Digital Communication Signal Modulation Recognition And Parameter Estimation

The modulation recognition of communication signal and parameter estimation are an important research area in digital signal processing. It has been widely used in adaptive receiver, the monitoring of signal spectrum and radio interception. With the rapid development of communication technology, the style of communication signals becomes more complex, so modulation recognition is also becoming more important. The purpose of modulation recognition is to correctly recognize the modulation type of communication signal when the prior information is insufficient, and estimate the modulation parameters for demodulation.This thesis designs a new type of digital communication recognition and demodulation system based on Software Defined Radio (SDR). First, this system uses the improved periodogram (Welch procedure) and the constant false alarm rate (CFAR) process to detect signals, then uses the quadrature digital down converter and variable decimator to improve signal-to-noise ratio. Through extracting signal instantaneous characteristic parameters, the recognition of the2FSK, GMSK, BPSK, QPSK modulation and two navigation signals can be done. Finally blind estimate signal modulation parameters and demodulation. The symbol rate estimation using cyclic autocorrelation characteristic of the digital signal. The digital algorithm of timing recovery uses the square circuit with digital filter and three-order Lagrange equation interpolation. The histogram statistical algorithm of pulse repetition interval (PRI) is used to recognize the TACAN and JTIDS navigation signals. The computational complexity of modulation recognition algorithm which is used by this thesis is small, and this algorithm has good expansibility.