Heterodyne laser radar SNR from a diffuse target containing multiple glints.

A coherent laser radar performance model is formulated using the Huygens-Fresnel principle for a near-field or far-field diffuse target which may contain a number of glints. The received signal is calculated for a truncated Gaussian-transmitted beam mixed with a matched Gaussian or a uniform local oscillator (LO) beam. In general, the uniform LO beam provides a good or better mixing than the matched Gaussian beam. The effects of beam truncation and receiver aperture size on the received signal level are presented. In the case of a far-field diffuse target, an increase in SNR is obtained if the receiver aperture increases to about three times the transmitter aperture, or if the transmitter aperture increases to about three times the receiver aperture. The target signature statistics and the weather statistics are considered as random parameters in the evaluation of receiver performance characteristics.