ISAR imaging for low earth-orbit target based on time-frequency-rate representation with cross-term suppression

Inverse synthetic aperture radar has been widely used in the imaging of space targets. The low earth-orbit target tends to introduce a time-variant Doppler shift in radar echo and the range-Doppler algorithm may fail in generating a focused image. In this paper, novel range-instantaneous-Doppler and range-instantaneous-chirp-rate methods are proposed based on the smoothed integrated high-resolution time-frequency-rate representation (SIHR-TFRR). The radar echo from one range cell is characterized as a multicomponent polynomial phase signal. The coefficients of the polynomial phase are estimated by the SIHR-TFRR algorithm. The effectiveness of the proposed methods are validated using the real-data experiments. Comparisons with the other methods are also provided.