determined as a function of applied gate and drain voltage or electron concentration and then several important trap parameters, such as activation energy and position in the channel could be estimated.

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Keywords: RTS noise, 1/f noise, trap, MOSFET, HFET

**P. Sedlak, J. Majzner, J. Sikula**
[references] [full-text]

Noise in piezoelectric ceramics at the low temperatures

The piezoelectric ceramic belongs to materials with widespread spectrum of applications. It can be found in sensors as well as in ceramic capacitors. The main sources of voltage or current fluctuation in piezoelectric ceramics are thermal noise, polarization noise and low frequency 1/f noise. The observed spectra of fluctuating voltage or current can be very well described by the generalized Nyquist relation for linear dissipative system. In this work, we focused on validity of the Nyquist relation for piezoelectric ceramics in temperatures 150 K-270 K. The electrical impedance and noise spectral density are measured and compared in frequency range 100 kHz - 1 MHz. The measurements were made in thermal stable condition and under equilibrium conditions in the case of noise measurement.

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Keywords: Piezoelectric ceramics, thermal noise, 1/f noise

**E. Prociow, M. Zielinski, K. Sieradzka, J. Domaradzki, D. Kaczmarek**
[references] [full-text]

Electrical and optical study of transparent V-based oxide semiconductors prepared by magnetron sputtering under different conditions

This work is focused on structural, optical and electrical behaviors of vanadium-based oxide thin films prepared by magnetron sputtering under different conditions. Thin films have been deposited on glass substrates from metallic vanadium target at low sputtering pressure. Different working gases: argon/oxygen mixture, and especially pure oxygen gas, have been applied. Results of X-ray diffraction together with optical transmission and temperature- dependent electrical resistivity measurements have been presented. Transmission coefficient, cut-off wavelength and the width of the optical band gap have been calculated from optical measurements. The d.c. resistivity values at room temperature and thermal activation energy have been obtained from electrical investigations. The influence of sputtering process conditions on optical and electrical properties has been discussed.

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- MUSIL, J., BAROCH, P., VLCEK, J., NAM, K. H., HAN, J. G. Reactive magnetron sputtering of thin films: present and trends. Thin Solid Films, 2005, vol. 475, p. 208-218.
- MUSIL, J., VLCEK, J. Magnetron sputtering of hard nanocomposite coatings and their properties. Surf. Coat. Technol., 2001, vol. 142-144, p. 557-566.
- POSADOWSKI, W. M. Pulsed magnetron sputtering of reactive compound. Thin Solid Films, 1999, vol. 343-344, p. 85-89.
- DOMARADZKI, J., KACZMAREK, D., BORKOWSKA, A., SCHMEISSER, D., MUELLER, S., WASIELEWSKI, R., CISZEWSKI, A. Influence of annealing on structure and stoichiometry of europium doped titanium dioxide thin film. Vacuum, 2008, vol. 82/10, p. 1007-1012.
- MESSIER, R., GIRI, A. P., ROY, R. A., Revised structure zone model for thin film physical structure. J. Vac. Sci. Techn. A, 1984, vol. 2, p. 500-503.
- MUSIL, J., KADLEC, S., VALVODA, V., KUZEL, R., CERNY, R. Ion - assisted sputtering of TiN films. Surf. Coat. Technol., 1990, vol. 43–44, p. 259–269.
- KACZMAREK, D., DOMARADZKI, J., WOJCIESZAK, D., WASIELEWSKI, R., BORKOWSKA, A., PROCIOW, E. L., CISZEWSKI, A. Structural investigations of TiO2:Tb thin films by X-ray diffraction and atomic force microscopy. Applied Surface Science, 2008, vol. 254, p. 4303-4307.
- KAID, M. A. Characterization of electrochromic vanadium pentoxide thin films prepared by spray pyrolysis. Egypt. J. Solids, 2006, vol. 29, p. 273-291.
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Keywords: Magnetron sputtering, vanadium oxide, optical properties, electrical properties

**S. Cichon, B. Barda, P. Machac**
[references] [full-text]

Ni and Ni Silicides Ohmic Contacts on N-type 6H-SiC with Medium and Low Doping Level

Ni silicides contacts, which are expected to be advantageous contact materials on SiC, were tested in this work. Prepared contact structures were ohmic with low contact resistivity approximately 8×10-4 Ω cm2 after annealing at 960°C as far as the SiC substrate with a medium doping level was concerned, no matter whether Ni or Ni silicides were used. At lower annealing temperatures, only Schottky behavior was observed by means of I-V characteristics measurements. In the case of SiC substrate with a low doping level, the behavior differed. It was necessary to anneal the structures at 1070°C to see ohmic behavior appearing with resistivities reaching 8×10-3 Ω cm2 and this was valid only for Ni and Ni2Si. Raman spectroscopy measurements confirmed formation of single Ni silicides as expected. It was found that Ni silicides can keep as good resistivity as Ni contacts while they interact with SiC in limited way and their undesirable drop-like morphology is expected to be overcome for example with a covering layer.

- PORTER, L. M., DAVIS, R. F. A critical-review of ohmic and rectifying contacts for silicon-carbide. Materials Science and Engineering B, 1995, vol. 34, no. 2-3, p. 83 – 105.
- TREU, M., RUPP, R., BLASCHITZ, P., HILSENBECK, J. Commercial SiC device processing: Status and requirements with respect to SiC based power devices. Superlattices and Microstructures, 2006, vol. 40, no. 4-6, p. 380 – 387.
- MARINOVA, T., KAKANAKOVA-GEORGIEVA, A., KRASTEV, V., KAKANAKOV, R., NESHEV, M., KASSAMAKOVA, L., NOBLANC, O., ARNODO, C., CASSETTE, S., BRYLINSKI, C., PECZ, B., RADNOCZI, G., VINCZE, G. Nickel based ohmic contacts on SiC. Materials Science and Engineering B, 1997, vol. 46, no. 1-3, p. 223 -226.
- HAN, S. Y., KIM, K. H., KIM, J. K., JANG, H. W., LEE, K. H., KIM, N.-K., KIM, E. D., LEE, J.-L. Ohmic contact formation mechanism of Ni on n-type 4H–SiC. Applied Physics Letters, 2001, vol. 79, no. 12, p. 1816 – 1818.
- GUZIEWICZ, M., PIOTROWSKA, A., KAMINSKA, E., GRASZA, K., DIDUSZKO, R., STONERT, A., TUROS, A., SOCHACKI, M., SZMIDT, J. Ta-Si contacts to n-SiC for high temperatures device. Materials Science and Engineering B, 2006, vol. 135, no. 3, p. 289 – 293.
- DEEB, C., HEUER, A. H. A low-temperature route to thermodynamically stable ohmic contacts to n-type 6H-SiC. Applied Physics Letters, 2004, vol. 84, no. 7, p. 1117 – 1119.
- NAKAMURA, T., SATOH, M. Schottky barrier height of a new ohmic contact NiSi2 to n-type 6H-SiC. Solid-State Electronics, 2002, vol. 46, no. 12, p. 2063 – 2067.
- KUCHUK, A, KLADKO, V., PIOTROWSKA, A., MINIKAYEV, R., STONERT, A., RATAJCZAK, R. Fabrication and characterization of nickel silicide ohmic contacts to n-type 4H silicon carbide. Journal of Physics: Conference Series, 2008, vol. 100, part 4.
- EDMOND, J.A., RYU, J., GLASS, J. T., DAVIS, R. F. Electrical contacts to beta-silicon carbide thin-films. Journal of the Electrochemical Society, 1988, vol. 135, no. 2, p. 359 -362.
- HARIMA, H. Raman scattering characterization on SiC. Microelectronic Engineering, 2006, vol. 83, no. 1, p. 126-129.
- BHASKARAN, M., SRIRAM, S., PEROVA, T. S., ERMAKOV, V., THOROGOOD, G. J., SHORT, K. T., HOLLAND, A. S. In situ micro-Raman analysis and X-ray diffraction of nickel silicide thin films on silicon. Micron, 2009, vol. 40, no. 1, p. 89-93.
- WAN, L., REN, Y., TANG, B., CHENG, X., ZHANG, X., XU, D., LUO, H., HUANG, Y. Polarized Raman spectroscopy study of NiSi film grown on Si(001) substrate. Applied Physics A, 2009, vol. 97, no. 3, p. 693-697.
- CONTI, G., LAZIK, C., URITSKY, Y. Micro-Raman characterization of phase formation and thermal stability of nickel silicide thin films. Microscopy and Microanalysis, 2005, vol. 11, p. 2094 – 2095.
- CAO, Y., NYBORG, L., YI, D.-Q., JELVESTAM, U. Study of reaction process on Ni/4H-SiC contact. Materials Science and Technology, 2006, vol. 22, no. 10, p. 1227 – 1234.
- HUANG, W., ZHANG, L., GAO, Y., JIN, H. Effect of a thin W, Pt, Mo, and Zr interlayer on the thermal stability and electrical characteristics of NiSi. Microelectronic Engineering, 2007, vol. 84, no. 4, p. 678 – 683.
- ZHAO, F. F., ZHENG, J. Z., SHEN, Z. X., OSIPOWICZ, T., GAO, W. Z., CHAN, L. H. Thermal stability study of NiSi and NiSi2 thin films. Microelectronic Engineering, 2004, vol. 71, no. 1, p. 104 – 111.
- BARDA, B., MACHAC, P. Reactions of nickel-based ohmic contacts with n-type 4H silicon carbide. Electroscope (ISSN 1802- 4564). Electronic Devices and Systems IMAPS CS International Conference 2009, Brno (Czech Republic).

