Spaceborne SAR echo signal simulation and target detection method

Comparing with the traditional passive optical remote sensing method,SAR(Synthetic Aperture Radar) has some unique advantages in many respects as anactive remote sensing equipment. Because traditional optical remote sensing methodworks in a passive way, which relies on observing the reflection of light, so it can onlywork when there are no obstruction, which greatly limits the observation time andrange. On the other hand, SAR works in an active way. By the means of emittingelectromagnetic waves to the destination area, SAR systems receive the reflectionelectromagnetic waves from these areas, and then using2D methods to process theseechoes to get an image which has different shading. As the electromagnetic wave has abetter ability of penetrating clouds than optical, so the SAR systems can observe theearth day and night and whole weather.Usually there will be a high cost to establish a real SAR system. Beforeestablishing the system, we should simulate the system first, and test whether theparameters of the system design is reasonable, the signal processing method is valid,the imaging result is satisfactory and so on. So how to find a proper way to simulatethe SAR system is still a focus nowadays.This dissertation conducts a study to the problems in SAR system simulation,which refer to the methods of SAR raw echo generation and simulation, thepre-processing of raw echo method before imaging and the detection algorithm ofspecial target after imaging.The first chapter is introduction. In this chapter, we first introduce the history andpresent situation of SAR. And then we give a brief explanation to some basicknowledge that we need.The Second chapter focuses on the research of SAR raw echo generation andsimulation methods. Basing on the existing mixed time-frequency domain method, wepropose a new mixed time-frequency domain method, which has a better result.In the third chapter, we do some research on pre-processing of echoes, which focus on how to provide a better accuracy for the subsequent imaging part in low SNR.According to the characteristics of the signal analysis of SAR systems, the dissertationintroduces the FrFT filtering method to process raw echo, which makes the systemachieve a good performance.The fourth chapter investigates target detection in special background. And wepropose a new ship detection CFAR algorithm in the sea clutter background. Accordingto the simulation results, we find that this method has a better detection performance,which can get less false targets than traditional method in the same false alarmprobability.