Utilising Airborne Bistatic Radar for Target Detection and Imaging

Palmer, James Edward (2007). Utilising Airborne Bistatic Radar for Target Detection and Imaging PhD Thesis, School of Information Technology and Electrical Engineering, University of Queensland.

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Author Palmer, James Edward
Thesis Title Utilising Airborne Bistatic Radar for Target Detection and Imaging
School, Centre or Institute School of Information Technology and Electrical Engineering
Institution University of Queensland
Publication date 2007
Thesis type PhD Thesis
Supervisor Dr John Homer
Abstract/Summary In bistatic radar, a spatially separated transmitter and receiver are employed for target detection and/or imaging. The use of bistatic geometries has implications for the apparent Radar Cross Sections (RCS) of targets and can allow detection of targets that are stealthy in monostatic (i.e. collocated transmitter and receiver) scenarios. Bistatic radar has been an on-going area of research since the original development of radar early last century. However, it has only been with the recent improvement of signal processors that the full possibilities of the bistatic geometry may be investigated. In this thesis, we consider a number of variations on the standard bistatic geometry and employ several novel detection and imaging algorithms that exploit some of the advantages provided by bistatic radar geometries. Specifically we consider the Shadow Detection technique, the Emulated Bistatic Radar (EBR), the EBR for synthetic aperture radar (SAR) imaging, inverse SAR (ISAR) imaging and interferometric purposes, as well as bistatic ISAR imaging. The Shadow Detection technique utilises the variation of the received signal power from constantly transmitting satellite sources, such as the GNSS satellite systems, as a detection method. Two signals are received by an airborne receiver that is flying over the open ocean. The first signal is the direct Line of Sight (LOS) from the satellite, whilst the second is received from the sea surface reflection in the quasi-specular region. Both signals are studied for signal strength variations that are otherwise unexplained by any variation in the system geometry, and in the case of the sea surface reflected signal, by sea surface scatterer variation. The presence of an unexplained signal strength variation may indicate the presence of a target somewhere along either of the received signal paths. In this part of the thesis, consideration is given to the detectability of targets and at what range they can be detected, as well as what signal modulation effects are introduced to the received signal as a result of the target’s presence, which would assist in target size and range determination. We consider theoretical, simulated and experimental results in support of this detection and ranging technique. The Emulated Bistatic Radar (EBR) detection technique is similar to the Shadow Detection technique in that it utilises the reflective nature of the sea’s surface, however in the EBR we employ an active airborne monostatic radar as opposed to the parasitic use of illuminators of opportunity. The EBR uses the sea surface to create an indirect illumination path to the target, whilst focusing its receiver on the target directly. This introduces a bistatic angle into the detection geometry that will change the apparent RCS of the target. For low monostatic RCS targets, this RCS gain could be such that the effective detection range and probability of detection of the radar is improved. We also explore the use of the EBR with highly coherent imaging techniques such as SAR, ISAR and interferometry. In this thesis, we present a theoretical discussion with simulated, experimental, and real world results that verifies the usability of EBR in these imaging scenarios. Lastly, we consider the use of conventional bistatic radar geometries with ISAR imaging. In this section we present a theoretical discussion, as well as simulated and experimental results that demonstrate the viability of using ISAR imaging techniques with conventional bistatic geometries.

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Created: Fri, 21 Nov 2008, 15:21:44 EST