The Design Of Mode S Automatic Dependent Surveillance-broadcast System Analog Signal Source

With the strong development of air traffic and civil aviation industry, higherrequirements are present for the space utilization in the new era. In order to achieve the "freeflight"vision, ADS-B came into being for the last decade. Mode S is the only link moderecommended by the ICAO and its communication bandwith can reach1Mbit/s, further moreit can broadcast information real-time. The ADS-B system own higher update rate, highersurveillance precision, but lower cost of construction and maintenance. Also it can supplysurveillance for the blind area of traditional secondary radar surveillance management.Theadvantage of ADS-B indicates that it will inevitably become one of the effective ways of airtraffic management, so the research of ADS-B technology has great significance.Mode S data link is one of the most advanced ADS-B system link format.The papermainly focuses on the data format of the Mode S data link, the encoding method, theinterference of same frequencies and the modulation scheme. It construct theoreticalfoundation for the signal resource of ADS-B receiver system and finally apply direct digitalfrequency synthesis technology to it.It also support test signal so as to verify the signalprocessing functions of the ADS-B baseband signal receiver.S mode signal source system structure design in this artical are constituted by the dataconfiguration interface of the host computer and the slave machine FPGA controling output.Host computer mainly use VC++development platform complete CPR encoding, Mode Caltitude encoder and CRC code check algorithm.It also add serial port sending module tocomplet sending data to slave machine. The slave machine mainly complete PPM encoding,reported head synthesis processing and control ADI’s direct frequency synthesis chip AD9854to output variable frequency carrier and stable carrier for the IF signal ASK modulation. Italso increase the AD9280serial-to-parallel conversion chip digital baseband signal output.Finally complete a multiple signal generator which can achieve analog baseband output,digital baseband output, the variable IF signal output and the transmission error codes output.It provide stable S-mode analog signal source for the research and test of the ADS-Bbaseband receiver.