Keywords: Silicon carbide, ohmic contact, silicide, Raman

**I. Szendiuch**
[references] [full-text]

Development in Electronic Packaging – Moving to 3D System Configuration

The electronic industry is reducing package dimensions of components as well as complete electronics systems. Surface mount device passives and semiconductor chips have to be mounted together bringing a functional system that must realize the required function with necessary reliability and acceptable price. To make up a reliable and cost effective system, the size and weight is being reduced by employing lower voltages and higher speeds. For example, the typical size of SMD passives 30 years ago was 1206 when they were first introduced. Generally, all components including electrical joints are becoming miniaturized and smaller. The industry is moving toward a reduced size of 0201 and 01005 for passives, new fine pitch packages for actives, but the PCB now feature limits for further integration. System on Package (SOP) is one way to reach the three-dimensional package concept where components will be placed in three-dimensional configuration. A similar concepts are “Package on Package” (PoP) or ”Package in Package” (PiP).

- TUMMALA, R., R. Fundamentals of Microsystems Packaging. New York: McGraw-Hill, 2001.
- BROWN, W., D. Advanced Electronic Packaging. New York: IEEE Press, 1998.
- SZENDIUCH, I., SANDERA, J., BILEK, J. Multi substrate modules – cheap solution for 3D packaging. In Proceedings of the IMAPS Nordic Annual Conference. Stockholm (Sweden), 2002, p. 114 – 122.
- ADAMEK, M., PRASEK, J., NICAK, M. New trends of BGA soldering in education. Electronics, 2009, vol. 18, no. 2, p. 26 - 28.
- ASCHENBRENNER, R. Greetings from IEEE/CPMT. In 30th International Spring Seminar on Electronics Technology ISSE 2007. Cluj Napoca (Romania), 2007.
- Pac Tech – Packaging Technologies. [Online] 2011. Available at: http://www.pactech.com.
- HASKARD, M. R., PITT, K. Thick-film technology and applications. Isle of Man (UK): Electrochemical Publications Ltd., 2004.
- iNEMI, The International Electronics Manufacturing Initiative. [Online] 2009. Available at: http://www.inemi.org/
- TUMMALA, R., SWAMINATHAN, M. Introduction to System on Package. New York: McGraw Hill, 2004.
- HARPER, CH. A. Electric Packaging and Interconnection Handbook. New York: McGraw Hill, 2000.
- PRC Homepage: 3D Systems Packaging Research Center. [Online] 2009. Available at: http://www.prc.gatech.edu/.

Keywords: Electronic Packaging, Integration in Electronics, System on Package (SoP), Package on Package (PoP), 3D packaging.

**L. Brancik, B. Sevcik**
[references] [full-text]

Computer Simulation of Nonuniform MTLs via Implicit Wendroff and State-Variable Methods

The paper deals with techniques for a computer simulation of nonuniform multiconductor transmission lines (MTLs) based on the implicit Wendroff and the statevariable methods. The techniques fall into a class of finitedifference time-domain (FDTD) methods useful to solve various electromagnetic systems. Their basic variants are extended and modified to enable solving both voltage and current distributions along nonuniform MTL’s wires and their sensitivities with respect to lumped and distributed parameters. An experimental error analysis is performed based on the Thomson cable whose analytical solutions are known, and some examples of simulation of both uniform and nonuniform MTLs are presented. Based on the Matlab language programme, CPU times are analyzed to compare efficiency of the methods. Some results for nonlinear MTLs simulation are presented as well.

- HALL, S. H., HECK, H. L. Advanced Signal Integrity for High- Speed Digital Designs. Hoboken: John Wiley & Sons, 2009.
- BENESOVA, Z., MAYER, D. Overvoltage phenomena on transmission lines. In Proc. of the XI. ISTET’2001. Linz (Austria), 2001, p. 1 - 4.
- BENESOVA, Z., KOTLAN, V. Propagation of surge waves on interconnected transmission lines induced by lightning stroke. Acta Technica CSAV, 2006, vol. 51, no. 3, p. 301 - 316.
- BRANCIK, L. Transient and sensitivity analysis of uniform multiconductor transmission lines via FDTD methods. In Proc. of the XV. ISTET’2009. Lubeck (Germany), 2009, p. 109 - 113.
- BRANCIK, L. Time-domain analysis of multiconductor transmission lines per implicit Wendroff method. In Proc. of Int. IMAPS EDS 2010 Conference. Brno (Czech Republic), 2010, p. 45 - 50.
- CHENG, C. K., LILLIS, J., LIN, S., CHANG, N. Interconnect Analysis and Synthesis. New York: John Wiley & Sons, 2000.
- BRANCIK, L. Sensitivity in multiconductor transmission line lumped-parameter models. In Proc. of the 31st International Conference TSP’2008. Paradfurdo (Hungary), 2008, p. 1 - 4.
- BRANCIK, L. Transient and sensitivity analysis at semi-discrete multiconductor transmission line models. Electroscope [online]. Cited 2010-12-04. Available at: http://www.electroscope.zcu.cz.
- SULLIVAN, D. M. Electromagnetic Simulation using the FDTD Method. New York: IEEE Press, 2000.
- SUI, W. Time-Domain Computer Analysis of Nonlinear Hybrid Systems. New York: CRC Press, 2002.
- DOU, L., DOU, J. Sensitivity analysis of lossy nonuniform multiconductor transmission lines based on Lax-Wendroff technique. Int. J. Numer. Model., 2010, vol. 23, no.3, p. 165 - 182.
- DEDKOVA, J., BRANCIK, L. Laplace transform and FDTD approach applied to MTL simulation. Piers Online, 2008, vol. 4, no. 1, p. 16 - 20.
- PAUL, C. R. Analysis of Multiconductor Transmission Lines. New York: John Wiley & Sons, 2008.
- GANTMACHER, F. R. The Theory of Matrices. Providence: AMS Chelsea Publishing, 2000.
- MOLER, C., LOAN, C. V. Nineteen dubious ways to compute the exponential of a matrix, twenty-five years later. SIAM Review, 2003, vol. 45, no. 1, p. 1 - 46.
- BRANCIK, L. Matlab programs for matrix exponential function derivative evaluation. In Proc. of Technical Computing Prague 2008. Prague (Czech Republic), 2008, p. 17 - 24.
- BRANCIK, L. Matlab oriented matrix Laplace transforms inversion for distributed systems simulation. In Proc. of the 12th Int. Conf. Radioelektronika. Bratislava (Slovakia), 2002, p. 114 - 117.
- GRIFFITH, J. R., NAKHLA, M. S. Time-domain analysis of lossy coupled transmission lines. IEEE Transactions on Microwave Theory and Techniques, 1990, vol. 38, no. 10, p. 1480 - 1487.

Keywords: Multiconductor transmission line, Wendroff method, state-variable method, sensitivity analysis, Matlab

**D. Biolek, Z. Biolek, V. Biolkova**
[references] [full-text]

Behavioral Modeling of Memcapacitor

Two behavioral models of memcapacitor are developed and implemented in SPICE-compatible simulators. Both models are related to the charge-controlled memcapacitor, the capacitance of which is controlled by the amount of electric charge conveyed through it. The first model starts from the state description of memcapacitor whereas the second one uses the memcapacitor constitutive relation as the only input data. Results of transient analyses clearly show the basic fingerprints of the memcapacitor.

