Four-element receiver for pulsed 10-mu m heterodyne Doppler lidar

A four-element photomixer receiver has been tested in a 10-mu m heterodyne Doppler lidar. It addresses a reduction of the variance of the power scatte red off distributed aerosols targets at ranges as long as 8 km. An improvem ent in performance is expected when the four independent signals recorded o n every single shot are combined. Two summation techniques of the four sign als have been implemented: a coherent summation of signal amplitude and an incoherent summation of intensities. A phasing technique for the four signa ls is proposed. It is based on a more suitable correlation time with discer nible self-consistent packets (SCP's). The SCP technique has been successfu lly tested, and the results obtained with a coherent summation of the four signals, i.e., variance reduction, carrier-to-noise ratio improvement, and velocity accuracy improvement, are in agreement with theory. (C) 2000 Optic al Society of America OCIS codes: 280.3640, 040.2840, 030.6140, 030.1670.