抄録
The position communication system to rescue a drifting diver in marine has been studied. The practical equipment, however, has not developed, as there still exist several subjects to be solved. There are some restrictions posed to the equipment to be used in marine, such as the size, reliability of the position, and communication distance of low power radio regulated by the law. We adopted a low power radio transceiver to avoid the regulation and a spread-spectrum system in order to extend the communication distance. We are trying to adjust the PN code is generated at both transmitter and receiver to obtain further extension of the communication distance by using the PPS signal by a GPS receiver. At the transmission side, the data and the PN code are triggered by PPS signal every second. They are multiplied each other. At the receiver side, down conversion and A/D conversion are performed in the RF section of a receiver, and digitized signal was introduced into FPGA. The signal is despread by the PN code synchronously generated with the PPS signal and the data are obtained. The preliminary experiment shows a possibility of 5 to 10 times longer distance communication than the conventional low power radio transceiver.
