FM and PM signal carrier capturing method applicable to random modulation degree

Abstract

The invention provides an FM and PM signal carrier capturing method applicable to a random modulation degree. The method comprises following steps of firstly, carrying out down-sampling filtering to input digital baseband signals, thus obtaining down-sampled digital baseband signals; then respectively mixing the digital baseband signals with multiple groups of set local carriers, thus realizing frequency spectrum shift of the baseband signals; carrying out FFT conversion to each frequency spectrum shift branch signal; calculating the power of each spectrum line; searching spectrum line peak values region by region; storing searching results; after a plurality of times of searching is finished, carrying out frequency point verification; eliminating noise interferences, thus obtaining true signal spectrum lines; finally carrying out symmetry judgment to the obtained true signal spectrum lines, thus determining a capturing result. According to the method, the frequency resolution is improved through the frequency spectrum shift; the peak values are searched region by region in the whole capturing range according to the frequencies; the true signals are counted through many times of capturing; the weak signals can be searched in a low signal to noise ratio environment; and the method is applicable to FM and PM signal carrier capturing of random modulation degree.

Description

technical field [0001] The invention relates to the technical field of carrier acquisition of a measurement and control system, in particular to an FM and PM signal carrier acquisition method applicable to any modulation degree. Background technique [0002] In the whole star test, the Cortex baseband processor is usually used to complete the reception and demodulation of satellite telemetry signals and ranging signals. In the actual test process, the stability of the Cortex is not satisfactory, and problems such as failure to start normally and abnormal open-loop self-calibration often occur, and the measurement data is inaccurate after a long time of starting up, and it needs to be turned off for cooling, which greatly affects the The automation level of the test reduces the test efficiency and affects the progress of the whole star test; on the other hand, Cortex is expensive, which is not conducive to the cost control of ground equipment. Therefore, there is an urgent n...

AI Technical Summary

Problems solved by technology

In order to restore the original signal, the receiver needs to perform carrier capture on the received signal. The traditional FFT capture algorithm is affected by the modulation index of phase modulation or frequency modulation. When the modulation index is large, the power of the main carrier in the spectrum of the received signal is lower than that of the subcarrier. At this time, the traditional method determines the carrier frequency by searching the peak of the spectrum, which will lead to false capture of the carrier.

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