A Research Of 1090ES Capacity Extending Technology Based On Phase Modulation

Mode S 1090 ES is one data link of ADS-B system, its capacity can be extended. The 1090 ES expansion technique based on phase modulation can effectively increase the information capacity of 1090 ES data link. This expansion technique makes full use of the phase information in PPM high level data bit pulse with phase modulation, meanwhile it doesn’t change the standard data link format of recently 1090 ES signal. This thesis mainly studies the key technologyies in 1090 ES expansion technique based on 8PSK phase modulation, the main content involved including framework of system modulation, channel coding, carrier synchronization and decoding algorithm of 1090 ES expansion signal. The main work is as following:(1) The thesis analyzed expansion scheme of 1090 ES data link. The system modulation/demodulation architecture of 1090 ES expansion signal is designed, and the mathematical model and expansion data link model of 1090 ES expansion signal is given.(2) The RS code check technology in 1090 ES expansion system based on 8PSK phase modulation is studied. The total length of the RS code is designed as 54, and then determines the optimum selection of RS coding efficiency as 0.6 ~ 0.7, through the study of error performance and the influence on performance of 1090 ES expansion system under different RS coding efficiency. Further, the number of information code is choosen as 32, 34 or 36, through analysis RS code error performance under the selected coding efficiency.(3) A new carrier frequency synchronization method applicable to 1090 ES expansion signal is put forwarded: coarse estimation and accurate estimation. Coarse estimation can narrow frequency deviation to 5k Hz; the residual frequency offset after coarse estimation is estimated and compensated with accurate estimation based on phase error tracking loop or segmently feed-forward differential method. The correct decoding probability of phase information based on phase error tracking loop estimation method is greater than 0.91, when SNR is higher than 6d B. As for accurate estimation based on segmently feed-forward differential method, the normalized mean square error converges to Cramer-Rao Bound when SNR is higher than 1d B, and when SNR is 3d B, the correct decoding probability of phase information can reach 0.91.(4) The decoding algorithm of 1090 ES expansion signal is analyzed. Baseline multipoint judgment and coherent demodulation based on PPM information methods are used respectively, to extract PPM information and phase information in 1090 ES extended signal. The correct decoding probability of PPM datas can reach 0.9917 and the correct decoding probability of phase information datas can reach 0.9134, when SNR is greater than 3d B.