Adaptive Array Processing of HF Signals Propagated Over a 2600 KM Path
Final rept. 1 Jan-31 Dec 1972
COLORADO UNIV AT BOULDER
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The purpose of the study was to investigate the potential advantages which may accrue to HF antenna array systems by employing adaptive beamforming techniques. Data for the study were obtained using a CW transmitter located in Bearden, Arkansas and an eight element, narrow band 31.25 Hz receiving array in Los Banos, California. The Bearden signal was presumed to be an undesired interference. The individual array element signals were combined using tapped- delay-line filters for purposes of rejecting the Bearden signal while simultaneously forming a beam in the direction of a weak desired signal. It was shown that adaptive adjustment of the delay line weights provided better than 25 db improvement over conventional beamforming methods. The adaptive time constant was measured as 27,000 adaptations for each 3 db improvement, corresponding to a real time rate of less than 100 msec for special purpose digital hardware.
- Radio Communications