- CHUA, L.O. Memristor–the missing circuit element. IEEE Transactions on Circuit Theory, 1971, vol. CT-18, no. 5, p. 507 – 519.
- STRUKOV, D.B., SNIDER, G.S., STEWART, D.R., WILLIAMS, R.S. The missing memristor found. Nature, 2008, vol.453, p.80–83
- CHUA, L.O., KANG, S.M. Memristive devices and systems. Proceedings of the IEEE, 1976, vol. 64, no. 2, p. 209 – 223.
- BIOLEK, Z., BIOLEK, D., BIOLKOVA, V. SPICE model of memristor with nonlinear dopant drift. Radioengineering, 2009, vol. 18, no. 2, p. 210 – 214.
- BIOLEK, D., BIOLEK, Z., BIOLKOVA, V. SPICE modelling of memcapacitor. Electron. Lett., 2010, vol. 46, no. 7, p. 520 – 522.
- BIOLEK, D., BIOLEK, Z., BIOLKOVA, V. SPICE Modeling of Memristive, Memcapacitative and Meminductive Systems. In Proceedings of ECCTD '09. Antalya (Turkey), 2009, p. 249 – 252.
- PERSHIN, Y.V., Di VENTRA, M. Memristive circuits simulate memcapacitors and meminductors. Electronics Letters, 2010, vol. 46, no. 7, p. 517 – 518.
- BIOLEK, D., BIOLKOVA, V. Mutator for transforming memristor into memcapacitor. Electronics Letters, 2010, vol. 46, no. 21, p. 1428 – 1429.
- BIOLEK, D., BIOLKOVA, V., KOLKA, Z. Mutators simulating memcapacitors and meminductors. In Proceedings of 2010 Asia Pacific Conference on Circuits and Systems (APPCAS 2010). Kuala Lumpur (Malaysia), 2010. To be published.
- PERSHIN, Y.V, Di VENTRA, M. Practical approach to programmable analog circuits with memristors. IEEE Transactions on Circuit and Systems – I, 2010, vol. 57, no. 8, p. 1857 – 1864.
- VALSA, J., BIOLEK, D., BIOLEK, Z. An analogue model of the memristor. International Journal of Numerical Modelling, 2010, published online: 25 August 2010, DOI: 10.1002/jnm.786.
- Micro-Cap homepage: www.spectrum-software.com.
- JOGLEKAR, Y.N., WOLF, S.J. The elusive memristor: properties of basic electrical circuits. European Journal of Physics, 2009, vol. 30, no. 4, p. 661 – 675.
- KAVEHEI, O., IQBAL, A., KIM, Y.S., ESHRAGHIAN, K., Al- SARAWI, S.F., ABBOT, D. The fourth element: characteristics, modelling, and electromagnetic theory of the memristor. Proceedings of the Royal Society A. Published online 17 March 2010, p. 1 – 28. DOI: 10.1098/rspa.2009.0553.
- CHUA, L.O. Nonlinear circuit foundations for nanodevices. Part I: The four-element torus. Proceedings of the IEEE, 2003, vol. 91, no. 11, p. 1830 – 1859.

Keywords: Memcapacitor, memristor, SPICE, constitutive relation

**V. Kledrowetz, J. Haze**
[references] [full-text]

Basic Block of Pipelined ADC Design Requirements

The paper describes design requirements of a basic stage (called MDAC - Multiplying Digital-to- Analog Converter) of a pipelined ADC. There exist error sources such as finite DC gain of opamp, capacitor mismatch, thermal noise, etc., arising when the switched capacitor (SC) technique and CMOS technology are used. These non-idealities are explained and their influences on overall parameters of a pipelined ADC are studied. The pipelined ADC including non-idealities was modeled in MATLAB - Simulink simulation environment.

- KLEDROWETZ, V., HAZE, J. Multiplying digital-to-analog converter with 1,5 and 2,5 bit resolution - case study. In Proceedings of 15th International EDS Conference 2008. Brno (Czech Republic), 2008, p. 326 - 331.
- CHANG-HYUK, CH. A Power Optimized Pipelined Analog-to- Digital Converter Design in Deep Sub-Micron CMOSmos Technology. Dissertation, 2005.
- OSHIMA, T., TAKAHASHI, T., YAMAWAKI, T. 23-mW 50- MS/s 10-bit pipeline A/D converter with nonlinear LMS foreground calibration. In IEEE International Symposium on Circuits and Systems ISCAS 2009. Taipei (Taiwan), p. 960 - 963.
- ALLEN, P., E., HOLBERG, D., R. CMOS Analog Circuit Design. Oxford University Press, 2002.
- BYUNG-MOO, M., KIM, P., BOWMAN, F. W., BOISVERT, D. M., AUDE, A. J. A 69-mW 10-bit 80-MSample/s pipelined CMOS ADC. IEEE Journal of Solid-State Circuits, 2003, vol. 38, no. 12, p. 2031 - 2039.
- HEE CHEOL, CH., HO-JIN P., SUNG-SIK, H., SHIN-KYU, B., JAE-WHUI, K,. CHUNG, P. A 1.5 V 10-bit 25 MSPS pipelined A/D converter. The First IEEE Asia Pacific Conference on ASICs. Seoul (South Korea), 1999, p. 170 - 173.
- WALTARI, M. E., HALONEN, A. I. Circuit Techniques for Low- Voltage and High-Speed A/D Converter. Dordrecht (The Netherlands): Kluwer Academic Publishers, 2002.
- EL-SANKARY, K., SAWAN, M. Background capacitor mismatch calibration for pipelined ADC. In Proceedings of the IEEE Midwest Symposium on Circuits and Systems. Cairo (Egypt), 2003, p.164 - 167.
- WANG, H., WANG, X., HURST, P., LEWIS, S. Nested digital background calibration of a 12-bit pipelined ADC without an input SHA. IEEE Journal of Solid-State Circuits, 2004, vol. 44, no. 10, p.164 - 167.
- NAN, S., HAE-SEUNG, L., DONHEE, H. Digital background calibration in pipelined ADCs using commutated feedback capacitor switching. IEEE Transactions on Circuits and Systems, 2008, vol. 55, no. 9, p. 877 - 881.
- IMRAN, A. Pipelined ADC Design and Enhancement Techniques. Berlin: Springer, 2010.

Keywords: Pipelined ADC, MDAC, SC technique, MATLAB model, thermal noise, opamp

**T. Urban, O. Subrt, P. Martinek**
[references] [full-text]

Analysis and Design Procedure of LVLP Sub-bandgap Reference - Development and Results

This work presents an thorough analysis and design of a low-voltage low-power voltage reference circuit with sub-bandgap output voltage. The outcome of the analysis and the resulting design rules are universal and it is supposed to be general and suitable for similar topologies with just minor modifications. The general analysis is followed by a selection of specific topology. The given topology is analyzed for particular parameters which are standard industrial circuit specifications. These parameters are mathematically expressed, some are simplified and equivalent circuits are used. The analysis and proposed design procedure focuses mainly on versatility of the IP block. The features of the circuit suit to low-voltage low-power design with less than 10μA supply current draw at 1.3V supply voltage. For testing purposes a complex transistor level design was created and verified in wide range of supply voltages (1.3 to 3.3V) and temperatures (-45 to 95°C) all in concrete 0.35μm IC design process using Mentor Graphics® and Cadence® software.

- BANBA, H. et al. A CMOS bandgap reference circuit with sub-1-V operation. IEEE Journal of Solid-State Circuits, 1999, vol. 34, no. 5, p. 670 - 674.
- URBAN, T. Integrated Low-Power Voltage Reference Block. Master thesis. Prague: CTU FEE, 2010.
- URBAN, T. Versatile sub-bandgap reference IP core. In IEEE International Symposium on Design & Diagnostics of Electronic Circuits & Systems. Vienna (Austria), 2010, p. 393 - 398.
- SEGUPTA, S. et al. Design considerations in bandgap references over process variations. In IEEE International Symposium on Circuits and Systems. Kobe (Japan), 2005, vol. 4, p. 3869 – 3872.
- TADEPARTHY, P. A CMOS bandgap reference with correction for device-to-device variation. IEEE International Symposium on Circuits and Systems. Vancouver (Canada), 2004, vol. 1, p. 397 – 400.
- YTTERDAL, T. CMOS bandgap voltage reference circuit for supply voltages down to 0.6V. Electronics Letters, 2003, vol. 39, no. 20, p. 1427 – 1428.
- SZE, S. M. Physics of Semiconductor Devices. New York: Wiley, 2006.
- ALLEN, P. E., HOLBERG, P. E. CMOS Analog Circuit Design. 2nd ed. Oxford University Press, 2002.
- URBAN, T. Analysis and design procedure of LVLP sub-bandgap reference. IMAPS conference on Electronic Devices and Systems. Brno (Czech Republic), 2010.

