| Too many varieties of modulation schemes in modern wireless communication system make it hard for different systems to communicate with each other. Conventional receiver has high dependence on hardware and bad adaptability to signals. The emergence of software radio results in the renovation of receiver technology, whose basic idea is realizing every kind of communication function flexibly through installing different software in the same hardware platform.In this paper, some key technologies of software radio, including the multi-velocity signal processing, communicating signal recognition and so on, are researched deeply. Due to the limitation of devices, special chips are utilized to build the digital IF receiving system.Firstly, some basic theories in the realization of the IF digital receiving system of software radio are discussed in detail, including basic signal sampling theory, band pass signal sampling theory and extraction technique of the signals. Secondly, automatic recognition of the communication signals modulation is studied. A new recognition algorithm based on SOFM Neural Network is presented according to the decision-making method. Experimental results indicate that the recognition rate is 1.6 percent higher for low SNR signal and same well for high SNR signal by comparing Neural Network recognition method with conventional technology. Next, setting the FM signal receiving as an example, proper software radio receiving system is designed and the parameter configuration and signal of FM demodulation are introduced. The receiving process is simulated by Matlab and the satisfying results are acquired. Finally, AD6640 converter of AD company, HSP50214B digital down conversion chip of Intersil company and DSP evaluation board-C5410EVM of WenTing company have been used to build a system of software radio IF digital receiving system. The results validate the correctness of the designed software radio receiving system. |
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