Study And Implementation Of Modulation Recognition Technology Of Digital Communication Signals Based On Channelized Receiving

The carrier frequency and Modulation method are both important characteristics of communication signal. It is an important research filed of communications reconnaissance, whose purpose is to determine the modulation method and modulation parameters in the complex and noise jamming signals environment, so as to provide a basis for further analysis and processing. The aim of recognition is to identify the modulation method through analysis and processing the received signal absence of prior information. With the development of communication technology, a large number of new modulation technologies were put forward, which make it even harder to determine the modulation method. With the characteristics including wideband instantaneous frequency coverage, fine frequency resolving power, proper sensitivity and dynamic range, simultaneous signal detection, the channelized receiver is being widely used in reconnaissance receiver. The major work of this paper is shown as follows:First, the theory of channelized receiving is introduced, and its implementation on FPGA is discussed too. The channelization method is adopted because that the sampling rate of ADC of this system is up to 1.2GHz, which other components can not matched.The results of simulation and data validating approve that it can be used properly. Then, the problems of estimation of carrier frequency and recognition of modulation method are discussed. Because that we need a proper frequency estimation accuracy to recognize the modulation method, the interpolated DFT method is adopted to enhance the frequency estimation accuracy. In order to make clear how about the channelized receiving effect on the precision of frequency estimation, some simulation is done, whose result indicates that the channelized receiving can advance the estimation precision. It makes a research of how to recognize different modulations of digital communication signals such as ASK, PSK, FSK and QAM. The recognition algorithm accords to the theory of statistical pattern recognition. Seven characteristic parameters from frequency, amplitude and phase are constructed and extracted. Through a large number of simulations, the threshold value of each characteristic parameter for modulation recognition is confirmed. According to the characteristic and threshold value for the characteristic parameters, a decision structure of the tree classifier is designed and realized.Finally, the engineering realization of the modulation recognition on a development board system is described. The structure of the system is introduced in particular. Then the pretreatment of the signal processing is described. At last, the pipeline structure and parallel structure are adopted to implement the modulation recognition of digital communication signals based on optimizing the algorithm of digital communication signals modulation recognition.