| With the development of modern communication technology,communication system is becoming more and more complicated,the traditional hardware circuits are no longer able to meet more and more diversified demands,so the Software Defined Radio technology has received worldwide attention due to its flexibility and expansibility.As an important function of the Software Defined Radio technology,automatic modulation recognition technology has become a research hotspot,especially in the field of non-collaborative communication.For the sake of reliability and effectiveness of automatic modulation recognition and demodulation,this paper fully studied the communication signals modulation theory,and gives a good algorithm of real-time power spectrum estimation,then focuses on analyzing several important parameter estimations:symbol rate estimation,frequency offset estimation and symbol timing error estimation.Some improvements are proposed for the existing algorithms,and the simulation results show the effectiveness of the algorithm.By analyzing the current research results in the field of automatic modulation recognition,this paper presents an automatic modulation recognition algorithm flow with high accuracy,and performs a lot of analysis and simulation at every step of the algorithm to select better parameters.Then the algorithm is synthesized,and the recognition rate of the integrated modulation recognition algorithm under different SNRs and the reason analysis are given.The research of this paper is based on the RTL-SDR receiver.After the theoretical research,software is written to realize the research content,and the implementation details of signal reception,frequency conversion,filtering,decimation and modulation recognition are introduced.This paper also demodulates some actual communication signals including FM and ADS-B broadcasting signal.And the operation of the software verifies the accuracy of the signal processing,recognition and demodulation algorithm. |
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