A.N. Lutkov - Head of Sector, JSC «Almaz-Antey». E-mail: anlutkov@gmail.ru

We consider discrete messages - transmission system (DMTS) based on radar. The system has the following particularities. Frame synchronization is performed by means of radar marker at the beginning of the message. Message transmission is carried out in an intermittent duty. Differential Binary Phase Shift Keying is used as the carrier modulation method. Quadrature signal processing is made in the demodulator. Transmission goes at the big speed between transmitter and receiver. Reliability of an information transmission has the highest priority. The boundary conditions of the symbol duration are set. The lower bound of the duration is defined from a condition of absence of an intersymbolical interference because of pass-band restrictions. The upper bound of the duration is defined proceeding from the admissible message transmission time. Estimation of losses in signal-to-noise ratio because of frame synchronization error and frequency displacement is performed. Expression for superposition of losses in signal-to-noise ratio from the specified factors is derived. The frame synchronization error which is caused by a radar error on range and the frequency displacement which is caused by carrier oscillator instability and Doppler Effect are considered. Analytical expression for optimal symbol duration is derived. Optimal symbol duration depends from restrictions on the accuracy of frame synchronization, on the accuracy of the frequency drift compensation method, pass-band and maximum admissible message transmission time in this expression. Application in the system of symbols of optimum duration increases the reliability of information transmission of DMTS due to minimization of losses in signal-to-noise ratio.

 

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