The Research And Design Of Receiving System In Marine Search And Rescue Radar Transponder

Marine Search and Rescue Radar Transponder (SART) is a device widely used inthe area of the safety of the ship. Its main function is to help vessels in distress to reporttheir position to the search and rescue radar. When signal from the radar in search andrescue ship or helicopter received, it will immediately reply a group of specific signal tosearch and rescue radar. So that the rescue boats or helicopters can determine theposition of the vessels in distress by the information displayed on the radar screen. Thiscan dramatically shorten the search and rescue time and reduce the people’s life andproperty damage caused by maritime accidents, that makes search and rescue efficiencygreatly increased. The main structure of SART consists of antenna, receiving portion,the emission portion and the control part. The receiving part is made up of low-noiseamplifier, detector and pulse shaping circuit.The transmitter part is made up of thevoltage-controlled oscillator and power amplifier. And a CPLD chip makes up the mainpart of the control module.In this thesis, the work contains the following main points:(1)First, combined with the GB15216-94international standard that formulated byGlobal Marine Distress and Safety System(GDMSS), the function and workingprinciple of SART will be analyzed, and the design plan formulated.(2) The system uses a sharing power supply method of receiver and transmitter, it’sbeneficial to the low power consumption, and can realize the isolation. Transmitting andreceiving antenna is a microstrip conformal omnidirectional antenna which usehorizontal polarization, have a omnidirectional roundness less than3dB, gain5dB,vertical beamwidth not less than±12.5°,VSWR≤1.8. The low-noise amplifier isdesigned with a hetero junction FET named NE3210S01which produced by the NEC.With the help of ADS, simulation and design show that the gain of LNA is greater than10dB. The detector select SMS7630-040LF zero bias Schottky diode to design with abalanced structure, its VSWR≤1.6, and detection sensitivity is not less than270mV/mW. Pulse shaping amplifying circuit use the structure of the three limiteramplifier to design, Small level pulse signals within a certain amplitude range can be amplified and shaped into a regular square wave, with a stable amplitude in the range ofCPLD logic level.(3)Finally, the work is testing the sample component. A test of the whole systemhas been carried on before comparing with the indicator. The result show that receivingsystem is working properly and it can reply the signal correctly.