Study On Adaptive Interference Suppression Technology Using Mismatched Filtering

Artificial and non-artificial external interference are the major performance limiting factors of high frequency radar. Especially when the interference falls into the main lobe, the beam pattern is distorted with conventional adaptive digital beam former for the sake of suppressing the main-lobe interference. The major study content of this paper is the interference suppression technology based on mismatched filtering.In this paper, the Principle of traditional coherent side lobe cancellation (CSLC) is analyzed. Through the establishment of the interference in HF radar working environment and the simulation results proved that CSLC method cannot suppress main lobe interference. A system for suppressing external interference is proposed based on CSLC and the analysis of generation and correlation property of Frank codes. he radar data are processed through the main channel's matched processing module and virtual auxiliary channel's mismatched processing module in this system. Then the outputs of these two modules are put into an adaptive beam former based on coherent side-lobe cancellation algorithm.Besides, two improved schemes called large target rejecting method and twice process system are proposed which can solve the problem of elevation phenomenon when all the data participate in the adaptive weighting calculation. Effectiveness is confirmed by simulation results of single target and interference as well as multi-object and multi-interference, especially in the main lobe interference suppression.Finally, a system using mismatched filtering and subspace projection is proposed. Simulation results show the effectiveness of this system. Furthermore, it is designed simply and operated. However, this system is used perfectly when the interference does not enter the main lobe of array antenna. Therefore, it is necessary to improve this system.