# April 1998, Volume 7, Number 1

**T. Dostal**
[full-text]

High Frequency State-Variable Biquadratic Active Filters

The state-variable (KHN) active RC biquadratic filters with good performance in high frequency range , flexibility of outputs (LP, HP, BP), low sensitivities in novel current and hybrid modes, using current conveyors, transimpedance, trans-admittance and current operational amplifiers, are given in this paper.

**R. Kucera, J. Vlcek, K. Vlcek**
[full-text]

DSP Implementation of Image Compression by Multiresolutional Analysis

Wavelet algorithms allow considerably higher compression rates compared to Fourier transform based methods. The most important field of applications of wavelet transforms is that the image is captured in few wavelet coefficients. The successful applications in compression of image or in series of images in both the space and the time dimensions. Compression algorithms exploit the multi-scale nature of the wavelet transform.

**P. Vorel**
[full-text]

Kvasiresonant DC-DC Converter with Switching at Zero Current - Part 1

A kvasiresonant DC - DC converter and its control circuits are proposed. The relations useful for design of the converter will be deduced in the part 2.

The fundamental idea of the converter is the switching -on and -off a transistor at zero current. In this way the switching losses are eliminated. It enables to design a converter with a large output power (several kW), high switching frequency (about 200 kHz), very good efficiency and low radiation.

**P. Horsky**
[full-text]

Standards of Distorted Signal for Calibration of Total Harmonic Distortion Meters

In this article a survey and evaluation of some progressive approaches to the standards of non-linear distortion is reported. Some types of standards of signals with the known total harmonic distortion used for calibration of distortion measuring instruments are proposed. This article is based on our previous work directed at the development of a multifunctional THD standard which is now used in the Czech Metrological Institute.

**V. Georgiev**
[full-text]

Some Applied Aspects of Rational Higher-Order s-z Transformations

Some contributions of higher-order s-z transforms are exposed related with the conversion of a continuous-time transfer function into its discrete-time counterpart. The developed algorithm of sensitivity analysis with respect to mapping parameters, prototype coefficients and sampling rate combined with numerical experiments can be efficiently use to motivate the selection of s-z transform and thereby to provide a suitable basis for an optimal solution of a general design problem.