Mode S Signal Processing And Application Based On GNU Radio

With the use of Mode S-based automatic dependent Surveillance –broadcast technology(ADS-B)in the new generation of air traffic control system,the research and application of Mode S and ADS-B are deepening.The ADS-B broadcast message is based on Mode S response signal(ie 1090 ES signal),and its data format is DF17 belonging to Mode S.Therefore,it is necessary to study in detail the processing of the Mode S response signal and the analysis of the DF17 data.On the other hand,with the rapid development of the aviation business,the demand for information transmission in air traffic is increasing,the problem of 1090 ES signal's capacity will become increasingly apparent.therefore,it is imperative to expand the capacity of 1090 ES signal.Based on the standard 1090 ES signal,this thesis makes a detailed analysis of DF17 data,and aiming at a 1090 ES signal expansion technology based on intra-pulse phase modulation,it studies the algorithm of modulation,carrier synchronization,PPM decoding and phase demodulation,which is used in the expansion technology.Also,using GNU Radio+USRP experimental platform,it achieves the 1090 ES expansion signal's transceiver processing.The main work is as follows:1?This thesis analyzes the DF17 data field and studies codec algorithm of some related information.Five types of ADS-B messages are analyzed in detail,including the field structure of the message and the coding definition of some related fields.It focuses on the coding of airborne velocity,the Mode C altitude coding algorithm and the Compact Position Reporting(CPR)codec algorithm of latitude and longitude in aircraft position information.The CPR coding algorithm can encode aircraft's latitude and longitude effectively into a 17-bit binary number of the message,which does not contain several high-order bits(such as latitude and longitude direction).The CPR decoding algorithm can decode the aircraft's position according to odd-format and even-format encoding.2?The 1090 ES signal expansion technology based on 8PSK phase modulation is studied,including the modulation of 1090 ES expansion signal,carrier synchronization,PPM decoding and phase demodulation of the receiver.Because of the discontinuity characteristics of the 1090 ES expansion signal,this thesis studies the segmented feedforward differential frequency offset estimation algorithm,and selects a best difference interval(10dT(28)?s)after a comprehensive analysis.The decoding performance of 1090 ES expansion signal is verified and analyzed by MATLAB simulation.Under the condition of 3dB SNR,the correct rate of PPM decoding can reach 0.9929,and the correct rate of phase information decoding is 0.895.3?Based on the GNU Radio+USRP experimental platform,transceiver processing of the DF17 data based on the 1090 ES standard signal and the 1090 ES expansion signal are realized,including the standard signal's PPR decoding and CPR codecs of latitude and longitude,the expansion signal's generation,header detection,PPM decoding,carrier synchronization and Phase demodulation,etc.Combined with matlab,a statistical analysis of the expansion signal decoding results is made,in the laboratory environment,the correct rate of PPM decoding can reach 0.99,and the correct rate of phase information decoding is 0.86.