Keywords: Low-voltage, Low-power, Bandgap reference, step-by-step design

**J. Bajer, A. Lahiri, D. Biolek**
[references] [full-text]

Current-Mode CCII+ Based Oscillator Circuits using a Conventional and a Modified Wien-Bridge with All Capacitors Grounded

The paper deals with a pair of current-mode sine-wave oscillator circuits. Both these circuits are implemented using positive second-generation current conveyors (CCII+). The principle of the first oscillator is based on a conventional Wien-bridge network. However, this implementation suffers from the use of a floating capacitor, which can be unacceptable in the case of on-chip integration. This drawback is solved in the second variant via a slight modification of the Wien-bridge network, which then allows the use of all capacitors grounded. The modified circuit version was manufactured by means of the socalled diamond transistors, which play the role of CCII+ active building blocks. The circuit behavior was analyzed theoretically, with particular emphasis on the identification of real effects and their elimination, and subsequently verified experimentally. The experimental results are included in the paper.

- SENANI, R., GUPTA, S. S. Novel SRCOs using first generation current conveyor. Int. Journal of Electronics, 2000, vol. 87, no. 10, p. 1187-1192.
- ABUELMA'ATTI, M. T., AL-GHUMAIZ, A. A-A. Novel currentconveyor- based single-element-controlled oscillator employing grounded resistors and capacitors. Active and Passive Electronic Components, 1995, vol. 17, no. 4, p. 203-206.
- MINHAJ, N. CCII-based single-element controlled quadrature oscillators employing grounded passive components. Int. Journal of Recent Trends in Engineering, 2009, vol. 1, no. 3, p. 294-296.
- SOLIMAN, A. M. Synthesis of grounded capacitor and grounded resistor oscillators. Journal of the Franklin Institute, 1999, vol. 336, no. 4, p. 735-746.
- MARTINEZ, P. A., SABADELL, J., ALDEA, C., CELMA, S. Variable frequency sinusoidal oscillators based on CCII+. IEEE Transactions on Circuits and Systems I: Fundamental Theory and Applications, 1999, vol. 46, no. 11, p. 1386 – 1390.
- NANDI, R. Wien bridge oscillators using current conveyors. Proceedings of the IEEE, 1977, vol. 65, no. 11, p. 1608-1609.
- SOLIMAN, A. M. Novel generation method of current mode Wien-type oscillators using current conveyors. Int. Journal of Electronics, 1998, vol. 85, no. 6, p. 737–747.
- MARTINEZ, P. A., CELMA, S., GUTIERREZ, I. Wien-type oscillators using CCII+. Analog Integrated Circuits and Signal Processing, 1995, vol. 7, no. 2, p. 139–147.
- ABUELMA’ATTI, M. T, HUMOOD, N. A. Two new minimumcomponent Wien bridge oscillators using current conveyors. Int. Journal of Electronics, 1987, vol. 63, p. 669-672.
- SVOBODA, J. A., McGORY, L., WEBB, S. Applications of commercially available current conveyor. Int. Journal of Electronics, 1991, vol. 70, no. 1, p. 159-164.
- CELMA, S., MARTINEZ, P. A., CARLOSENA, A. Current feedback amplifiers based sinusoidal oscillators. IEEE Transactions on Circuits and Systems I: Fundamental Theory and Applications, 1994, vol. 41, no. 12, p. 906-908.
- MARTINEZ, P. A., CELMA, S., SABADELL, J. Designing sinusoidal oscillators with current-feedback amplifiers. Int. Journal of Electronics, 1996, vol. 80, no. 5, p. 637-646.
- SENANI, R. On equivalent forms of single-op-amp sinusoidal RC oscillators. IEEE Trans. on Circuits and Systems I: Fundamental Theory and Applications, 1994, vol. 41, no. 10, p. 617-624.
- OP860. Wide Bandwidth Operational Transconductance Amplifier (OTA) and Buffer, Datasheet, Texas Instruments, SBOS331B, June 2006.
- BIOLEK, D., et al. Z Copy - Controlled Gain - Current Differencing Buffered Amplifier and its applications. Int. Journal of Circuit Theory and Applications, 2010. Published online: March 22, 2010 in Wiley Interscience (www.interscience.wiley.com).
- BAJER, J., VAVRA, J., BIOLEK, D. A new building block for analog signal processing: current follower/inverter buffered transconductance amplifier. In Proc. of the IEEE conf. Ph.D. Research in Microelectronics and Electronics PRIME 2009, July 2009, p. 136-139.
- BIOLEK, D., et al. Single-input multi-output resistorless currentmode biquad. In Proc. of ECCTD '09, European Conference on Circuit Theory and Design. August 2009, p. 225-228.
- BIOLKOVA, V., KOLKA, Z., BIOLEK, D. Fully balanced voltage differencing buffered amplifier and its applications. In Proc. of the 52nd MWSCAS, August 2009, p. 45-48.
- BIOLEK, D., BIOLKOVA, V. Implementation of active elements for analog signal processing by diamond transistors. In Proc. of the Int. Conf. EDS-IMAPS 2009, September 2009, p. 304-309.
- LINDBERG, E. The Wien bridge oscillator family. In Proc. of ICSES'06 - Int. Conf. on Signals and Electronic Systems, 2006, p. 189-192.
- KOLKA, Z., BIOLEK, D., BIOLKOVA, V. Symbolic analysis of linear circuits with modern active elements. WSEAS Transactions on Electronics, 2008, vol. 5, no. 6, p. 88-96.
- PALUMBO, G., PENNISI, M., PENNISI, S. Wien-type oscillators: Evaluation and optimization of harmonic distortion. IEEE Transactions on Circuits and Systems II: Express Briefs, 2008, vol. 55, no. 7, p. 628-632.

Keywords: Diamond transistor, Wien-bridge oscillator, current-mode, current conveyor

**Z. Kolka, M. Vlk, M. Horak**
[references] [full-text]

Topology Reduction for Approximate Symbolic Analysis

The paper deals with a procedure for approximate symbolic analysis of linear circuits based on simplifying the circuit model. The procedure consists of two main steps. First, network elements whose influence on the circuit function is negligible are completely removed, i.e. their parameters are removed from the resulting symbolic formula. The second step consists in modifying the voltage and current graphs in order to decrease the number of common spanning trees. The influence of each modification of the circuit model is ranked numerically. A fast method based on the use of cofactors is presented. It allows evaluating all the prospective simplifications using at most two matrix inversions per one frequency point.

- SOMMER, R., HALFMANN, T., BROZ, J. Automated behavioral modeling and analytical model-order reduction by application of symbolic circuit analysis for multi-physical systems. Simulation Modelling Practice and Theory, 2008, no. 16, p. 1024–1039.
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- LIN, P. M. Symbolic Network Analysis. Amsterdam: Elsevier, 1991.
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- MAYEDA, W, SESHU, S. Topological Formulas for Network Functions. Eng. Exp. Station, University of Illinois, Bulletin 446, Urbana, 1957.
- PALUMBO, G. Bipolar current feedback amplifiers: Compensation guidelines. Int. J. Analog Integrated Circuits and Signal Processing, May 1999, vol. 19, no. 2, p. 107–114.

Keywords: Symbolic analysis, two-graph method, circuit reduction, linear circuits, frequency domain.

**J. Bauer, J. Lettl**
[references] [full-text]

Solar Power Station Output Inverter Control Design

The photovoltaic applications spreads in these days fast, therefore they also undergo great development. Because the amount of the energy obtained from the panel depends on the surrounding conditions, as intensity of the sun exposure or the temperature of the solar array, the converter must be connected to the panel output. The Solar system equipped with inverter can supply small loads like notebooks, mobile chargers etc. in the places where the supplying network is not present. Or the system can be used as a generator and it shall deliver energy to the supply network. Each type of the application has different requirements on the converter and its control algorithm. But for all of them the one thing is common – the maximal efficiency. The paper focuses on design and simulation of the low power inverter that acts as output part of the whole converter. In the paper the design of the control algorithm of the inverter for both types of inverter application – for islanding mode and for operation on the supply grid – is discussed. Attention is also paid to the design of the output filter that should reduce negative side effects of the converter on the supply network.

