Weak Signal Detection Technology For Synthetic Aperture Ladar

Synthetic Aperture Ladar (SAL) is a new laser imaging radar combining Synthetic Aperture Radar (SAR) in the microwave band with ladar, whose resolution is much higher than SAR's resolution and which also can provide long-range and large-scale imaging. SAL which only needs the smaller optical aperture can provide higher resolution images. It has been the research focus at home and abroad.When remote objects are detected by use of SAL, the weak echo signal is usually interfered by noises. The coherent detection is difficult to carry out, so the heterodyne signal needs to be amplified and processed properly. In this paper, the weak signal detection technique of SAL is discussed. The potential noises in the heterodyne system are analyzed, and the noises introduced by the photodetector are especially studied. With regard to the weak signal of SAL, the photoelectric receiving circuits of PIN and APD are designed combining the integrated broadband amplifier with the microwave band-pass filter for the purpose of reducing noises and improving the SNR of the system. The weak output voltage signal of the photoelectric device is amplified and filtered. The results obtained in the experiment are analyzed by means of MATLAB software. The selection of optical detection circuit in different experimental conditions is summarized in order to achieve the best experimental results.