Nonlinear Error Compensation of PGC Demodulation With the Calculation of Carrier Phase Delay and Phase Modulation Depth

We propose a novel phase generated carrier (PGC) demodulation method by simultaneously calculating the carrier phase delay (θ) and the phase modulation depth (m) to compensate the nonlinear error introduced by θ and m. Firstly, θ is calculated by adopting the fundamental in-phase and quadrature harmonic components and their differential components. Secondly, this calculated θ is used to set the phases of the harmonic components of reference carrier signal to obtain three new harmonic components independent of θ. Later, m is calculated and compensated by adopting the three new harmonic components and their differential components to obtain the demodulated result. Theoretical analysis and realization of the method are described in detail. Simulation and displacement measurement experiments with different θ and m are carried out to validate the proposed method. The experimental results demonstrate that the proposed method can accurately calculate and compensate θ and m, and effectively eliminate the nonlinear error of the demodulated signal.