- LISERRE, M., BLAABJERG, F., HANSEN, S. Design and control of an lcl-filter based three-phase active rectifier. In Industry Applications Conference, 2001. Thirty-Sixth IAS Annual Meeting. Conference Record of the 2001 IEEE, vol. 1, 2001.
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- DAHONO, P. A. A method to damp oscillations on the input LC filter of current-type ac-dc PWM converters by using a virtual resistor. In Telecommunications Energy Conference INTELEC’03, 2003.
- da SILVA, O., NOVOCHADLO, S. A., MODESTO, R. Singlephase PLL structure using modified p-q theory for utility connected system. In Proc. of the 39th Power Electronics Specialists Conference PESC 2008. Rhodes (Greece), 2008.
- CIOBOTARU, M., TEODORESCU, R., BLAABJERG, F. A new single-phase PLL structure based on second order generalized integrator. In Proc. of the 37th Power Electronics Specialists Conference PESC 2006.
- FRANKE, W. T., BENZ, Ch., FUCHS, F. W. Low voltage ride through capability of a 5kW grid-tied solar inverter. In Proceedings of the 14th International Power Electronic and Motion Control Conference. Ohrid (Macedonia), 2010.
- SUUL, J. A., JLOKELSOY, K., MIDSTUND, T., UNDELAND, T. Synchronous reference frame hysteresis current control for grid converter applications. In Proceedings of the 14th International Power Electronic and Motion Control Conference. Ohrid (Macedonia), 2010.
- KADRI, R., GAUBERT, J.-P., CHAMPENOIS, G. Design of a single-phase grid-connected photovoltaic system based on deadbeat current control with LCL filter. In Proceedings of the 14th International Power Electronic and Motion Control Conference. Ohrid (Macedonia), 2010.
- SEHIRLI, E., ALTINAY, M. Control of LCL filter based voltage source converter. In Proceedings of the 14th International Power Electronic and Motion Control Conference. Ohrid (Macedonia), 2010.

Keywords: Voltage source inverter, L-C-L filter, hysteresis controller, PWM

**K. Pitra, Z. Raida**
[references] [full-text]

Planar Millimeter-Wave Antennas: A Comparative Study

The paper describes the design and the experimental verification of three types of wideband antennas. Attention is turned to the bow-tie antenna, the Vivaldi antenna and the spiral antenna designed for the operation at millimeter waves. Bandwidth, input impedance, gain, and directivity pattern are the investigated parameters. Antennas are compared considering computer simulations in CST Microwave Studio and measured data.

- PITRA, K. Antennas for Millimetre-Wave Band. Master’s thesis, Brno: Brno University of Technology, 2010.
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- HUDLICKA, M. Coplanar Antenna with Leaky Wave. Master’s thesis. Prague: Czech Technical University in Prague, 2004.
- ABBOSH, A. Directive antenna for ultra-wideband medical imaging systems. International Journal on Antennas and Propagation, 2008, vol. 2008, Article ID 854012.
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- PITRA, K., RAIDA, Z. Wideband feeders for millimeter-wave horn antennas. In Proceedings of the 15th Conference on Microwave Techniques, COMITE. Brno (Czech Republic), 2010, p. 39 – 41.

Keywords: Vivaldi antenna, bow-tie antenna, spiral antenna, ultra-wideband (UWB) communication, millimeter waves.

**P. Piksa, S. Zvanovec, P. Cerny**
[references] [full-text]

Elliptic and Hyperbolic Dielectric Lens Antennas in mm-Waves

Dielectric lenses can substantially improve antenna parameters, especially the planarity of radiated waves and the antenna gain. The paper deals with their application in millimeter-wave band. The main goal concerns the introduction of characteristics and differences between the most commonly used types of dielectric lens antennas, i.e. elliptic and hyperbolic. Their particular features as well as behavior of radiating systems incorporating the lenses are investigated. Specific features of these lenses are discussed for both, near-field and farfield based on simulation and measurement results.

- ZVANOVEC, S., PIKSA, P., CERNY, P., MAZANEK, M., PECHAC, P. Gas attenuation measurement by utilization of Fabry- Perot resonator. In Proceedings of the 2nd European Conference on Antennas and Propagation. Edinburgh (UK), 2007.
- PIKSA, P., CERNY, P., ZVANOVEC, S., MAZANEK, M., URBAN, S. Dielectric lens utilization for Fabry-Perot resonator optimal coupling. In Proceedings of the European Microwave Week 2008 "Bridging Gaps" Conference. Amsterdam (Netherlands), 2008, p. 955 - 958.
- ZVANOVEC, S., CERNY, P., PIKSA, P., KORINEK, T., PECHAC, P., MAZANEK, M., VARGA, J., KOUBEK, J., URBAN, S. The use of the Fabry-Perot interferometer for high resolution microwave spectroscopy. Journal of Molecular Spectroscopy, 2009, vol. 256, no. 1, p. 141 - 145.
- PIKSA, P., CERNY, P., ZVANOVEC, S., MAZANEK, M. Optimization of beam focusing into the Stark´s cell for mm-wave spectroscopy. In Proceedings of the 2nd European Conference on Antennas and Propagation. Edinburgh (UK), 2007.
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Keywords: Dielectric lens antennas, elliptic, hyperbolic, millimeter wave antennas, millimeter wave measurements.

**M. Randus, K. Hoffmann**
[references] [full-text]

Microwave Impedance Measurement for Nanoelectronics

The rapid progress in nanoelectronics showed an urgent need for microwave measurement of impedances extremely different from the 50Ω reference impedance of measurement instruments. In commonly used methods input impedance or admittance of a device under test (DUT) is derived from measured value of its reflection coefficient causing serious accuracy problems for very high and very low impedances due to insufficient sensitivity of the reflection coefficient to impedance of the DUT. This paper brings theoretical description and experimental verification of a method developed especially for measurement of extreme impedances. The method can significantly improve measurement sensitivity and reduce errors caused by the VNA. It is based on subtraction (or addition) of a reference reflection coefficient and the reflection coefficient of the DUT by a passive network, amplifying the resulting signal by an amplifier and measuring the amplified signal as a transmission coefficient by a common vector network analyzer (VNA). A suitable calibration technique is also presented.

- McEUEN, P. L., FUHRER, M. S., PARK, H. Single-walled carbon nanotube electronics. IEEE Transactions on Nanotechnology, 2002, vol. 1, no. 1, p. 78 - 85.
- BURKE, P. J., YU, Z., LI, S, RUTHERGLEN C. Nanotube technology for microwave applications. In Proceedings of the MTT-S International Microwave Symposium. Long Beach (CA, USA), 2005, p. 12 - 17.
- MOSLEY, L. E. Capacitor impedance needs for future microprocessors. In Proceedings of the CARTS USA 2006 Conference. Orlando (FL, USA), 2006.
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- RICHTER, M., TANBAKUCHI, H., WHITENER, M. Design of scanning capacitance microscope. In Proceedings of the 68th ARFTG Microwave Measurement Symposium. Broomfield (CO, USA), 2006.
- BAHL, I., BHARTIA, P. Microwave Solid State Circuit Design. 2nd ed. Hoboken: Wiley, 2003.
- Agilent Technologies, USA. Specifying Calibration Standards and Kits for Agilent Vector Network Analyzers (application note). 42 pages. [Online] Cited 2010-09-21. Available at: http://www.cp.literature.agilent.com/litweb/pdf/5989-4840en.pdf.
- Mini-Circuits, USA. Amplifiers – Surface Mount Monolithic Gain Blocks (selection guide). [Online] Cited 2010-09-21. Available at: http://www.mini-circuits.com/products/ /amplifiers_monolithic.html.

Keywords: calibration, impedance measurement, microwave circuits, microwave measurements, nanotechnology

**L. Sorokosz, W. Zieniutycz, M. Pergol, M. Mazur**
[references] [full-text]

Mutual Coupling Between IFF/SSR Microstrip Antennas with Reduced Transversal Size - Experimental Study

Mutual coupling between IFF/SSR microstrip antennas is investigated experimentally in this paper. At the begining configuration and performance of isolated microstrip antenna fed by H-shaped coupling slot is presented. Next, the vertical and horizontal arrangement of the microstrip antennas array were investigated. The measurements of return loss and coupling coefficients at two operating frequencies for the two orthogonal planes are presented and compared with the results of numerical calculations, showing satisfactory agreement.

