| Airborne phased array radar will be affected by sea clutter when detecting flying targets over the sea.Therefore,the problem of sea clutter suppression about airborne radar has received widespread attention.In addition,in modern warfare,the airborne phased array radar often faces various interference signals from attackers,which is also not conducive to radar target detection.In order to suppress interference,it is necessary to locate the interference signal sources.The array signal direction of arrival estimation has become an important research content in the field of radar target detection.This thesis has done the related research work around the above two aspects.The main work of the thesis is summarized as follows: 1.An airborne radar K distribution sea clutter simulation model based on SIRP method is established.In the existing statistical amplitude models,the K distribution can not only describes the sea clutter based on the sea surface physical scattering mechanism,but also accurately simulates the temporal and spatial correlation characteristics of the sea clutter,while the Weibull distribution and the Log-normal distribution are based on single-point statistics and cannot reflect the spatial-temporal correlation of sea clutter.For the simulation models of sea clutter,the spherically invariant random processes(SIRP)can independently control probability density function and correlation function of the clutter,while the zero memory non-linearity does not meet this condition.In addition,the traditional SIRP model is only suitable for monopulse radar,however,the airborne radar is a multi-pulse continuous sampling system.To solve the above problems,an airborne radar K distribution sea clutter simulation model is established by using the SIRP and combining the airborne radar pulse sampling principle and clutter data characteristics.Through simulation experiments,the K-distribution sea clutter sequence that fits the characteristics of airborne radar is obtained,which has spatial-temporal correlation.2.A sea clutter suppression method based on two-dimensional pulse-to-pulse canceller(TDPC)is proposed.Although the traditional reduced-dimension STAP algorithms can suppress sea clutter,various errors in practical applications and the property of the time-varying of the sea clutter cause the sea clutter spectrum to broaden,and it is not possible to obtain enough independent and identically distributed samples.The clutter suppression ability of the traditional reduced-dimension STAP algorithms is reduced.To solve the above problem,the two-dimensional pulse-to-pulse canceller based on prior knowledge is used as the sea clutter pre-filter,and the sea clutter is pre-filtered before the reduced-dimension STAP processing.By comparing the sea clutter power spectrum before and after TDPC pre-filtering,it can be seen that TDPC can form a filter notch along the sea clutter distribution trajectory to filter out side lobe clutter and part of the main lobe clutter;by comparing the improvement factor curves of the reduced-dimension algorithms and the reduced-dimension algorithms cascaded with TDPC,it can be concluded that on the basis of TDPC,the cascaded reduced-dimension algorithms can further suppress sea clutter and improve the overall performance of airborne radar sea clutter suppression.3.A fast DOA estimation algorithm based on human behavior algorithms(HBA)is proposed.The traditional MUSIC algorithm uses a grid search strategy for DOA estimation,which has large calculation amount and long operation time;the swarm intelligence algorithms has the disadvantages of slow convergence speed and easily trapping into a local point when estimating DOA angles.To solve the above problems,the HBA that efficiently solves the global optimal solution of the nonlinear function is used to search the MUSIC spectral peaks,so as to quickly estimate the DOAs of the interference signals.Simulation experiments show that the proposed algorithm has higher spectral peak search efficiency and higher DOA estimation accuracy than the swarm intelligence algorithms and the traditional MUSIC algorithm.In addition,the proposed algorithm has higher angle resolution than the traditional MUSIC algorithm in DOA estimation. |
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