A self-adapting sonar ranging system based on digital polarity correlators

The logic capacity of programmable logic devices has reached a level which allows their use as digital correlators in sonar signal-processing applications. The devices can be modified at almost any point during use in response to changes in the input data or processing environment. This paper reports on the development of a self-adapting ultrasonic system consisting of digital polarity correlators for multiple-user ranging. The digital signal-processing system is integrated into the single programmable logic device. The system is able to provide good performance in different conditions by automatically changing both the signal that drives the transmitter and the range properties of the matched filter receiver. Such an approach allows distance measurements up to a few metres while still eliminating frequent misreadings caused by crosstalk or external ultrasound sources with the low-cost piezoelectric transducers.