相控阵天线色散误差对高分辨率星载SAR成像质量的影响研究

Impact Study of Phased Array Antenna Dispersion Error on Image Quality of High Resolution Spaceborne SAR

对相控阵天线色散误差对高分辨率星载合成孔径雷达(SAR)成像质量的影响进行了研究。阐述了相控阵天线的色散产生机理,其影响可用实时延迟线对单元间空间路程差补偿消除。研究认为色散误差在距离向目标冲激响应函数中引入时变的方向图与辛格函数的卷积导致该函数出现畸变。建立了色散误差对星载SAR距离向点目标冲激响应的影响模型,计算表明完全延迟补偿时色散误差为零;部分延迟补偿时方向图随频率发生平移;无延迟补偿时带内平移更严重,且在部分角度位置发生剧烈的变化。分析了色散误差对信噪比、分辨率、峰值旁瓣比和积分旁瓣比等图像质量指标的影响。仿真结果发现:色散误差大小与延迟补偿成反比,补偿越多,误差就越小;随着色散误差增大,冲激响应函数畸变加剧,主瓣展宽、旁瓣抬高和变形,导致幅值也发生变化;波束边缘回波的冲激响应畸变较波束中心更明显。建立的模型和提出的分析方法已经经过了工程实践的检验,有较高的参考价值。

The impact of phased array antenna dispersion error on image quality of high resolution space borne SAR was studied in this paper.The dispersion mechanism of phased array antenna was described.The impact of the dispersion could be eliminated by real time delay line to compensate the space distance between units.It was believed that the dispersion would cause Sinc function distorted because of convolution between Sinc function and timevarying pattern which was introduced into target impulse response function.The impact model of dispersion on the impulse response was established.The computation results showed the dispersion was zero for full time delay compensation,the pattern was translated with frequency for partial time delay compensation,and the translation in band was worsened and the pattern would change greatly at some positions for no time delay compensation.The impact of dispersion on the SNR,resolution,PSLR and ISLR of SAR image was analyzed.The simulation showed that the more compensation,the less dispersion;the distortion of impulse function became serious while dispersion being large and the main lobe became wider as well as the side lobe became high and distorted which caused the amplitude changing;the distortion at the edge of the echo was larger than that at the center of the echo.The model and analysis method proposed has been proved in engineering which has its reference value.