Characterization of a wideband monopulse piezoelectric direction finder

Abstract

Sound localization has been the subject of much ongoing research in the area of beam­formers and microphone arrays. Although these methods have been successful under certain conditions, the signal processing requirements needed for real-time operation are extensive. This thesis describes the construction and test of a piezoelectric monopulse direction­finding sensor used to determine the angular location of a source within the plane of the sensor. The design of the sensor exploits spatially derivative-matched sensing apertures to eliminate angle ambiguities and frequency dependence of the monopulse ratio. The electronics front end and processing are very simple, consisting of averag­ing the sample-by-sample ratios of the rectified-and-smoothed outputs during their reverberation-free time period. Several experiments are described with different inputs, and the sensor's operation is compared to theoretical and simulated behavior. Although the effects of the hexcell support on the spatial weighting of the sensor are not fully understood, it is shown that the sensor behaves as a dispersionless monopulse sensor for an angular range of ± 40° and a bandwidth of 4 kHz. It is also shown that the sensor does not, in its current form, produce adequate signal levels to be used as a speech localization device.