Development of a small and long-life ultrasonic biotelemetry system strong against sea ambient noise

A highly efficient ultrasonic biotelemetry system would be desired to the ocean having a high underwater ambient noise that is especially from the temperate zone to the tropics. The four parameters were defined as the estimated factors for pinger system, long distance transmitting, battery life, pinger size and ability of recognition. The four parameters of the pinger were analyzed and investigated to design for the optimum ultrasonic biotelemetry system. The first parameter, long distance, must be considered the transmitting frequency, modulation, transformation and etc. The second, battery life, must be designed for the effective transducer and the low power dissipation electronic circuit. The third, smallest pinger size, must be adopted the microelectronics components. The last, high recognition, depend on the signal processing method of the underwater transmitting system . As a result, the first need was achieved over 1,200 meters transmission distance, the second was realized 300 days battery life when 30 seconds repetition by using the small battery SR626SW 32mAh. The third, the pinger size was realized theφ8 mm diameter and 40 mm long. The last, the M sequence signal was used the pinger and the correlation processing of the receiving system was adopted for the high recognition against the noise and to avoid the collision of other pingers. The system consisted of the tiny pinger and the high performance receiving equipment including the transducer. The pinger could be transmitted the IDs and the depth information each repetition interval. The receiver processed to correlate the received Msequence signal from the pinger using the FPGA chip and calculates the direction of the pinger. The raw data could be stored to the PC through the data conversion from analog to digital, 16 bits 192 kHz sampling. The actual experimental data will be presented to obtain in the Tokyo Bay and Osaka Bay using the developed system.