ПОДХОД К ИСПОЛЬЗОВАНИЮ ШИРОКОПОЛОСНЫХ СИГНАЛОВ В РАДИОТЕХНИЧЕСКИХ СИСТЕМАХ КВ-ДИАПАЗОНА С УЧЁТОМ ВЛИЯНИЯ ЧАСТОТНОЙ ДИСПЕРСИИ ИОНОСФЕРЫ
Authors: Иванов Д.В. , Рябова М.И. 
Published: February 2025

В работе с общих позиций рассмотрены подходы к использованию широкополосных сигналов в радиотехнических системах КВдиапазона. Показано, что при приёме для систем связи необходима фильтрация спектра носителя и частотной характеристики КВканала, для систем локации и зондирования спектра носителя, амплитуднофазовой дисперсии частотной характеристики. Представлено последовательное обоснование эффективности расширения полосы частот носителя для систем связи. Описаны модели эффектов потерь в энергетике этих сигналов изза нелинейной фазовой дисперсии частотной характеристики и обоснован метод её фильтрации при приёме широкополосных КВсигналов. Эффекты амплитуднофазовой дисперсии оценены в натурных экспериментах на радиолинии дальней связи (2600 км).

Introduction. One of the current problems of HF communication is the development of systems that employ radio signals with bandwidth of roughly 10 of the channel midband frequency. The usage of such signals is significantly restricted by the varying frequency dispersion in a radio channel. According to DARPA they are classified as wideband. Fast frequencyhopping spread spectrum (FHSS) signals are the most prospective for civilian and military users. The aim of the research is to develop a theory and carry out studies into the frequency dispersion of delay of signal of HF communication system. Besides, the specific topic of the research is the method of frequency dispersion correction for signals with fast FHSS. Findings. Paper is addressed to the problems of propagation of HF communication signals across the ionosphere. It was shown that the most negative effects occur when carrier signals are wideband and channel dispersion influences carrier modulation. The variations of the channel parameters over slow time complicate the problem of filtering. This rises the necessity in the development of adaptive filters that are matched to the channel frequency response. There are presented the methods for increasing guard ratio in spreading the bandwidth of a communication signal. It was proved that spectrum whitening is an effective method for suppression of interferences and fluctuation noise. The algorithm of spectrum spreading by means of fast frequency hopping is described. The fast FHSS advantage is that the signal has a low spectral density that improves the stealthiness of a communication system. However, in the HF band, frequency dispersion, multipath propagation and interference of magnetoionic components limit significant signal bandwidth spreading. The obliqueincidence sounding method is presented to study the frequency dependences of the signals group delay. It results in the intersymbol interference of chips because they are generated on different carriers and have different delays with respect to the transmitted chips due to the dispersion. We derived an expression for the maximum value of the phase jitter of the FHSS signal in the channel with dispersion. Additionally, we thoroughly studied an equalization method for overcoming the frequency dispersion of the delay of fast FHSS signal.