Design Of The Emergency Position Indicating Radio Beacon Tester

With the development of the marine industry, various countries attach great importanceto the safety of offshore production operation. When ship is in trouble, the crewman can useemergency position indicating radio beacon (EPIRB) to emit a distress signal, this is a goodway to improve the success rate of rescue. Nowadays, in order to guarantee emergencycommunication emergency position indicating radio beacon has been widely equipped in ship.In order to facilitate daily testing and maintenance of the EPIRB device on the ship, this paperput forward a design scheme of EPIRB tester, which is based on software defined radio.At the beginning, this paper introduces the basic theory and critical technology ofsoftware defined radio and analyzs the characteristic of the EPIRB signal. Combined with thefunctional and performance requirements of the EPIRB tester which is required by theCOSPAS/SARSAT, this paper put forward overall design schemes of the tester. The EPIRBtester divides into three parts according to the function: time measurement module, carrierfrequency measurement module, signal demodulation and bch decoding module. How torecognize the endpoints of the signal is the key of measuring time parameters. Firstly, EPIRBsignal is detected from the background noise through energy detection. Then the starting pointof the modulated signal is detected through phase detection algorithm. Finally, the endpoint ofthe EPIRB signal can be used to get gating signal. After this, we can complete themeasurement of time parameters combined with electronic counting method.Since the testerneed to measure the carrier frequency of eprib signal, this paper put forward frequencymeasurement algorithm which combine Costas loop with fast fourier transform. In thismethod, the frequency obtained by the FFT operation will be used to initialize the Costasloop，then epirb signal is tracked with a Costas loop.This approach not only shortens thetracking time but also enhances the frequency measurement accuracy.At last, the validity of the proposed approach is demonstrated by computer simulation.Simulation results illustrate that the algorithm presented has good performances and thedesign scheme of epirb tester can meet the requirements.