Abstract: Azimuth displaced phase center antenna (DPCA) multi-channel technique can improve the azimuth resolution of spaceborne TOPSAR (Terrain Observation by Progressive Scans) mode, but Doppler spectrum aliasing of TOPSAR imaging scene and azimuth non-uniform sampling lead to multi-channel TOPSAR imaging hard to be implemented. As for this question, a new imaging approach for spaceborne multi-channel TOPSAR data is proposed. This approach adaptively shifts azimuth transmit/receive antenna phase center in order to yield uniformly spaced samples and resolves TOPSAR Doppler spectrum aliasing problem by the azimuth mosaicking approach. Finally, the modified SPECAN (spectrum analysis) imaging algorithm is introduced to focus residual raw data. This imaging approach avoids azimuth multi-channel non-uniform signal reconstruction; the mosaicking approach and modified SPECAN imaging approach are introduced to avoid azimuth data block division and azimuth time domain extension. The imaging results of point and distrusted targets validate the presented imaging approach.

Key words: Terrain Observation by ProGressive Scans(TOPSAR), Displaced Phase Center Antenna (DPCA), Aliasing, Spectrum Analysis(SPECAN), Chirp-z Transform