Study On Coast-Ship Bistatic HF Surface Wave SIAR System And Relevant Techniques

Owing to a low attenuation of vertically polarized HF radio wave on ocean surface, HFSWR is able to detect the targets of 300~400Km away. So it can be considered as complementary of HF sky wave radar and conventional microwave radar; and it also can be applied to the remote sensing of ocean state in real-time, large range and 24-hour working. Therefore, HFSWR plays important roles in the management and development of exclusive economic zones (EEZ) for oceanic countries.This paper studies a novel HFSWR—coast-ship bistatic high frequency surface wave SIAR (Synthetic Impulse and Aperture Radar). Using the SIAR technique, the radar successfully combines bistatic and shipborne operation. Thus the radar has the advantages of flexibility and the ability of rejecting directional active jamming and ARM (Anti-Radiation Missile). The researches of the paper are outlined as follow:Chapter 1 introduces the background and necessary of coast-ship bistatic high frequency surface wave SIAR. The history of HFSWR and some typical systems are firstly reviewed. The contents of the paper are also presented.Chapter 2 introduces operation principles of the novel radar. According to the signal processing flow, the system configuration and framework are firstly presented, and then the operation principle is introduced detailedly by introducing the system synchronization, the parameters selection and synthesis processing of LFMICW, and coordinate transform and location; finally, some key techniques in signal processing are discussed in brief.The demands of the radar on signal waveform can be met by selecting the parameters, and the experimental results show the feasibility of the radar.Chapter 3 studies the configuration of transmit array and range-angle joint superresolution processing based on transmit array. The operation performance of Minimum Redundancy Linear array (MRL) as transmit array is investigated in resolution, estimation precision with MUSIC algorithm. The frequency code is selected for releasing the coupling between range and angle with GA (Genetic Algorithm). The calibration of channel errors of gain and phase is proposed using the direct wave from the transmit site.The analyses show that MRL has advantages over ULA or plane array in system cost, element coupling and resolution; the orthogonal waveform with frequency code is better than that with the phase code of the same frequency for the improvement of system resolution and range precision.Chapter 4 studies the suppression of radio frequency interference (RFI) when only a single omnidirectional antenna is utilized. The features of RFI in time, range and Doppler domain are analyzed firstly; and then the orthogonal projection algorithm is utilized to mitigating the time and range domain RFI. The new methods for estimating the covariance matrix is propose based on the features of RFI. The algorithm is examined with the practical data.The experimental results prove that the proposed method can effectively suppress the RFI without the distortion of target pattern even when the RFI is spatially nonstationary.Chapter 5 investigates the characteristics of sea clutter with a single antenna on a moving receiver platform. Based on the mechanism of first-order sea clutter, the Doppler frequency of sea clutter is formulated about the system geometry. The space-Doppler coupling and time-modulating of sea clutter are discussed.The spectrum of sea clutter will be widen when the receiver is moving, which directly lead to the difficulty in detecting such slow targets as ships or boats.Chapter 6 studies how to suppress the spreading sea clutter. The Hankel rank-reduced matrix method based on singular value decomposition (SVD) is applied in beam space; and spatial adaptive filtering with Doppler pre-processing is also tested; finally, two space-time adaptive processing algorithms: mDT-SAP and JDL (Joint Domain Localized) with Direct Data Domain (DDD) method are tried to suppress the clutter. The simulation results show the validity of the above methods.Chapter 7 makes conclusions about the study of the paper, and some problems to be solved and future working are presented in the end.