| Though the VHF radar has a particluar advantage in anti-stealth, its inherent drawbacks such as wide beam width and less flexibility limit its further development. Consisted of several separated unit radars, the distributed radar system has the advantages of high mobility and easy expansibility. Combining the advantages of the above two radars, the distributed VHF radar has the capacity to ensure the anti-stealth performance, improve angle resolution, and to maintain mobility. These features reveal its broad developments prospects. Based on a distributed VHF radar project, this paper introduces the design of signal processing method, followed by the proceesing method of experimental data and the design of the signal processing software.Firstly, the principle, system structure, and operation modes of the experimental prototype are discussed. Then, with regards to the real work situation of radar, the design for system parameter is analyzed, according to which the power chart is given.Secondly, the methods for measured data processing of the system are analyzed and simulated respectively, including pulse compression, moving target indication, pulse accumulation, constant false alarm rate detection, and digital beam forming. Then a processing method is proposed to obtain precise angle measurement for distributed arrays, which combines coarse angle estimation of DBF(Digital Beam Forming) with fine angle estimation of ML(Maximum Likelihood) Array pattern is used to determine the search range of precision measurement. Simulation results show that there is no existence of grating lobes in above range, so it can be used to solve the problem of angle ambiguity. After that, methods for experimental data processing are discussed, including data extraction and processing methods for simulated target mode, normal single array mode, and distributed array mode. By comparing the phase of compressed echo peak value with the correction coefficient, the phase error of different channels is within 2o°and the phase fluctuations of each channel ≤0.5° in a certain observation time. By the signal processing of sub-array’s data in the normal operating mode, it is verified that the amplitude of channel can keep consistent, the trend of phase inversion is same as theoretical value, and the phase fluctuation of array elements is small. Besides, researches are carried out on methods for coherent synthesis in sub-array and SNR increase between sub-arrays.Besides,by the data processing result, the RMSE of angle measurement of distributed array is varifid to 1.02°.Finally, a radar test system is developed and then validated with real data. This system consists of two modules for simulated signal processing and real data processing. The first module is designed to verify the correctness of parameter design. It also provides feasible algorithms for the latter module, which deals with the offline processing of real data. The processing results show that this system works stably. In the simulated target mode, the system fixed delay is 8μs and the azimuth estimation error is less than 2°. In addition, the DBF directions of two sub-arrays are consistent. In the normal single array mode, the data processing result of a single sub-array shows that the root mean square error of track association is ≤85m and that of angle estimation is ≤2.25°. |
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