V.A. Simongauz – Ph. D. (Eng.), Associate Professor, Department 402, Moscow Aviation Institute (National Research University)
In practice often the task of synchronization at the reception of radio signal with binary phase manipulation decides consistently. In phase synchronization is the beginning provided, and then symbol. For phase synchronization use the known the Costas loop. This circuit provides reliable track after a carrier phase only in the case when relation of power of signal toward power of noise on her entrance is large enough (no less than ~10 дБ). With reduction of relation signal/noise on an entrance power losses increase. Steady work of circuit is violated, when relation signal/noise arrives at a threshold value. There is suppression of the weak signal due to noise.
In the article the task of construction of the system of joint phase and symbol synchronization is examined on the basis of maximum likelihood method. Thus a function of likelihood is from the functional of two-dimensional density of probability for components of complex envelope of entrance process. Correlations, qualificatory the estimations of maximal likelihood for the phase of carrier and delay of modulating signal used for a construction of tracker algorithms.
Unlike the widely used methods on the basis of the Costas loop, the considered algorithms provide reliable track after parameters at the small values of power relation without suppression of the weak signal due to noise, that it is especially important for a deep-space communication.
Power losses in the distinguished symbols depend only on errors tracks the possible level of that can be provided by the choice of band of loop of phase track and band of band of delay track. The ratios defining the power relation in a band of a symbol, the ratios defining bands of the tracking systems and dispersion of errors of tracking are presented.