Study Of Ship Imaging And Real-time Processing Software

Inverse synthetic aperture radar (ISAR) is an essential candidate in military and civil fields. ISAR is widely used in information extraction for many kinds of targets, such as aircraft, spacecraft and so on. Ship imagery is an important branch of ISAR application. In this paper, both ships imaging theory and correlative real time processing techniques are studied.The ship imaging condition is very complicated since its complex movement containing translational and three-dimension rotation. Therefore to achieve ideal cross-range resolution is usually difficult. In this paper, we propose a pre-processor to divide and select the integrated time. The whole time is divided into several time segments according to the rotational motion characteristic, and azimuth processing is done for each of these segments independently. Using this method we can not only get better ship images but also improve the computational efficiency. Subsequently, four frameworks of azimuth processing in ship imaging are introduced.Multi-ships ISAR imagery with air borne radar is more difficult, because the targets can't be differentiated between range cells in single radar beam. What's more, motion complication of ships together with motion error of flying plane increase the difficult of motion compensation during ISAR processing. This paper demonstrates a method that using joint SAR-ISAR techniques to obtain ships images. First we abstract roughed focused objects from SAR image containing many ships, then pick up the ship signal which is interested in and transform it from image domain to data domain. Finally use ISAR method to obtain the single ship image. In real application, there are two processing methods base on long integration time and short integration time respectively. This method is validated by real data.In addition, real processing is a very important for the study of ship imaging. This paper also describes a kind of real processing system background of one institute. In this system, the signal processing board is mainly comprised of a FPGA and 6 DSPs. DDR2 SDRAM is used as the external memory of FPGA and SDRAM as that of DSPs. This paper presents the realization of the signal processing software, which includes realizing ship imaging algorithm on DSPs and realizing controllor of DDR2 SDRAM on FPGA. This software has been validated with outdoor experiment.