Study On Some Issues Of Coast-Ship Bistatic Surface Wave Over-the-Horizon Radar

Much attention has been paid to HF surface wave radar for its abilty to detect the over-the-horizon targets. The coast-ship bistatic surface wave over-the-horizon radar uses an coast-located array to transmit signals of different carrier-frequencies and a ship-carried omni-antenna to receive echoes. The energy emitted covers a rather large sector and the equaveillant transmit beampattern is formed by adopting the technique of impuslse and aperture synthesis. As a bistatic HF radar, this radar system is considered effective to contour the threats existing in the modern high-technology war scenario, such as stealth target, anti-radiation missile, composite electronic jamming and low-flying target penetration. What's more, the receiver carrier can moving freely and feasibly and no beam-chasing is required which is necessary in a traditional bistatic radar. Operating as both surveillance and tracking radar, this system is able to detecting and tracking several targets at the same time. Focusing on some issues of this radar, the main content of this dissertation is summarized as follows:1. A brief introduction is given to the radar system and its characteristics. What follows is the processing flow of multi-carrier LFMICW, with an emphasis on the transmit pattern synthesis process. The waveform parameters are designed based on the LFMICW signal and the system requirement. The resolution of this bistatic radar is deduced and simulated.2. The system synchronization and the transmit array calibration are studied. The time and frequency synchronization information is obtained from the direct wave because the radar receiver is moving and no wire or cable link for comunication is available to transmit synchronization signals.The technique of calibrating the transmit array at the receive station by using the direct wave is presented, which is based on the fact that the receive plat is moving and its direction is known. The error matrix composed of array gain, phase and sensor location uncertainty is estimated using the direct wave signals received by the moving receiver in three different directions. Two methods are given to estimate the error matrix, which are called as Covariance Matrix Fitting(CMF) method and Subspace Fitting(SF) method respectively. The real data and the computer simulation verify the validity of synchronziation and calibration methods.3. The problem of range-angle coupling is discussed. The coupling coefficient is deduced from the amplitude-comparison theory and the Fisher information matrix. Based on the coupling coefficient, the method of optimizing the carrier frequency arrangement for decoupling is put forward. The CRB of range and angle estimation is deduced from the Fisher information.4. Based on the analysis of the direct wave interference, the interference suppression in the time, range-angle and Doppler domain respectively is presented. These three methods for direct wave suppression are evaluated from the aspects of computation complexity, processing gain and output SINR. Finally the simulation and real data results are given to prove the effectivity of these methods.5. The channelized receiver in this radar is studied. Intuitively, the channelized receiver is composed of low-pass filter bank, which will lead to rather a computation load because the filtering is performed at a high date rate. To improve the efficiency, the channelized receiver based on polyphase filter bank is adopted where the date is first decimated and then filtered hence the computation complexity decreases largely. The design of the prototype low-pass filter is discussed and the computer simulation is given.6. The spatial-temporal characteristics of the sea clutter in this bistatic radar are analyzed, which is followed by the clutter suppression in image domain. The spatial-temporal spectrum is first transformed to a image, and then the sea clutter at one range bin is eliminated using the images at the adjacent range bins. The computer simulation tells that the sea clutter can be suppressed by using this method.