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Study on Skywave Over-the-Horizon Radar Signal Processing

Author: GuoXin
Tutor: LiuGuoSui
School: Nanjing University of Technology and Engineering
Course: Communication and Information System
Keywords: OTHR Interference suppression Phase perturbations Multimode propagation Ship Detection
CLC: TN957.5
Type: PhD thesis
Year: 2004
Downloads: 836
Quote: 23
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Abstract

OTHR (Over-the-Horizon Radar-OTHR) in modern radar is more special, it works in the high-frequency band of 3-30MHz ionospheric reflection of the high-frequency signal from top Shimoji target detection. It against low-altitude and low altitude penetration, anti-radiation missiles and stealth aircraft has a natural advantage, at the same time be able to provide a wide range of early warning and early warning time far beyond the usual radar. Therefore, OTHR increasingly prominent role in modern air defense system, military significance. But the the OTHR high frequency band, ionospheric reflection work spread, and the next, as also makes it faces many problems in signal processing, the resolution of these issues to improve the performance of OTHR play the advantages of OTHR plays a vital role. In this paper, we and the Ministry of Information Industry Institute 14 collaborative projects - \The in-depth study. To sum up, mainly including the following aspects: (1) the OTHR of distance - orientation - Doppler three-dimensional joint approach detailed mathematical derivation and analysis of radar parameter settings based on the Barrick export scattering intensity formula analog marine echo spectrum, pursuant to which summarize the distribution of sea clutter characteristics and its dependence on the sea state characteristics. (2) details of the of OTHR in the interference and noise suppression. First of all, we from OTHR characteristics (including a huge range of monitoring, there are non-stationary interference) Departure, performance analysis and comparison of two adaptive beamforming scheme. Then specific adaptive scheme problems encountered in actual use, combined with the specific parameters of the radar is analyzed in detail. Next, for the non-stationary interference suppression, interference with the right to increase the adaptive update rate suppression method is discussed, theoretical analysis of the problems of this approach and give the simulation. Finally, our study focused on transient interference suppression propose to use adaptive time-frequency analysis technology - AGR algorithm simultaneously transient interference suppression and signal reconstruction. In this method, the base function of the variance of the time-domain and time-frequency center may be adaptively adjusted to each signal component, and thus better able to reflect the time-frequency detail feature. And transient interference suppression and signal reconstruction is completed at the same time, no longer need to step-wise, just when the domain decomposition of the signal will be smaller variance of the signal component removed, and then restructuring can. Therefore, it no special requirements on the number of transient interference in the coherent integration time, even if a larger number of transient interference, can still achieve better interference rejection and signal reconstruction. (3) in-depth study of the the OTHR ionosphere contamination correction. First, for ionospheric phase perturbations Solutions pollution, several Solutions pollution method current discussion and analysis of the advantages and disadvantages of each method. Subsequently, the measured and simulated data analysis phase of the severity of the pollution and the second-order spectral intensity solution contamination performance. Multimode propagation solution contamination of conversion based on multimode singlemode solution contamination analysis pointed out several problems that exist, then we propose multi-mode conversion for singlemode multimode, but directly in the cycle of the sea clutter subtraction elimination the multiple Bragg peak, which found the target. When the phase perturbations and multi-mode propagation at the same time exist, through theoretical analysis pointed out that the presence of multi-mode Bragg signal amplitude fluctuation makes filtered out than multimode when severe much Further leading to Bragg instantaneous frequency estimation error increases. , phase solution contamination performance degradation. For The multimode propagation Echo has a completely different phase perturbations of this complex situation, we propose the use of high-resolution linear time-frequency analysis method for processing the entire echo data. This method not only to solve the contradiction between the short-time Fourier transform temporal resolution and frequency resolution signal in detail features in the time-frequency domain, and further to find the target signal, which can be found at the same time without introducing cross terms. (4) in the part of the ship target detection, we first present several looks dry accumulation under the conditions of ship detection technology and CFAR approach to performance analysis and comparison. Then focus on the ship detection, and on the basis of the existing algorithms, improved sea clutter cycle analysis based on FFT phase cancellation law, compared to the traditional method, the new method can greatly improve the sea under the conditions of the accumulation of short coherence clutter parameter estimation accuracy and reduce the the remaining clutter strength and the degree of diffusion, which is conducive to the peak of ship targets revealed and distinguished from the remaining clutter ship signal. Finally, a summary of the full text, and further study of the problem need to be pointed out that the the OTH radar signal processing.

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