METHOD OF INCREASING INFORMATION SECURITY IN COMMUNICATION CHANNELS USING MICROWAVE FILTERS WITH ATTENUATION POLES AT PREDETERMINED FREQUENCIES

Abstract

The article presents a review of studies devoted to the consideration of modern methods of organising the transmission of critical information. The task of protecting information in microwave communication channels is inextricably linked to the problems of electronic compatibility and electronic countermeasures. Microwave filters are an integral part of radio engineering and telecommunication systems, performing frequency selection of signals, suppression of interference, and decoupling of receiving and transmitting paths. Therefore, the improvement of traditional and development of new methods for designing microwave filters in order to improve their functional and mass-dimensional characteristics is an urgent task. The aim of this article is to develop a method for the direct synthesis of stub quasi-elliptical filters with an equal-wave response in the passband and transmission zeros at specified frequencies in the blocking band. The presented method and the proposed relations can serve as a basis for developing a procedure for synthesising bandpass quasi-elliptic loop filters, as well as low-pass filters and bandpass filters implemented on segments of coupled lines. An analysis of the use of two-sectional loops to create zeroes of the filter’s transmission coefficient at given frequencies and the use of Chebyshev functions and algebraic Chebyshev-Markov cosine fractions to approximate its frequency response is carried out A new method for the direct synthesis of quasi-elliptic low-pass filters has been developed, which provides optimal characteristics that fully meet the potential capabilities of filter structures in terms of frequency selectivity. The presented method and the proposed relations can serve as a basis for developing a procedure for synthesising bandpass quasi-elliptic stub filters, as well as low-pass filters and bandpass filters implemented on segments of coupled lines. For stub quasi-elliptic low-pass filters, without the use of prototype filters. The filtering functions for the filter structures composed of single-section and two-section stubs are determined. On the basis of Chebyshev functions and the algebraic Chebyshev-Markov cosine fraction, functions that approximate the filtering functions of the filters are compiled. The methodology for implementing filters and the relations that determine the scattering parameters of filter elements are proposed. The filtering functions and approximation functions for a number of filter structures are compiled. The relations used in the selection of elements from the overall filter structure at the implementation stage are determined. The scientific novelty of the work lies in the development of a new method for synthesising quasi-elliptic low-pass loop filters, which ensures the realisation of optimal amplitude-frequency characteristics due to the full use of the potential capabilities of the synthesised filter structures in terms of frequency selectivity.