| Author: | He, Zhenyu |
| Title: | Improving the performance of a GNSS based passive radar for maritime surveillance |
| Advisors: | Chen, Wu (LSGI) |
| Degree: | Ph.D. |
| Year: | 2022 |
| Subject: | Global Positioning System Hydrographic surveying Radar receiving apparatus Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Land Surveying and Geo-Informatics |
| Pages: | xiii, 148 pages : color illustrations |
| Language: | English |
| Abstract: | The exploitation of Global Navigation Satellite System (GNSS) as illuminators of opportunity to form a passive radar system has great potential in maritime surveillance and has drawn much attention in recent years. The GNSS constellations enable each point on the earth's surface illuminated by several satellites. Therefore, GNSS signals become one of the few emission sources available for maritime surveillance. As a passive radar system, only the receiver needs to be developed, which has the merits of small size, low cost, and safety due to its no electromagnetic radiations. However, since GNSS signals are not intended for radar purposes, this passive radar suffers from two main drawbacks: short operational range and low range resolution, due to the weak target signal energy and narrow signal bandwidths of GNSS signals. Although some relevant investigations have been made to handle the main issues of this novel passive radar, there are still some limitations. This thesis aims to improve the performance of GNSS-based passive radar applied for maritime surveillance. The main research contents are as follows. To increase weak target signal energy for target detection, this study proposes a long-time target signal energy integration method, known as Keystone Transform (KT) + Lv's Distribution (LVD), which can not only offer hybrid coherent and noncoherent integration gain for the weak target signal detection but also compensate the range and Doppler migrations that can reduce the integration gain. Both the simulation and real experiments are conducted to verify the proposed method, which shows that the detection ability of the proposed method is superior to some state-of-the-art long-time integration methods and with the same computational complexity. To enhance poor range resolution, this study puts forward a range resolution enhancement method based on the Incremental Wiener Filter (IWF), which uses a target detector to calculate the Peak Signal-to-Noise Ratio (PSNR) of the target response and exploits the IWF to improve range resolution by using the reciprocal of PSNR as the regularization parameter. Both the simulated and real experimental results show that the proposed method has finer range resolution enhancement over some existing range resolution improvement techniques and with higher computational efficiency. Once a moving ship has been detected, it is of interest to image the ship for target classification. However, few investigations focus on achieving the imagery of the detected ship. Therefore, this study investigates the possibility to image the ship target moving in the offshore or river channel area. First, a relatively simple bistatic acquisition geometry is defined. Then, an approximate bistatic range history is deduced to describe the phase variation of the target signal. Based on the approximate bistatic range history, a moving target image formation algorithm is proposed, which consists of six major steps: signal synchronization, range compression, range migration correction, moving target detection, motion parameter estimation, and azimuth compression. Finally, the feasibility of the proposed imaging algorithm is confirmed by both the simulation and real experiments. Meanwhile, the ship velocity, ship length, and moving direction can be accurately estimated. |
| Rights: | All rights reserved |
| Access: | open access |
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