Clutter Reduction Algorithm Research Of Intra-wall Microwave Imaging

Penetrating radar for detecting near surface target is a kind of emerging radar system which has high range and azimuth resolution and favorable penetrating ability, thus can be used to detect, discern and image the small targets buried in the shallow surface of non-metallic medium(such as concrete wall and plywood, etc.). However, in the process of application of Penetrating radar, because of the small distance between antenna and the small target, the direct coupling wave of the transmitting and receiving antenna, as well as the reflecting wave of the medium surface are coupled with effective target echo. Besides, the amplitude of the direct coupling wave and the reflecting wave of the medium surface are much more stronger than the target echo, thus will seriously affect the discernment and imaging of the shallow-burying target. So how to effectively suppress the clutter is of critical importance to the improvement of penetrating radar system performance,This paper proposes different kinds of parametric estimation clutter reduction methods according to the characteristic of Penetrating SAR, which are suited for Single-pair antenna and Antenna-array penetrating radar, respectively. The main contents are as follows:1. According to the different working and scanning mechanism of Single-pair antenna and Antenna-array Penetrating SAR, this paper builds different receiveing radar signal model of each of them respectively, and develops electromagnetic models of two main coupling clutter: direct coupling wave between transmitter and receiver and the reflecting wave of the medium surface.2. Based on basic parametric estimation clutter reduction method: empty background cancellation and mean cancellation method, it proposes two modified clutter reduction methods, such as, subdomain mean cancellation and prestore direct-coupling wave cancellation method which are all applied for Single-pair penetrating radar system to suppress the reflecting wave of rough medium surface. Detail algorithm principal and flow are presented. The experimental results show that these methods can effectively suppress the coupled clutter and greatly enhance the image results,and modified clutter reduction algorithms can diminish the effect of the medium surface roughness as well.3. In order to suppress the clutter existed in Antenna-array penetrating SAR system, this paper proposes several modified parametric estimation clutter reduction methods based on the difference between Single-pair antenna and Antenna-array system, such as empty scene cancellation method, scanning line mean cancellation method, subdomain scanning line mean cancellation and prestore direct-coupling wave reduction method. These methods are all proved to be effective to suppress the coupled clutter and greatly improve the image results and radar system performance.4. At last, this paper analyzes the computing complexity and clutter reduction performance of different clutter reduction methods applied to Single-antenna and Antenna-array Penetrating SAR and the reason why the remains of clutter appeared beside the target in the result image. Then the different precondition of those clutter reduction algotithms and both their advantages and disadvantages are compared.