Research Of Method For Airborne P-Band SAR Radio Frequency Interference Suppression

Since 1950 s,Synthetic Aperture Radar(SAR)has applied in many fields.SAR is a kind of high-resolution radar,and can work at all day and night,which is able to work better on large region for imaging.The airborne SAR system has also gained enormous success.Because of the longer wave,the airborne P-band SAR has better penetrability,and is exerting an increasingly vital effect in military reconnaissance?geographic detection?hydrologic supervision and resource probing.In the complex electromagnetic environment,there are a lot of civilian wireless equipment of P band,the signals generated by which will enter the SAR receiver,and seriously affect the performance of SAR imaging.The signals sent by the civilian equipment are called Radio Frequency Interference(RFI).In this article,the methods about RFI suppression for P-band airborne SAR system are studied.Chapter 1 introduces the background and significance of the research,and has summarized the present status of SAR system and RFI suppression in recent decades.Chapter 2 founds the model of P-band RFI and analyzes the influence of RFI for SAR imaging.The models of RFI for single and multi-channel SAR system are respectively introduced,and their characteristics are also concluded.From the gain of SAR itself,the influence of RFI for SAR performance is analyzed.Chapter 3 presents a kind of joint filter for RFI.The traditional notch filter and subspace projecting method are introduced,and are compared with the joint filter.The joint filter has more accurate judgment for RFI and better value for the frequency bins.Chapter 4 proposes a kind of oblique projection filter for RFI,which is built according to the space geometry of RFI.Comparing the traditional spatial filter,there is no relativity of different RFI in the novel method.And the contrast experiments on point target and area target are done.Chapter 5 brings up a kind of space and frequency filter,which expands the processing field from single dimension to double dimension.On the basis of the properties of high power and narrow band,the frequency band of RFI can be separated and filtered by space filter afterwards.Compared with space filter,the new method can effectively decrease the loss of useful signals.Chapter 6 is the conclusion.The present work is concluded and the future plan is also listed.