Signal model based on Maxwell's equations

High resolution imaging is an important trend for SAR. The wide bandwidth signal is a must for high resolution. The error of traditional model based on the narrow bandwidth system may be inevitable for high resolution imaging. In this paper, a general SAR echo model is derived for the wide bandwidth system, and we also get the error factor between the traditional and general model. By simulating the two models, the conclusion is derived that if the transmitted signal is LFM waveform, the target is single and the receiving antenna is unit weight, the error of the two models can be neglected. The general echo model in more complicated situations is in the ongoing research. This study will make for the further research of high resolution SAR imaging algorithm.