Design And Hardware Implementation Of Conventional Communication Signal Modulation Recognition System

Modulation type is an important feature of the communication signal.With the development of wireless communication technology,modulation type becomes more and more complex.Traditional use of artificial modulation recognition technology can not meet the actual demand,automatic modulation recognition which based on DSP,FPGA,and software radio technology becomes a trend.Automatic modulation recognition technology has been widely used in monitor the ship electromagnetic interference,radio listeners and other fields.This paper studies the basic principles of communication signal parameter estimation and modulation recognition.For 2ASK,4ASK,2FSK,4FSK,2PSK,AM,FM,LSB and USB of nine modulation signal,we propose a modulation recognition algorithm based on instantaneous statistical features and decision tree classifier.Compared to the previous algorithm,the algorithm of this paper can meet the actual hardware requirements:faster,less sampling points required and appropriate conditions for random symbols.Recognition algorithm using a new center parameters to improved {2ASK,4ASK} and {2FSK,4FSK}recognition effect.This algorithm uses an automatic threshold adjustment method,by selecting SNR reference parameter,a rough estimate of SNR is completed,so that the decision threshold can be adjusted automatically to improve adaptive of the SNR.Compared to the past a lot of algorithms,the algorithm is effective when the carrier frequency is unknown,it use a high-precision carrier frequency estimation algorithm CZT transform to meet the accuracy requirements of nonlinear phase extraction.Through MATLAB simulation,when sampling points is 1024(16 random symbols)and unknown carrier frequency,the algorithm has a good effect.When SNR is not less than lOdB,the average recognition rate reached 93.27%,When SNR is not less than 15dB,the average recognition rate is over 99.0%.The hardware platform which uses DSP + FPGA structure for modulation recognition is designed,the hardware circuit schematic and PCB design is completed.The DSP hardware circuit is passed signal integrity analysis(SI).In order to ensure the stability of the hardware circuit,we use SigXploer to conduct SI simulation for the circuit.We completed the commissioning of the hardware platform.In the CCS platform,the C language program recognition algorithms is be emulated,and stats recognition rate of recognition algorithm.Finally,we use the Design Hardware platform to identify five kinds of modulation signal which generated by the signal generator,and the experiment achieved the expected results.