- STEVENS, M. Secondary Surveillance Radar, Artech House, 1988.
- VAN LIL, E., VAN DE CAPELLE, A. Transmission line model for mutual coupling between microstrip antennas. IEEE Transactions on Antennas and Propagation, 1984, vol. 32, no. 8, p. 816 - 821.
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- VANDENBOSCH, G. A. E., DEMUYNCK, F. J. The expansion wave concept: Part II, A new way to model mutual coupling in microstrip arrays. IEEE Transanctions on Antennas and Propagation, 1998, vol. 46, no. 3, p. 407 - 413.
- JEDLICKA, R. P., POE, M. T., CARVER, K. R. Measured mutual coupling between microstrip antennas. IEEE Transanctions on Antennas and Propagation, 1981, vol. 29, no. 1, p. 147 - 149.
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Keywords: mutual coupling, microstrip antenna arrays, IFF/SRR systems, patch antenna

**D. Wolansky, R. Tkadlec**
[references] [full-text]

Coaxial Filters Optimization Using Tuning Space Mapping in CST Studio

This paper deals with the optimization of coaxial filters using Tuning Space Mapping (TSM) method implemented to CST environment. The function of fine and coarse model and their link between each other is explained. In addition, supporting macros programmed in VBA language, which are used for maximum efficiency of the optimization from the user´s point of view, are mentioned. Macros are programmed in CST and are also used for automatic calibration constants determination and for automatic calibration process between the coarse model and the fine model. The whole algorithm is illustrated on the particular seven-order filter design and optimized results are compared to measured ones.

- MENG, J., KOZIEL, S., BANDLER, J. W., BAKR, M. H., CHENG, Q. S. Tuning-Space Mapping: A novel technique for engineering design optimization. In Microwave Symposium Digest, 2008 IEEE MTT-S International. Atlanta (GA), 2008, p. 991-994.
- STEPHENS, R. Visual Basic 2005 Programmer´s Reference. Wiley Publishing, Inc., 2005.
- MATTHAEI, G., YOUNG, L., JONES, E. M. T. Microwave Filters, Impedance Matching Networks, and Coupling Structures. Norwood: Artech House, 1980.
- CHEN, W. K. The Circuits and Filters Handbook. Second Edition (Electrical Engineering Handbook). CRC Press, 2002.

Keywords: Tuning Space Mapping, optimization, fine model, coarse model, VBA language, CST

**J. Drinovsky, Z. Kejik, V. Ruzek, J. Zachar, J. Svacina**
[references] [full-text]

Insertion Loss Estimation of EMI Filters in Unmatched Input/Output Impedance System

One of the problems in the design of powerline EMI filters is the uncertainty and ambiguity of their source/load impedances which results in breach of expected filter parameters in a real installation. The paper presents a simple technique for prediction of insertion loss limit values of EMI filters working in arbitrary unmatched mains line impedance systems.

- CHRISTOPOULOS, CH. Principles and Techniques of Electromagnetic Compatibility. Boca Raton (USA): CRC Press, 2001.
- HABIGER, E. Elektromagnetische Vertr¨aglichkeit. Hedielberg (Germany): H¨uthig Buch Verlag, 1992.
- MALACK, J. A., ENGRTROM, J. R. RF Impedance of United States and European power lines. IEEE Trans. on Electromagnetic Compatibility, 1976, vol. 18, no. 1, p. 36-38.
- Schaffner, Switzerland. Catalogue data of EMI filters (data sheets). 6 pages. [online] Cited 2010-09-25. Available at http://www.schaffner.com/.
- CSN CISPR 17: Methods of Measurement of the Suppression Characteristics of Passive Radio Interference Filters and Suppression Components. Czech Technical Standard. . Prague: Czech Normalization Institute, 2000. (in Czech).

Keywords: EMI mains filter, insertion loss, estimation, impedance termination, unmatched impedance system

**S. Rupcic, V. Mandric, D. Zagar**
[references] [full-text]

Reduction of Sidelobes by Nonuniform Elements Spacing of a Spherical Antenna Array

This paper presents a significant sidelobe reduction if nonuniform elevational spacing of antenna elements on the sphere is used. Antenna elements are progressively phased with a uniform amplitude excitation. The calculation of the required element position is presented. The achieved sidelobe level reduction with unequally spaced arrays could reach even more than 20dB difference with regard to the first significant sidelobe level of equally spaced arrays. By this method, arrays have the ability to produce the desired radiation pattern and could satisfy requirements for many applications.

- MOLISCH, A.-F. Wireless Communication. John Wiley & Sons, LTD, IEEE Communication Society, 2005.
- UNZ, H. Linear arrays with arbitrarily distributed elements. IRE Transactions on Antennas and Propagation, March 1960, vol. AP- 8, p. 222 - 223.
- KING, D. D., PACKARD, R. F., THOMAS, R. K. Unequally spaced, broad-band antenna arrays. IRE Transactions on Antennas and Propagation, July 1960, vol. AP-8, p. 380 - 385.
- SANDLER, S. S. Some equivalence between equally and nonequally spaced arrays. IRE Transactions on Antennas and Propagation, March 1961, vol. AP-9, p. 496-500.
- HARRINGTON, R.-F. Sidelobe reduction by nonuniform element spacing. IRE Transactions on Antennas and Propagation, March 1961, p. 187 - 192.
- ANDREASEN, M. G. Linear arrays with variable interelement spacing. IRE Transactions on Antennas and Propagation, March 1962, vol. AP-10, p. 137 - 143.
- ISHIMARU, A. Theory of unequally-spaced arrays. IRE Transactions on Antennas and Propagation, November 1962, vol. AP-8, p. 691 - 702.
- HODJAT, F., HOVANESSIAN, A. A. Nonuniformly spaced linear and planar array antennas for sidelobe reduction. IEEE Transactions on Antennas and Propagation, March 1978, vol. AP- 26, no. 2, p. 198 - 204.
- JARSKE, P., SARAMAKI, T., MITRA, S. K., NEUYO, Y. On properties and design of nonuniformly spaced linear arrays. IEEE Transactions on Acoustics, Speech and Signal Processing, March 1988, vol. 36, no. 3, p. 372 - 380.
- POZAR, D. M., KAUFMAN, B. Design considerations for low sidelobe microstrip arrays. IEEE Transactions on Antennas and Propagation, August 1990, vol. 38, no. 8, p. 1176 – 1185.
- JEFFERS, J. L., BOUCHER, S. G. Optimum unequally spaced arrays and their amplitude shading. In Proceedings of Ultrasonics Symposium, November 1995, vol. 2, p. 965 - 969.
- KUMMAR, B. P., BRANNER, G. R. Generalized analytical technique for the synthesis of unequally spaced arrays with linear, planar, cylindrical or spherical geometry. IEEE Transactions on Antennas and Propagation, February 2005, vol. 53, no. 2, p. 621-634.
- SHIHAB, M., NAJJAR, Y., DIB, N., KHODIER, M. Design of non-uniform circular antenna array using Particle Swarm Optimization. Journal of Electrical Engineering, 2008, vol. 59, no. 4, p. 216 – 220.
- ABDOLEE, R., VAKILIAN, V., RAHMAN, T. A. Elements space and amplitude perturbation using Genetic Algorithm for antenna sidelobe cancellation. Signal Processing: An International Journal (SPIJ), March/April 2008, vol. 2, no. 2, p. 10 – 16.
- BEVELAQUA, P. J., BALANIS, C. A. Geometry and weight optimization for minimizing sidelobes in wideband planar arrays. IEEE Transactions on Antennas and Propagation, April 2009, vol. 57, no. 4, p. 1285 – 1289.
- TAM, W. T., LUK, K. M. Resonance in spherical-circular microstrip structures. IEEE Transactions on Microwave Theory and Technique, April 1991, vol. MTT-39, p. 700 - 704.
- LEIJON, R. Radiation from mobile phone antennas close to the human body. Technical Report No. 270L, Dept. of Microwave Technology, Chalmers Univ. of Technology, Gothenburg, Aug. 1997.
- RUPCIC, S., MANDRIC, V., RIMAC-DRLJE, S. Fabrication errors influence on the spherical array radiation pattern. Radioengineering, September 2010, vol. 19, no. 3, p. 378 – 385.
- SIPUS, Z., KILDAL, P.-S., LEIJON, R., JOHANSSON, M. An algorithm for calculating Green’s functions for planar, circular cylindrical and spherical multilayer substrates. Applied Computational Electromagnetics Society Journal, 1998, vol. 13, p. 243 – 254.
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Keywords: Radiation pattern, spherical array, sidelobe level reduction, uniform and nonuniform distribution of antenna elements

