Propeller driven vehicle locating arrangement - contains extended transducer arrangement, each contg. bandpass filter, envelope curve demodulator and low-pass filter, all feeding direction former

摘要

The arrangement contains an extended transducer arrangement with direction former (20) for producing a small aperture angle for evaluation of received sound waves from the vehicle. Each transducer contains a bandpass filter (50) and envelope curve demodulator (60) with a low-pass filter (61) of defined limit frequency. The pass band and limit frequency are selected so that the known propeller rotation frequency lies within them and the bandpass's centre frequency is essentially higher than the limit frequency. The max. transducer interval is half the quotient of the speed of sound and the limit frequency. All demodulator outputs are connected to inputs of the direction former. Output signals of direction channels with the highest levels define directions. USE/ADVANTAGE - E.g. for locating submarines. Small aperture angle, eliminates grating lobes and enables vehicle classification by evaluating received sound waves.