Receive Antenna Arrays Synthesis And Non-stationary Interference Mitigation Algorithm For Over-the-horizon Radar

Over-The-Horizon radar (OTHR) usually work in the high-frequency (HF) band(3~30MHz). The trait that the receive and transmit signal are reflected through theionosphere layer make OTHR break through the limit of Earth’s curvature to achieve thegoal of over-the-horizon detection. It is widely concerned as it owns the advantages oflow cost, large area detection, stealth targets detection and so on. However, in modernworld, emerging homeland security require rapid deployment, low cost, quick modeswitching HF system. So the huge OTH radar array usually need to be deployed on theirregular terrain, which posed a serious challenge to the array performance. Moreover,due to the dynamic properties of the ionosphere layer and the user-congested highfrequency band, interference often present non-stationary characteristics, which causethe degradation of the performance of traditional spatial filtering algorithm.This paper focuses on the issues, the main work are summarized as follows:(1) Study on the synthesis of OTHR receive antenna arrays in irregular terrainThe impact of uneven terrain on the performance of array pattern is analyzed, and aphase compensation algorithm is proposed through the investigation of the relationshipbetween the phase difference of adjacent elements and the terrain slope. With theproposed algorithm, the distortion of the array pattern caused by the uneven terrain iscorrected. Then a sparse array model and a synthesis method which combined phasecompensation and Dolph-chebyshev algorithm is suggested due to a specific irregulardeploy environment. The simulation results shows that the final array pattern meet therequirement of the OTHR, and prove the conclusions above.(2)Study on the synthesis of OTHR sub-array level sparseAccording to the requirement of flexible sub-arrays networking, a sub-arraysspacing constrained array optimization method is suggested. Moreover, the sub-arraylevel weighting based on Genetic algorithm is used to depress the side-lobe level.Finally the simulation results is gived to verified the effectiveness of the array optimization method proposed in the paper.(3) Study on adaptive non-stationary interference suppression algorithmSeveral adaptive beamforming method based on non-stationary interferencemitigation techniques are analyzed theoretically, and their performances are evaluatedusing the simulation experiment results. The reason that the de-coherence of the seaclutter between the pulses in the piece-wise adaptive beam-forming is verified.According to this problem, a beam-pattern constraint non-stationary interferencesuppression algorithm and its general side-lobe canceller structre is proposed, which cansuppress the non-stationary interference while effectively preserving the temporalcoherence of the sea cluter echoes. Based on updating the weight vectors to suppress thenon-stationary interference, this algorithm design a constraint function on the bases ofthe root reason of the problem, thus greatly reduces the fluctuation. At last, theweakness of the algorithm proposed in this paper is overcomed by modifing the goaland constraint function. The final experimental results proved the conclusions above.