Research And Realization On Automatic Digital Modulation Recognition Algorithm Of Telemetry System

The automatic recognition of digital modulation types is applied to many fields such as signal identification, interference identification, radio interception, monitoring, etc. The objective of automatic modulation recognition is to identify the modulation type and estimate the modulation parameters without any prior knowledge about the signal information under the conditions of multi-signal circumstance and phonic jamming, providing adequate grounds for further signal selection and demodulation.In this dissertation, based on previous research and analysis of spectrum features and high-order statistics of communication signals, the identification of communication signals with Multiple Amplitude Shift Keying (MASK), Multiple Phase Shift Keying (MPSK), Multiple Frequency Shift Keying (MFSK), Quadrature Amplitude Modulation (QAM) modulation formats is investigated in depth.Firstly, beneficial from analysis of the power spectrum of the second and fourth power of signal, and the power spectrum of the amplitude of signal, a scheme, which is based on the spectrum features of telemetry signal for digital automatic modulation recognition, is presented. This scheme can discriminate modulation types commonly used in communication system. Also, it is proved to be feasible by simulations in different signal-to-noise (SNR) and different speed of symbol.Secondly, on the basis of the research of existed recognition algorithm using higher order statistics, an optimized algorithm for modulation recognition based on higher order statistics and moving average is proposed. Not only does the optimized algorithm can achieve higher recognition accuracy in low SNR range, also, it does not need apriori information about signal power. The theoretical principle of the optimized algorithm is deduced and analyzed. And its feasibility and practicability is verified through a lot of simulations in different SNR and different length of moving window.At last, an automatic digital modulation recognition and demodulation system of telemetry signal is developed using the optimized algorithm mentioned above, and digital quadrature demodulation algorithm in Software Define Radio (SDR). Then signal automatic modulation recognition and demodulation are united successfully.