Modified adaptive filter for digital subdivision of a four-frequency differential laser gyro

This study represents a modified adaptive filter to suppress the beat noise of four-frequency differential laser gyro (FFDLG), which greatly affects the result of the eightfold digital subdivision. By constructing the demodulated signal model of FFDLG, the influence of beat noise to digital subdivision is analyzed. Based on the least mean square adaptive algorithm, a process of signal reconstruction and dead-zone operator of error are adopted in the modified adaptive algorithm. When implemented on a field-programmable gate array chip, the filter replaces the multiplication with 2:1 multiplexer to reduce the complexity of algorithm and resources in circuit. This circuit effectively suppresses the beat noise of the demodulated signal without changing the optical structure of the FFDLG and increases the signal-to-noise ratio from 20 dB to about 40 dB, which is conducive to improving the performance of the FFDLG.