COHERENT DOPPLER SODAR SONDE R AND D

AN IMPROVED ACOUSTIC WIND PROFILER IS PROPOSED, MEASURING VELOCITIES TO 100 KNOTS WITH A 2 KNOT RESOLUTION, TO HEIGHTS > OR = TO 3 KILOMETERS. TO ACHIEVE THIS IMPROVEMENT IN PERFORMANCE OVER EXISTING ACOUSTIC PROFILERS, THREE TECHNIQUES ARE BORROWED FROM UNDERWATER ACOUSTICS AND APPLIED FOR THE FIRST TIME TO WIND PROFILING TECHNOLOGY.THESE ARE: (A) A PARAMETRIC TRANSMITTING ARRAY, (B) COHERENT TRANSVERSE DOPPLER PROCESSING OF SCATTERED ECHOES AND (C) CODED PULSE SEQUENCES. NON-LINEAR ACOUSTIC INTERACTIONS AT THE SOURCE PRODUCE A LOW FREQUENCY (500 HZ) TRANSMITTED PULSE IN A NARROW (APPROX 10 DEG) BEAM WHICH IS TOTALLY FREE OF SIDE LOBES, AN IMPORTANT FEATURE IN COVERT SYSTEMS. THIS IS ACCOMPLISHED IN A PROJECTOR OF ONLY 63 CENTIMETERS IN DIAMETER. THE RECEIVERS (MICROPHONES) ARE SEPARATED BY ONLY1.2 METERS, FURTHER ENSURING SYSTEM COMPACTNESS. BECAUSE OF LOW ABSORPTION LENGTHS AT 500 HZ, ONLY 1.11 WATTS OF RADIATED POWER ARE REQUIRED TO GIVE A RETURN ECHO FROM A HEIGHT OF 3 KILOMETERS, WITH A RECEIVED SIGNAL TO THERMAL NOISE OF 20 DB UNDER WORST CONDITIONS. COHERENT DEMODULATION OF THE DOPPLER SIDEBANDS, FREQUENCY (WIND SPEED)ESTIMATION, DISPLAY AND TABULATION ARE ACCOMPLISHED DIGITALLY. PHASE I EFFORT PROVES CONCEPT AND OPTIMIZES PARAMETERS TO ACHIEVE CONCEPT DESIGN OF OPERATIONAL SYSTEM.