Advanced 2D/3D Imaging Techniques for ISAR and GBSAR

In chapter 1: The concept of the radar system has been introduced based on the radar block diagram. Moreover, there are some discussions about the radar equation, radar classification, and frequency of radar. In chapter 2: The fundamentals of radar cross-section are presented. Afterward, the RCS of two quadcopters is estimated by Electromagnetic Simulation Software (FEKO). In order to confirm the simulation, real measurement results are performed. Inverse synthetic radar (ISAR) processing are provided. In chapter 3: 2D And 3D inverse synthetic aperture radar (ISAR) image processing has been carried out for imaging small UAVs. The two-dimensional (2D) ISAR image is made by collecting scattered fields from different angles, while a 3D image can be obtained by integrating backscatter data in two spatial coordinates of the 2D aperture (cross-range in azimuth and elevation). Another topic that has been introduced is windowing in ISAR. In Synthetic Aperture Radar (SAR) processing the windowing in range and cross-range is a standard and its aim is to reduce the side-lobes of the Point Spread Function. In ISAR, when the rotation is smaller than 180°, the aperture windowing does not cause any estimation problems; it works exactly like a standard SAR. Problems occur when the rotation angle exceeds than 180° and especially when the rotation is complete. Therefore, for improving cross-range resolution in ISAR a new technique has been proposed. The rotation circle should be divided into four arcs of 180° before the focusing process, and a Kaiser window is applied on the chords of each of the arcs separately. Finally, the four resulting images are combined into one image as a radar image. In chapter 4: A new GBSAR system has been presented capable of generating both monostatic and bistatic images. Whereas the bistatic images need several hours to prepare the 3D information, the monostatic images are acquired in a few minutes by providing only 2D information about the targets in its field of view. Accordingly, the 3D measurement in conventional SAR radars is a computationally complex and time-consuming process but they can be interesting when the radar is used to image in a complex scenario. Due to this structure, it is able to create two images taken from different points of view with respect to the antenna system along an x-axis and the second channel along the z-axis. An advantage of proposed radar is that it can be operated as 2D interferometric radar for each horizontal scan, moreover, by varying the second channel height the 3D images are produced. It is worth mentioning that as a 3D image is obtained in bistatic condition, the angular resolution is worse with respect to a monostatic radar that scans a plan. In chapter 5: All concepts of compressive sensing have been discussed. The main bases and recovery methods are presented. Finally, the use of the CS algorithm in scenarios is carried out based on three different data. The first test is carried out with a corner reflector (CR) in front of the radar, the second one is performed with a seven-story building like the target, and the last one is accomplished in a natural scenario which was conducted with the "Belvedere Glacier" located on Italian Alpine.