Abstract: The confliction between swath width and resolution in the routine space-borne synthetic aperture radar (SAR) can be solved by displaced phase centers multi-beam in azimuth (DPCA) with ScanSAR in across-track direction. However, the pulse repetition frequency, sensor velocity and antenna size underlie a stringent timing requirement and any deviation will result in a non-uniform sampling in space domain. The paper derives an innovative frequency-domain reconstruction algorithm, which enables a recovery of the unambiguous Doppler spectrum also in case of a non-uniform sampling. This algorithm is not iterative and precise, and can improve greatly the flexibility of system and parameters choice. The simulation results which illustrate the algorithms validity show that the spurious image from the non-uniform sampling is suppressed to below -60 dB and the azimuth-ambiguity-to-signal ratio (AASR) is below -23 dB.