High resolution for software-defined GPS-based SAR imaging using waveform-modulated range-compressed pulse: field experimental demonstration

This paper presents an experimental demonstration with respect to a high-range-resolution imaging scheme for software-defined receiver-based passive GPS-based SAR, and a signal processing scheme for imaging is proposed correspondingly. In the proposed scheme, to reduce the computational complexity and high-memory requirement for receiver, GPS signals are down-converted to baseband for digitized collection at first. After performing range compression, the region of interest is selected based on the numbers of detected compressed pulses. Thereafter, the detected compressed pulses are up-sampled, modulated by a waveform with the frequency larger than bandwidth value and then spectrum-equalized for obtaining high-resolution range-compressed signals. The field results obtained from both land and ocean scenarios indicate that compared to the conventional signal processing scheme for imaging, indeed the proposed scheme can provide a significantly lower range ambiguity around the scene center; compared with the authors' previous related work (Zheng et al. in Sensors, 2017. 10.3390/s17071496), the proposed scheme is obviously more computationally efficient.