Method of High Signal-to-Noise Ratio and Wide Swath SAR Imaging Based on Continuous Pulse Coding

In synthetic aperture radar (SAR), increasing the pulsewidth of signal is an effective way to achieve high signal-to-noise ratio (HSNR) imaging. However, when the pulse repetition frequency (PRF) is fixed, increasing the pulsewidth will reduce the maximum unambiguous swath width of SAR. In order to solve this contradiction, a method based on continuous pulse coding (CPC) which increases the average transmit power by multiple pulses with varying high PRF is proposed in this article. Due to the small interval between pulses, the echo will have range ambiguity and occlusion problems. To obtain the complete echo, we first use the form of CPC signal and the swath width of radar to construct a linear equation set to model the ambiguous echo of each receiving window. Next, the established linear equations are split according to the distribution law of receiving window. Finally, the echo energy accumulation of multiple pulses is accomplished by solving the split sublinear equations. Therefore, the echo with both swath width corresponding to narrow pulse and HSNR corresponding to wide pulse is obtained to realize HSNR and wide swath SAR imaging. The experimental results have confirmed the effectiveness of the method proposed in this article.