Synthesis Based On Broadband High-resolution Sar Technology

Synthetic aperture radar (SAR) is a kind of microwave imaging radar with high resolution, working under all weather, day and night conditions,which can also penetrate the ground and the vegetation. So it is applied to military field and civil field extensively. It is always a very important goal to obtain high resolution in the SAR development.Range resolution is determined by the bandwidth of the chirp signal. It brings about a lot of problems to increase the bandwidth while bandwidth synthesis is an efficient method to solve it. The subject of this article is to study the high resolution SAR system based on bandwidth synthesis and it can be divided into three parts as following.1. The features of high resolution SAR with bandwidth synthesis are analyzed first, including the imaging theory. Then the signal processing flow is presented for high resolution with bandwidth synthesis. It can be concluded that the differences between bandwidth synthesis signal and the ideal broad bandwidth signal transmitted and received directly are the synthesis process before imaging and the errors in every narrow bandwidth echo signal.2. Bandwidth synthesis can be divided by the echo division modality into the synthesis of sub-band received signals and the synthesis of stepped frequency signals. Besides, either of them has several methods. The approach analyzed in this article for sub-band signals is synthesis before imaging while the approach for stepped frequency signals can be divided into time domain synthesis, frequency domain synthesis and complex image domain synthesis. They are all proved by computer simulation after theoretical analysis and derivation.3. The error in SAR echo signal can result from radar system error; space spread error; motion error and target model error. The error forms and the error compensation process in stepped frequency signals are studied in detail. Then the error effect is presented by computer simulation. At last, the error calibration of the stepped signal is analyzed and a pulse signal experiment is implemented, which validates the compensation method and proves that the distortion of the pulse compression caused by phase errors between different stepped signals is much more seriousIt can be concluded from the synthesis method and error analysis that bandwidth synthesis is flexible to manage extremely broad bandwidth and efficient to increase the range resolution.