| Over the past three decades, significant advances have been made in the use of high frequency surface wave radar (HFSWR) for real-time and all-weahter remote sensing of ocean surface dynamic parameters, including wind, wave and current i.e. Compared to other measuring instruments, HFSWR has the advantage of high resolution, large area covering, real-time and lower cost. Because of these advantages and potentional exploration, so it is necessary to develop our own high frequency radar system for the security the country and the investigation of oceanic rescourses.With the quick development of electronics and computing technology, espascially Software Defined Radio (SDR), the performance of the remote sensing system have been improved significantely. Radiowave Propagation Lab. of Wuhan University has successfully accomplished the National High Technology 863 Project ’Research of Protable High Frequency Ocean State Measurement and Analysis Radar’, designed the first commercial HF radar system (OSMAR-S200), with a protable antenna and three-channel receiver, even more the system can acquire the noise outside the radar system, to make sure the frequency band we select is relatively ’pure’in the complicated electromagelatic environment. The thesis proposed a method which can realize a multi-state method, with the configurable time controlling module. During one radar operating period, the system can accomplich the echo receiving and noise acquiring with the time division technology. The modules of radar receiver are strictly controlled by synchronization controller. And with this time division technology, we proposed a new digital demodulation method as well, the new structure is more efficient and with higher performance, and further research has been done to achieve multirate sampling rate conversion. Besides that, another National Nature Science Funding Topic’Research and Modeling of UHF radar clutter reflected by ocean wave’. Our system can be configurated as UHF radar. This thesis gives the detail of UHF radar system design and field experiment.The content of the thesis is approximately as follows:1. Design method of multi-state radar system is proposed, with the configurable radar synchronization controller, the system can accomplisch more than one mission during one working period. In the paper, we use this technology to achieve the noise monitoring, and the design method of synchronization controller is given as well. With the noise we acquired, we could find a relative’pure’frequency band with less noise and interference, and the performance of the radar system is impoved, and during the field test, we use the professional spectrum analyzer to validate our noise monitoring design, it proves the design is reliable.2. In order to adapt the multi-state radar sytem design, a new digital signal processing method is proposed in this paper, which can achieve radar signal demodulation and sampling rate conversion without anti-aliasing digital filter used in the structure, in stead, a polyphase combinated with FFT structure is used for the demodulation, which is an efficient demodulation method. And even more the structure can be modified for modulation and demodulation, and multirate sampling rate conversion.3. As the radar system is an open platform, which can operate from HF to UHF frequency band. When the system operates at UHF frequency band, we have finished the experiment to research the backscatter by fresh water and salty water. The experiments at the beach of East China Sea and the Bridge of Yangtze River are introduced in this paper. And the experiments with frequency 4～5MHz,12～14MHz,25MHz and 305MHz are introduced as well. The radar parameters and echo spectrum are given, with the multi-state design; the system can be configured as time-devision dual-frequency system. The theory and system design are given for the realization. |
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