多输入多输出天波超视距雷达多模杂波抑制的改进最小方差无失真响应算法研究

多输入多输出天波超视距雷达(MIMO-OTHR)通常利用最小方差无失真响应(MVDR)波束形成来抑制接收回波中的电离层多模杂波对目标探测的影响。由于MIMO-OTHR的全向性发射、杂波噪声协方差矩阵估计不准确以及有限相干积累时间内训练样本数过少，使传统MVDR输出信杂噪比(SCNR)较低。对MIMO-OTHR中的MVDR算法进行改进，以改善其多模杂波的抑制能力。利用2阶锥规划进行发射波束域预处理，将发射能量集中到主模式角度；在阵列接收端进行阵列平滑，抑制主模期望信号，提高杂波噪声协方差矩阵估计精度；利用MVDR波束形成双迭代算法，降低对计算量与训练样本数的需求。仿真结果表明：改进MVDR算法可有效抑制多模杂波；以较少训练样本及较小计算量，可以获取更高的输出SCNR.

Improved Minimum Variance Distortionless Response Algorithm for Multi-mode Clutter Suppression in Multiple-inputMultiple-output Over-the-horizon Radar

For multiple-input multiple-output over-the-horizon radar (MIMO-OTHR), the minimum variance distortionless response (MVDR) is usually used to solve the impact of the ionospheric multi-mode clutter in the received echo on the detection of the target. The output signal-to-clutter-plus-noise ratio (SCNR) of traditional MVDR algorithm is low due to the omnidirectional emission of MIMO-OTHR, the inaccurate estimation of interference-noise covariance matrix, and a few training samples within a finite coherent accumulation time. Therefore, the MVDR algorithm is improved to enhance the multi-mode clutter suppression ability of MIMO-OTHR. A transmit beamspace preprocessing is realized by a second order cone programming (SOCP) to focus the energy on the principal mode angle, which is the transmit angle of the target path reflected by the ionosphere. The echo signal received by array is spatially smoothed to suppress the expected signal of principal mode and improve the estimation accuracy of interference-noise covariance matrix. A bi-iterative MVDR beamforming algorithm based on the beamspace preprocessing is proposed to reduce the computational load and the requirement of training samples. Simulated results show that the improved MVDR algorithm can be used to effectively suppress multi-mode clutter, and obtain higher output SCNR with fewer training samples and less computational load. Key