A double refresh rate sonar ring with FPGA-based continuous matched filtering

Existing sonar rings are limited in their refresh rate to the transmit echo rate, that is, waiting for maximum range echoes to arrive before transmitting again. This paper presents a sonar ring refreshing at 60 Hz for 5.7-m range, which is twice the transmit echo rate, and this leads to lower latency, denser measurements. Two custom Field Programmable Gate Array signal processors provide real time continuous match filtering with dynamic templates. A new method is implemented to select the transmit time from a random set based on minimizing interference. Experiments demonstrate the increased refresh rate, interference rejection, and maps generated by the sonar ring.