Directional detection system

摘要

A directional detection system including a microphone assembly comprising an omnidirectional microphone and two orthogonal directional microphones. The omnidirectional microphone signal is connected to a phase lock loop comprising a sweep generator connected to drive a voltage controlled oscillator where the output signal of the oscillator is compared in a phase detector with the microphone signal. Upon registering a match and satisfying a predetermined signal-to-noise ratio the phase lock loop locks on to one spectral component of the microphone signal, the sweep is terminated and the loop tracks the signal by integrating the phase detector output signal and further controlling the oscillator therewith. The integrated detector output signal, or the loop error signal, is connected to an enable unit which produces an enable signal when the error signal is within a predetermined frequency band and exceeds a predetermined amplitude. The enable signal is connected to a plurality of narrow bandpass tracking filters set to pass a frequency determined by the oscillator, the filters being respectively connected to receive the omnidirectional and the directional microphone signals. The enable signal activates each tracking filter and the respective output signals thereof are connected to a frequency converter which converts the signals into respective sidebands. The sidebands are then compared in phase, generating an azimuth signal referenced against magnetic north.