Phase difference measurement of undersampled sinusoidal signals based on coherent accumulation and DFT

Phase difference measurement of sinusoidal signals can be used for phase calibration in spaceborne/airborne single-pass InSAR system. However, there are little discussions about the selection of the sampling frequency on the undersampling condition and corresponding measuring method when the signal's frequency is too high. In order to solve the problem aforementioned, this paper proposes a modified method based on Coherent Accumulation and DFT. Firstly, the appropriate under-sampling frequency is chosen to sample the two sinusoidal signals with the same frequency. Then, the sampled signals are coherent accumulated with the period of the baseband signal. Thirdly, the accumulated sampled signals are used to calculate the initial phases of the two sinusoidal signals by using the Discrete Fourier Transformation. Lastly, the phase difference is gotten from the initial phases. Experiment results prove the effectiveness of the method.