**Jing-jing Yang, Ming Huang, Cheng-fu Yang, Ji-hong Shi**
[references] [full-text]

Arbitrary Shape Electromagnetic Transparent Device Based on Laplace’s Equation

Transparent device is deliberately-designed electromagnetic structure that is transparent to electromagnetic wave. It can be used as a radome structure which is capable of protection antenna inside without sacrificing its performance. In this paper, two-dimensional (2D) arbitrary shape electromagnetic transparent device is designed based on transformation optics. Laplace’s equation is adopted to construct the coordinate mapping between the original space and the transformed space. The design method is flexibly extended to three-dimensional (3D) case, which greatly enhances the applicability of transparent device. The protection of a horn antenna is taken as an example to show the effectiveness of the transparent device. Since the performance of the transparent device is independent on the inner antenna, it can be designed separately. Full-wave simulations are made to validate the results.

- PENDRY, J. B., SCHURIG, D., SMITH, D. R. Controlling electromagnetic fields. Science, 2006, vol. 312, no.5781, p. 1780-1782.
- LEONHARDT, U. Optical conformal mapping. Science, 2006, vol. 312, no. 5781, p. 1777-1780.
- LEONHARDT, U. Metamaterials: Towards invisibility in the visible. Nature Materials, 2009, vol. 8, no. 7, p. 537-538.
- VALENTINE, J., LI, J., ZENTGRAF, T., BARTAL, G., ZHANG, X. An optical cloak made of dielectrics. Nature Materials, 2009, vol. 8, no.7, p. 568-571.
- YAN, M., RUAN, Z., QIU, M. Cylindrical invisibility cloak with simplified material parameters is inherently visible. Phys. Rev. Lett., 2007, vol. 99, no. 23, p. 233901.
- RAHM, M., SCHURIG, D., ROBERTS, D. A., CUMMER, S. A., SMITH, D. R., PENDRY, J. B. Design of electromagnetic cloaks and concentrators using form-invariant coordinate transformations of Maxwell’s equations. Photonics and Nanostructures- Fundamentals and Applications, 2008, vol. 6, no. 1, p. 87-95.
- YANG, J. J., HUANG, M., YANG, C. F., XIAO, Z., PENG, J. H. Metamaterial electromagnetic concentrators with arbitrary geometries. Optics Express, 2009, vol. 17, no. 22, p. 19656-19661.
- YU, G. X., CUI, T. J., JIANG, W. X. Design of transparent structure using metamaterial. J. Infrared Milli Terahz Waves, 2009, vol. 30, no. 6, p. 633-641.
- YANG, C. F., YANG, J. J., HUANG, M., SHI, J. H., PENG, J. H. Electromagnetic cylindrical transparent devices with irregular cross section. Radioengineering, 2010, vol. 19, no. 1, p. 136-140.
- MEI, Z. L., NIU, T. M., BAI, J., CUI, T. J. Design of transparent cloaks with arbitrarily inner and outer boundaries. Journal of Applied Physics, 2010, vol. 107, no. 12, p. 124908.
- RAHM, M., CUMMER, S. A., SCHURIG, D., PENDRY, J. B., SMITH, D. R. Optical design of reflectionless complex media by finite embedded coordinate transformations. Phys. Rev. Lett., 2008, vol. 100, no. 6, p. 063903.
- CHEN, H., CHAN, C. T. Transformation media that rotate electromagnetic fields. Appl. Phys. Lett., 2007, vol.90, no. 24, p. 241105.
- ROBERTS, D. A., RAHM, M., PENDRY, J. B., SMITH, D. R. Transformation-optical design of sharp waveguide bends and corners. Appl. Phys. Lett., 2008, vol. 93, no. 25, p. 251111.
- MA, H., QU, S., XU, Z., WANG, J. Numerical method for designing approximate cloaks with arbitrary shapes. Phys. Rev. E, 2008, vol. 78, no. 3, p. 036608.
- CHEN, X., FU, Y., YUAN, N. Invisible cloak design with controlled constitutive parameters and arbitrary shaped boundaries through Helmholtz’s equation. Optics Express, 2009, vol. 17, no. 5, p. 3581-3586.
- HU, J., ZHOU, X., HU, G. Design method for electromagnetic cloak with arbitrary shapes based on Laplace's equation. Optics Express, 2009, vol. 17, no. 5, p. 1308-1320.
- QIU, C. W., NOVITSKY, A., GAO, L. Inverse design mechanism of cylindrical cloaks without knowledge of the required coordinate transformation, J. Opt. Soc. Am. A, 2010, vol. 27, no. 5, p. 1079- 1082.
- SCHURIG, D., PENDRY, J. B., SMITH, D. R. Calculation of material properties and ray tracing in transformation media. Optics Express, 2006, vol. 14, no. 21, p. 9794.
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Keywords: Transparent device; metamaterials; coordinate transformation; finite element method

**He-Xiu Xu, Guang-Ming Wang, Jian-Gang Liang**
[references] [full-text]

Novel Designed CSRRs and Its Application in Tunable Tri-Band Bandpass Filter Based on Fractal Geometry

In this paper, we propose and research a novel miniaturized composite right/left handed transmission line (CRLH TL) cell based on revised complementary split ring resonators (CSRRs) for the first time. Novel CRLH TL cell is demonstrated with lower transmission and reflection zeros from electrical and electromagnetic (EM) simulation results. Negative refractive index of CRLH effect is successfully demonstrated by the revised NRW retrieval method. Then based on this, a tri-band bandpass filter (BPF) is synthesized and fabricated by using the proposed CRLH TL cell (providing the primary GSM band) and Koch fractal-shaped microstrip line (ML) (generating the upper GPS and ISM bands). Our recent work has also found that open-circuit stub embedded in Koch-shaped ML can be optimized to adjust the ratio of the upper two bands, thus afford us additional flexibility in BPF design. Consistent result obtained from simulation and measurement is presented which have verified the design concept.

- LIN, Y.-S., LIU, C.-C., LI, K.-M., CHEN, C.-H. Design of an LTCC tri-band transceiver module for GPRS mobile applications. IEEE Trans. Microw. Theory Tech., Dec. 2004, vol. 52, no. 12, p. 2718–2724.
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Keywords: Miniaturization, bandpass filter (BPF), composite right/left handed transmission line (CRLH TL), complementary split ring resonators (CSRRs), tri-band, fractals

**R. Sotner, J. Jerabek, R. Prokop, K. Vrba**
[references] [full-text]

Current Gain Controlled CCTA and its Application in Quadrature Oscillator and Direct Frequency Modulator

A modified conception of adjustable current conveyor transconductance amplifier (CCTA) and its interesting application in simple quadrature oscillator expandable for direct frequency modulation purposes, employing only four grounded passive elements is presented in this paper. It is quite simple solution for modern communication subsystem components. An electronic adjusting of the oscillation frequency is easily possible and control of condition of the oscillation is realized via only one grounded resistor. The characteristic equation, condition of oscillation and major parasitic influences of real active part are discussed. The verification includes PSpice simulation and measurement with the CCTA block formed by commercially available active elements.

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- LAHIRI, A. Explicit-current-output quadrature oscillator using second-generation current conveyor transconductance amplifier. Radioengineering, 2009, vol. 18, no. 4, p. 522-526.
- SIRIPRUCHYANUN, M., JAIKLA, W. Current controlled current conveyor transconductance amplifier (CCCCTA): a building block for analog signal processing. Electrical Engineering Springer, 2008, vol. 90, no. 6, p. 443-453.
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- JAIKLA, W., SIRIPRUCHYANUN, M., BAJER, J., BIOLEK, D. A simple current-mode quadrature oscillator using single CDTA. Radioengineering, 2008, vol. 17, no. 4, p. 33-40.
- BUMRONGHOKE, T., JAIKLA, W., SIRIPRUCHYANUN, M. An electronic controllable, simple current-mode oscillator using single MO-CCCCTA and grounded capacitors. In Proceedings of the 1st International Conference on Technical Education (ICTE2009). Thailand, 2010, p. 217-220.
- SOTNER, R., JERABEK, J., PETRZELA, J., DOSTAL, T., VRBA, K. Electronically tunable simple oscillator based on singleoutput and multiple-output transconductor. IEICE Electronics Express, 2009, vol. 6, no. 20, p. 1476-1482.
- HORNG, J., LEE, H., WU, J. Electronically tunable third-order quadrature oscillator using CDTAs. Radioengineering, 2010, vol. 19, no. 2, p. 326-330.
- SOTNER, R., HRUBOS, Z., SLEZAK, J., DOSTAL, T. Simply adjustable sinusoidal oscillator based on negative three-port current conveyors. Radioengineering, 2010, vol. 19, no. 3, p. 446 to 453.

