Synthetic-aperture radar (SAR)

Synthetic-aperture radar (SAR) remote sensing is usually implemented by mounting, on a moving platform such as an aircraft or spacecraft, a single beam-forming antenna from which a target scene is repeatedly illuminated with pulses of microwaves at wavelengths anywhere from a meter down to millimeters. The many echo waveforms received successively at the different antenna positions are coherently detected and stored and then post-processed together to resolve elements in an image of the target region. SAR resolution is approximately equal to one-half the length of the actual (real) antenna and does not depend on platform altitude (distance). High range resolution is achieved through pulse compression techniques. Signal processing uses magnitude and phase of the received signals over successive pulses from elements of a synthetic aperture to create an image. As the line of sight direction changes along the radar platform trajectory, a synthetic aperture is produced by signal processing that has the effect of lengthening the antenna.

合成孔径雷达（Synthetic-aperture radar, SAR）遥感通常通过在航空器或航天器等运动平台上搭载单波束形成天线，利用该天线以波长覆盖米级至毫米级的微波脉冲反复照射目标场景。将在不同天线位置依次接收的大量回波波形进行相干检测并存储，随后联合后处理以解析目标区域图像中的各分辨单元。SAR的分辨率近似等于实际（真实）天线长度的二分之一，且不受平台高度（距离）的影响。高距离分辨率通过脉冲压缩技术实现。信号处理利用来自合成孔径各单元的连续脉冲接收信号的幅度与相位来生成图像。当视线路沿雷达平台轨迹发生变化时，通过信号处理可合成出等效延长天线长度的合成孔径。