Wideband HF signals dispersion distortion compensator based on digital filter banks. Theory and approbation

Abstract

The article proposes a computationally effective scheme of the dispersion distortions compensation device, based on the modification of the classical 2M-channel digital filter banks. The main idea of dispersion compensation is equalization of the delay and elimination of the phase shift, because the frequency dispersion of the signal is the delay of the signal at each frequency and the phase shift. The dispersion distortions compensation device involves the set of FIR filters and the delay line. The set of FIR filters eliminate fractional delay are implemented in the compensation scheme by means of the signal re-digitization with the help of the 19-th degree interpolation polynomial. Each of the FIR filters is multiplied by a coefficient that eliminates the certain phase shift. The delay line eliminates the integer part of the delay. Also, this article estimates the required number of channels in a dispersion compensation device based on a bank of digital filters and compares compensation algorithms on the basis of a filter bank and a filter-compensator. Analytical expressions are obtained for the approximate calculation of the maximum and standard deviations of the phase response of the system, reflecting the dependence of the phase response on the number of frequency subchannels, the order of the interpolation polynomial of the interpolator, the length of the polyphase components of the prototype filter, the slope of the dispersion characteristic, and the passband of the filter bank. Besides, a theoretical and experimental study is concluded, the purpose of which is to confirm the performance and efficiency (availability in terms of the signal-to-noise ratio) of the algorithms for compensating for dispersion distortion of broadband signals in the decameter band, embedded in a digital analysissynthesis filter bank.