Realization of high stability PGC-EKF demodulation algorithm based on FPGA

In the phase generation carrier (PGC) arctan demodulation schemes, carrier phase delay (CPD) and phase modulation depth (C) fluctuation might lead to incorrect demodulated results. This paper realizes a high-stability PGC-extended Kalman filter (EKF) demodulation algorithm based on a Field-Programmable Gate Array (FPGA). EKF-based ellipse fitting algorithm is used to eliminate nonlinear errors in the two original quadrature signals. The function and logic correctness of the design are verified by simulation. The simulation results show that the algorithm can calculate the ellipse parameters accurately and quickly. In experimental comparisons with the traditional PGC-Arctan demodulation algorithm, the PGC-EKF algorithm demonstrates significant suppression of nonlinear distortion in the demodulated results. As C varies from 1.5rad to 3.5rad, the algorithm achieves a mean SINAD of 38.457 dB with a standard deviation of 0.312 dB. Similarly, as the CPD varies from 0 to , the mean SINAD remains at 38.033 dB with a standard deviation of 0.777 dB. In addition, the PGC-EKF algorithm exhibits high stability during long-term operation on FPGA boards. This is evidenced by the significantly lower SINAD standard deviation (1.319dB) compared to the PGC-Arctan algorithm (3.296dB) when C is 2.63rad and CPD is 0 degrees. The proposed PGC-EKF demodulation algorithm based on FPGA has broad application prospects in fiber optic interferometric sensors.