Research On Receiver Array Calibration For Island HFSWR

High frequency surface wave radar is a new system radar with characteristics of all-weather, low cost, over-the-horizon etc. The existing HFSWR systems mostly adopt the linear receiving array. To achieve better angular resolution, the array area need to be increased. For the HFSWR installed on the island, it’s difficult to provide enough space to place the receiving array. Circular receiving array has become a research hotspots in recent years for its virtue of excellent super directional characteristics. This paper mainly focuses on the inaccurate DOA caused by the array error. The calibration method applied to linear array and the basic application of circular array have been studied based on the analysis of the array error’s influence.For the array amplitude and phase errors and mutual coupling error influence, this paper takes eight element uniform linear array as a model, and analyzes the array pattern distortion’s boundary where the error tolerance of the array has been given. Theoretical derivation proves that the pattern distortion’s boundary only relate to the error tolerance whether the amplitude and phase errors or mutual coupling error influence the array in random distribution. When the errors influence the array simultaneously, the pattern distortion’s boundary is the sum of each distortion’s boundary and their product. Finally, the simulation is used to verify the above conclusions.For existing linear receiving array, the amplitude and phase error calibration algorithms are comparatively analyzed. The STFD is used to improve the traditional algorithm, making its requirement for SNR reduced about 5d B and calibration capability for angular error improved about 10 degrees. Then the extraction method of calibration snapshots is studied, and snapshots extraction is achieved using sea clutter, the ship target and the ionosphere as calibration sources respectively. Finally, the target azimuth calibrated by the method in this paper and the target azimuth provided by AIS are compared. The experimental results prove its effectiveness.In view of the research of circular receiving array, this paper focuses on solving the problem of mutual coupling caused by the array miniaturization. Firstly, the array mutual coupling error model is analyzed by the improved equivalent circuit method, and the model is simplified by using the mutual impedance value obtained from simulation in HFSS. Secondly, the mutual coefficient estimation algorithms are compared and analyzed, hence the angle calibration accuracy achieved by the genetic algorithm is proved to be higher than by the cascade method. Finally, the mutual coupling coefficient estimation and the amplitude and phase error estimation have been done modular separation through iterative model constructed in this paper, so that the circular array calibration method becomes more flexible with mutual coupling. The effectiveness of the circular array calibration method is also proved through simulation and measured data processing.