The Research On Digital Modulation And Demodulation Technology Based On Software-Defined-Radio And Its Application

Recently, with the development of communication technology, more and more concern has been given to the wireless communication because of its convenience and efficiency, but wireless communication is a very complicated process,especially some algorithms are difficult to master if theoretical study is the only way used.Realizing and studying by experiment is very necessary for the vast numbers of engineers and college students.The SDR, Software defined radio, proposed a novel mode of wireless communication with standardized, modular and open characteristics.Also,the technique of modulation recognition has been improved dramatically as an important technology basis of SDR.This paper is based on a lot of literatures and relative design schemes,and according to the actual need,put forward a general thinking of use now available SDR experimental system to simulate the wireless communication by programming.There are encode,modulation and demodulation included.Through the experiments,the learner can understand the wireless communication in depth, and also can learn the SDR technique visually,so a greater effect of learning can be achieved.The design of this paper is made up of two parts, the one is the design of software environment,and the other is modulation and demodulation algorithms of specific modulation types.The software environment includes the VHDL program of CPLD,control and display program of MCU,and so on.The algorithm part is about the modulation and demodulation of some common modulation types based on DSPs. Besides,the thesis attempts to probe into the modulation recognition by theories,and provides a recognition method based on higher order cumulants.Then provides a correction for this experimental system and multipath interference of wireless channel. This research laid a solid foundation for the realization of modulation recognition on the system in the next stage.With the situation of running and carrying out of the project,this work is greatly useful and credible.It is very applicable in the field of teaching and research.