A Range Ambiguity Resolution Approach for High-Resolution and Wide-Swath SAR Imaging Using Frequency Diverse Array

In spaceborne synthetic aperture radar (SAR), it is a challenging problem to realize high resolution and wide swath imaging (HRWS) due to the conflict between Doppler and range ambiguities. To mitigate this conflict, a range ambiguity resolution approach for HRWS SAR imaging using frequency diverse array (FDA) is proposed in this paper. The FDA employs a set of slightly different carrier frequencies, each of which is emitted by an individual array element. Frequency diversity introduces wave-path difference among the array elements, thus resulting in the range-angle-dependent property of transmit steering vector. Utilizing the extra degrees-of-freedom in range domain, FDA is capable of distinguishing the range ambiguous echoes in the spatial frequency domain. In our approach, the range ambiguous echoes are compensated by range dependence compensation (RDC) technique in the transmit spatial frequency domain. In the sequel, the range ambiguous echoes are separated by using a series of transmit beamformers as the echoes from different range regions are discriminable. Finally, traditional imaging processing is performed on the reconstructed unambiguous data to achieve HRWS imaging. Simulation results have verified the effectiveness of the proposed approach.