К.Yu. Lozhkin, S.S. Prozhetorko    

MESC AF «N.E. Zhukovsky and Y.A. Gagarin Air Force Academy» (Voronezh, Russia)

In modern communication systems of various wavelengths, signals with amplitude-phase modulation are widely used, including multiposition signals with quadrature amplitude modulation with a rectangular signal constellation. However, studies of the synthesis and evaluation of the noise immunity of receiving these signals published in Russian and foreign literature under conditions of the effects of station or intentional signal-like jamming of various structures are not complete enough, since they do not allow a strict description of the structure of the most unfavorable interference on the reception interval of not one, but the premises multi-position signal with quadrature amplitude modulation. On the basis of mathematical apparatus of indicators of events the generalized expression of average probability of the correct reception of sequence from m elements not fading signal with quadrature amplitude modulation in the form of a functional from a interference of the arbitrary structure is received. With application of calculus of variations by criterion in the form of a minimum of average probability of the correct reception of sequence from m elements of a considered signal the most unfavorable interference to the correlative receiving-solving device of this signal is synthesized at restriction on average power of a interference. On an indicator in the form of average probability of the correct reception of sequence from m elements signal with quadrature amplitude modulation the estimation of interference immunity of its reception in the conditions of influence synthesized, harmonic, PSK and APSK interference is fulfilled. It is shown that the dependences of the probability of the correct reception of a sequence of m packets of a multi-position signal with quadrature amplitude modulation on the signal-to-jamming ratio with respect to effective voltages under the influence of the considered interference are characterized by a threshold effect. It was found that m = 1 the noise immunity of receiving a multi-position signal with quadrature amplitude modulation under the conditions of harmonic jamming without frequency detuning or synthesized noise is the same, because in this case the structures of these interference coincide. The noise immunity of signal reception under conditions of exposure to an asynchronous PSK jamming is higher compared to synthesized and harmonic jamming due to the lack of synchronization of the clock moments of PSK jamming and the signal at the input of the decision-making device. The greatest noise immunity of the considered signal is observed under the influence of synchronous APSK jamming. It was determined that m > 1 the most unfavorable of the considered interference is the synthesized jamming. Further, as the noise immunity of receiving a multi-position signal with quadrature amplitude modulation increases, harmonic jamming without frequency detuning follows, followed by an asynchronous PSK jamming. The greatest noise immunity of signal reception is ensured under the influence of APSK jamming, which is caused by an unstable amplitude level of interfering bursts.It is shown that with increasing noise immunity of receiving a multi-position signal with quadrature amplitude modulation under the influence of APSK jamming, PSK jamming and synthesized jamming it turns out to be comparable.

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