Study On Passive Radar Imaging Of Movingtargets Using Illuminators Of Opportunity

Passive radar is a radar system which doesn’t emit electromagnetic signal, it uses a variety of external radiation sources to achieve passive detection and imaging.Therefore it has good characteristic of electronic countermeasure.In recent years, with the development of science and technology, illuminators of opportunity are widely distributed and the number of them is increasing. Besides, the passive radar based on illuminators of opportunity not only can obtain the good characteristics of electronic countermeasure, but also can save the cost of the system and saving frequency resources,it becomes a research hotspot again. On the other hand, moving target is a very important kind of radar target, detection and imaging technology for moving target is always an important research content in the field of radar. Based on the above aspects, this paper carries out the research on passive radar imaging of moving targets using illuminators of opportunity, such as worldwide interoperability for microwave access(WiMAX), wireless fidelity(WiFi) and so on.First, it briefly introduces the concept and imaging techniques of passive radar, then reviews related research status at home and abroad, and presents the research background, significance and main content in this paper.Second, it studies the inverse synthetic aperture radar(ISAR) imaging technology with illuminators of opportunity. ISAR is a high resolution imaging radar for non-cooperative moving targets, it can be used for target recognition. As the ISAR imaging based on illuminators of opportunity belongs to the bistatic ISAR, the paper first describes the bistatic ISAR imaging principle, as well as the ISAR motion compensation and imaging method, and then gives the specific imaging methods and imaging process of ship target in complex sea condition. Finally, experiments are carried out to verify the passive ISAR imaging performance by using the WiMAX signal.At present, most existing imaging methods assume the source information is known or through other means to get, then take the best match processing to the received echos. However, the source information is often hard to get and tend to increase the hardware cost of the system. This paper put forwards a kind of passive detection and imaging method without any transmitted information. The method based on the generalized likelihood ratio test(GLRT) theory, and can applies to both cooperative and non-cooperative situations. Then, according to the point spread function(PSF), the spatial and velocity resolution of the resulting image is analyzed. Finally different configurations of receivers and sources are considered to obtain the influence on imaging.Next, base on the results of free space, the passive distributed aperture radar imaging under multipath environment is reseached. About the past processing, most algorithms are directly inhibit the multipath signal and don’t consider it into imaging. This paper establishes the model of echo in multipath environment and introduced the multipath components into imaging, then to investigate the positive and negative effects of them on imaging.Since most illuminators of opportunity with a narrow bandwidth, resulting in a poor imaging range resolution, a multi-channel synthesis technology is applied to improve the range resolution of the system. It first establishes the multi-channel signal model and derives the related processing method, followed by the corresponding characteristic analysis and experimental simulation with multi-channel DVB-T signals. The results show that the range resolution of target imaging is improved, which demonstrates the effectiveness of the technology.Finally, the thesis summarizes the full text work, and pointed out issues that still need to be further researched.