Noise Immunity Analysis of Coherent Demodulation of Synchronous Mutually non-Orthogonal Digital Signals with Minimum-Shift Keying

Abstract

Introduction. With the provision of the necessary level of economic and defense potential of the state, the problem of protection of lines and networks of digital radio is of high importance. There is a need among the set of technical methods to combat the obstacles to choose their rational set, which will ensure the implementation of modern requirements for noise immunity of digital radio links. The purpose of the study and  the basis of the article is to analyze the protection of coherent demodulation of a useful digital signals with frequency minimum-shift keying (MSK) under conditions of strong powerful obstacle. Theoretical results. In order to achieve this goal, a number of partial tasks were solved in the article, namely: a functional diagram of a coherent demodulator of synchronous mutually nonorthogonal digital signals with MSK was synthesized; the simulation model of the digital radio line, which operates under the conditions of a powerful MSK-obstacle, is developed, with the implementation on the receiving side of the functional scheme of the coherent demodulator of synchronous mutually nonorthogonal digital signals with MSK; a series of experiments were conducted for a number of signal-to-noise ratios and signal-to-obstacle in the communication channel; the analysis of the interference protection were conducted of coherent reception of a useful digital signals with MSK in conditions of synchronous  strong powerful obstacle. Conclusions. In the absence of MSK-obstacle the coherent demodulator of synchronous mutually nonorthogonal digital signals with MSK degenerates into a classical coherent demodulator of MSK-signal. The analysis reception protection of the MSK-signal under conditions of the influence of a powerful MSK-obstacle has shown that in case of exceeding the instantaneous power of MSK-obstacle, more than 7 dB over the instantaneous power of a useful signal, the negative influence on the noise immunity of receiving the latter is close to zero, and the noise immunity of reception is approaching of the coherent reception of the frequency-shift keying signal.