The Research Of Modulation Identification Of Communication Signals

Modulation identification of communication signals is a rapidly developing high technology in recent years, and it is a critical part of signal analysis. Once upon a time, modulation identification is performed by analyzing the waveform and spectrum with the help corresponding equipments. With the development of micro-electronics technology, people started to explore ways of identifying signal modulation types with equipments with software kernels. Modulation identification technology has high practical value: In civil area, to enable effective wireless spectrum management, it is necessary to monitor civil signals to find unregistered transmitters, where both sign certificating and interference identifying involves with modulation identification; In electronic warfare, both electronic countermeasures and electronic counter-countermeasures employ modulation identification technique to check out the parameters and characteristics of relative communication or electronic signals. It could be seen from recently published articles in home and abroad, more and more attentions are being paid in the research of automatic modulation identification theory of communication signals, especially in the modulation identification under low signal to noise ratio. Different techniques, including spectrum related theories, high order statistics, artificial neural network, wavelet theories, are used or being used in the research of this area.This dissertation performed the following work based on others' work:(1) Studied the modulation identification problem of analogue modulated signals in depth, and successfully identified AM, DSB, SSB, and FM signals. Improved the existing key feature and designed identifying process.(2) Studied the modulation identification problem of digital modulated signals, successfully identified 2ASK, 2FSK, 2PSK, 4ASK and 4FSK signals. Introduced difference algorithm and sym4 wavelet in modulation identifying problem for the first time, and designed 2 identifying process.(3) After studying modulation identification problem of analogue and digital signals, emphasized on the conjoint identifying problem of analogue and digital signals. For the convenience of comparing with existing method, this dissertation covers only DSB, FM, 2ASK, 2FSK and 2PSK signals, the comparing result proves that the identification method in this dissertation reach better result.The dissertation makes a summarization and shows the prospect of the identification technology.