摘要： Phase di?erence measurement of sinusoidal signals can be used for phase error calibration of the spaceborne single-pass interferometric synthetic aperture radar (InSAR) system. However, there are currently very few papers devoted to the discussion of phase di?erence measurement of high-frequency internal calibration signals of the InSAR system, especially the discussion of sampling frequency selection and the corresponding measuring method when the high-frequency signals are sampled under the under-sampling condition. To solve this problem, a phase di?erence measurement method for high-frequency sinusoidal signals is proposed, and the corresponding sampling frequency selection criteria under the under-sampling condition is determined. First, according to the selection criteria, the appropriate under-sampling frequency was chosen to sample the two sinusoidal signals with the same frequency. Then, the sampled signals were ?ltered by limited recursive average ?ltering (LRAF) and coherently accumulated in the cycle of the baseband signal. Third, the ?ltered and accumulated signals were used to calculate the phase di?erence of the two sinusoidal signals using the discrete Fourier transform (DFT), digital correlation (DC), and Hilbert transform (HT)-based methods. Lastly, the measurement accuracy of the three methods were compared respectively by di?erent simulation experiments. Theoretical analysis and experiments veri?ed the e?ectiveness of the proposed method for the phase error calibration of the InSAR system.