One of the radiomonitoring stages of complex phase-shifted signals, used in satellite navigation systems are estimation and measurement of the carrier frequency, measurement of Doppler shift and it changes in a time. Since the experimental phase-shift keyed signals with radiomonitoring are unknown form, then the solution of the exact frequency estimation is expedient to perform with the use of quasi-algorithms based on autocorrelation processing.
In constructing the autocorrelation of the frequency discriminator, which provides evaluation of the Doppler frequency shift phase-shift keyed signals in the operation of satellite navigation systems in "normal" mode, when the a priori known to the average frequency of the radiation , the duration of the element , a code interval , a bit interval , and manipulating the pseudorandom sequence used fixed dispersionless delay lines.
In the operation of satellite navigation systems in the "abnormal" mode, when a priori information on the above parameters of phase-shifted signals is absent, the implementation of the autocorrelation of the frequency discriminator, causes difficulties due to the need to implement a highly stable tunable delay lines with a bandwidth of 20 MHz, step changes and delays in the range of variation with delays of up to based on analog components.
To overcome this problem should be used in the autocorrelation frequency discriminator direct conversion of radio signals in the region of zero frequency in the quadrature channels with the subsequent realization of a tunable delay line based on digital components.
In this paper we investigate the principles of adaptive autocorrelation frequency discriminator with the direct conversion of signals in the quadrature channels, intended for radio monitoring of complex quasi-phase-shift keyed signals with an unknown form, describes methods for analyzing the basic characteristics of the radiomonitoring subsystem.
It is shown that the transition to measure the frequency of phase manipulated signal to the second "lobe" of the autocorrelation function, adaptive autocorrelation frequency discriminator provides a significant gain in accuracy of estimating the frequency of phase-shifted signals, which allows to estimate the Doppler increment of an input signal to noise ratio is much smaller than unity as in "normal" and "abnormal" mode of operation of satellite navigation systems of communication.