Msk Digital Modulation And Demodulation Technology Research

Software radio is an important research field and development in themodem communication technology. Now the limitation on developmentof software radio is the contradiction between the performance ofhardware and the enormous calculation in the signal processing. Sofurther researching the theory and putting forward the new methods andthe signal processing algorithm with the small calculation, especiallymodulation and demodulation algorithms, which is distinct significant toperfect and apply the software radio technology.In this paper, minimum frequency shift keying (MSK) is researched,which is a constant envelope modulation technology. It has thecharacteristic of continuous phase and high bandwidth utility. It is widelyapplied in the wireless communication system. The paper introduces thebasic theory of MSK, and analyses deeply the modulation anddemodulation methods for MSK, which the correlative papers mentioned,and points out some problems, then puts forward the improved methods.The carrier recover in the coherent demodulation for MSK is alsodiscussed. The methods of carrying the frequency shift carrier andmiddle carrier are put forward. The correlative analysis and conclusionsare validated by simulation. According to the request of software radioand the characteristic of MSK, the improved digital modulation anddemodulation methods for MSK are put forward. This digital modulationmethod uses the data of relevant code waveform to produce the MSKsignal, its grogram is simple and the calculation is small. Thedemodulation method uses the digital demodulation algorithm based onDFT. Its basic idea is to do DFT with the MSK signal samples in eachcode circle to calculate the signal amplitude correspond to the carrierfrequencies of 1 code and 0 code, then recover the digital signal byjudging the amplitude. The result of simulation indicates that thisalgorithm has the less calculation, the better antinoise performance, andthe less sensitive bit synchronization compared to the classicdemodulation methods.At last, aimed at the difficulty of carrier synchronization in the MSK, quasi-MSK signal is put forward whose module of frequency shift is h=1.It inherits the main advantages of MSK signal, and there is the frequencyshift carrier in the signal. It reduces the difficulty of carrier recovery andimproves the performance of error bit rate.