Keywords: Electronic adjusting, quadrature oscillator, controllable active element, CCTA

**M. Kumngern, U. Torteanchai, K. Dejhan**
[references] [full-text]

Voltage-Controlled Floating Resistor Using DDCC

This paper presents a new simple configuration to realize the voltage-controlled floating resistor, which is suitable for integrated circuit implementation. The proposed resistor is composed of three main components: MOS transistor operating in the non-saturation region, DDCC, and MOS voltage divider. The MOS transistor operating in the non-saturation region is used to configure a floating linear resistor. The DDCC and the MOS transistor voltage divider are used for canceling the nonlinear component term of MOS transistor in the non-saturation region to obtain a linear current/voltage relationship. The DDCC is employed to provide a simple summer of the circuit. This circuit offers an ease for realizing the voltage divider circuit and the temperature effect that includes in term of threshold voltage can be compensated. The proposed configuration employs only 16 MOS transistors. The performances of the proposed circuit are simulated with PSPICE to confirm the presented theory.

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Keywords: Floating resistor, Voltage-controlled resistor, CMOS, Differential difference current conveyor (DDCC)

**V. Biolkova, J. Bajer, D. Biolek**
[references] [full-text]

Four-Phase Oscillators Employing Two Active Elements

Two novel four-phase voltage-output oscillators are proposed. These circuits can also be utilized as quadrature oscillators with floating outputs. Each oscillator employs two DO-CIBA (Differential Output- Current Inverter Buffered Amplifier), two grounded capacitors, and four or three resistors. Independent control of the oscillation frequency (OF) and oscillation condition is practicable in both oscillators. Real measurements on the oscillator specimens confirm the ability of easy OF control and extra low THD, which is less than 0.07%.

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- LAHIRI, A. New current-mode quadrature oscillators using CDTA. IEICE Electronics Express, 2009, vol. 6, no. 3, p. 135-140.
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- MAHESHWARI, S., KHAN, I. A. Current controlled third order quadrature oscillator. IEE Proc.-Circuits Devices Syst., 2005, vol. 152, no. 6, p. 605-607.
- HORNG, J. W., LEE, H., WU, J. Y. Electronically tunable thirdorder quadrature oscillator using CDTAs. Radioengineering, 2010, vol. 19, no.2, p. 326-330.
- TANGSRIRAT, W., PRASERTOSM, D., PIYATAT, T., SURAKAMPONTORN, W. Single-resistance-controlled quadrature oscillator using current differencing buffered amplifiers. Int. J. Electronics, 2008, vol. 95-11, p. 1119-1126.
- LAHIRI, A. Explicit-current-output quadrature oscillator using second-generation current conveyor transconductance amplifier. Radioengineering, 2009, vol. 18, p. 522-526.
- BAJER, J., BIOLEK, D. Digitally controlled quadrature oscillator employing two ZC-CG-CDBAs. In Proc. of Int. Conf. EDS-IMAPS 2009. Brno (Czech Republic), 2009, p. 298-303.
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- OP860. Wide Bandwidth Operational Transconductance Amplifier (OTA) and Buffer. Datasheet, Texas Instruments, SBOS331B, June 2006.
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Keywords: Four-phase oscillator, DO-CIBA

**P. Varshney, M. Gupta, G. S. Visweswaran**
[references] [full-text]

Switched Capacitor Realizations of Fractional-Order Differentiators and Integrators Based on an Operator with Improved Performance

In this paper, switched capacitor realizations of discretized models of half differentiator and half integrator based on a new operator with improved performance have been proposed. This Al-Hsue operator is the weighted sum of the Al-Alaoui operator and the Hsue operator. The discretized models of the Al-Hsue operator have been expanded using Taylor Series Expansion and Continued Fraction Expansion, to be able to develop the Switched Capacitor realizations. These Switched Capacitor realizations are implemented using Spice and the results obtained are compared with the theoretical results of the continuous- time domain half differentiators and integrators. These Spice simulation results are also compared with the results of existing Al-Alaoui operator and Hsue operator based Switched Capacitor realizations of half differentiators and integrators of order 1/2. The results validate the effectiveness of the Switched Capacitor circuit implementation of the proposed approach.

- PETRAS, I., PODLUBNY, I., O'LEARY, P., DORCAK L., VINAGRE, B. M. Analogue Realizations of Fractional Order Controllers. Faculty BERG, TU Kosice, p. 84, ISBN 80-7099-627- 7, 2002.
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Keywords: Half differentiator, half integrator, Al-Alaoui operator, Hsue operator, Al-Hsue operator

**A. Lahiri**
[references] [full-text]

Deriving (MO)(I)CCCII Based Second-order Sinusoidal Oscillators with Non-interactive Tuning Laws using State Variable Method

The paper discusses systematic realization of second-order sinusoidal oscillators using multiple-output second-generation current controlled conveyor (MO-CCCII) and/or its inverting equivalent, namely the multiple-output inverting second-generation current controlled conveyor (MO-ICCCII) by state variable method. State variable method is a powerful technique and has been used extensively in the past to realize active RC oscillators using a variety of active building blocks (ABB). In this work, a noninteractive relationship between the condition of oscillation (CO) and the frequency of oscillation (FO) has been chosen priori and then state variable method is applied to derive the oscillators with grounded capacitors. All the resulting oscillator circuits, eight of them, are “resistor-less”, employ grounded capacitors and do not use more than three (MO)(I)CCCIIs. PSPICE simulation results of a possible CMOS implementation of the oscillators using 0:35μm TSMC CMOS technology parameters have validated their workability.

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Keywords: Sinusoidal oscillators, multiple-output secondgeneration current controlled conveyor (MO-CCCII), multiple-output second-generation inverting current controlled conveyor (MO-ICCCII), state variable method

**D. Prasad, D. R. Bhaskar, A. K. Singh**
[references] [full-text]

Electronically Controllable Grounded Capacitor Current-Mode Quadrature Oscillator using single MO-CCCDTA

This paper presents an electronically controllable grounded capacitor quadrature oscillator using single multiple-output current controlled current differencing transconductance amplifier (MO-CCCDTA) as an active element. The proposed circuit employs a single MOCCCDTA, two grounded capacitors and one grounded resistor and offers the advantages of (i) independent control of condition of oscillation (CO) and frequency of oscillation (FO), and (ii) low active and passive sensitivities. The workability of proposed configuration has been demonstrated by PSPICE simulation.

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Keywords: MO-CCCDTA, quadrature oscillator, current-mode circuits.

**C. Wang, G. Peng, M. Ma, Z. Li**
[references] [full-text]

A New Low-Power CMOS Quadrature VCO with Current Reused Structure

A new quadrature voltage controlled oscillator (QVCO) circuit topology is proposed for low-voltage and low-power applications. In the proposed circuit, two oscillators with current-reused structure are coupled to each other by two P&N-MOS pairs. In this way, low phase noise quadrature signals are generated with low-voltage and low-power. The simulation is made by Cadence in chartered 0.18 μm CMOS process. The simulation result shows that the QVCO phase noise is approximately - 117.1 dBc/Hz at 1MHz offset from 1.8 GHz operation frequency. The QVCO dissipates 1.92 mW with a 1.1 V supply voltage.

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Keywords: Coupling, P&N-MOS pair, VCO, Low-power, Lowvoltage, Phase noise, Oscillator, Quadrature

**K. Molnar, N. Herencsar**
[full-text]

Guest Editorial: Special Issue on Signal Processing – Selected Papers from the TSP 2010 Conference

**J. Haze**
[full-text]

Guest Editorial IMAPS Electronic Devices and Systems International Conference, 2010