Optimization Method And Implementation Of Partial Response CPM Signal Spectrum Characteristics

With the milestone progress of digital communication technology.digital modulation and demodulation technology has also developed rapidly.Continuous Phase Modulation(CPM)has received more attention due to its advantages of smaller out-of-band radiation,envelope constant and higher spectrum utilization compared with traditional modulation methods According to the characteristics of CPM system,this paper studies the method of optimizing the baseband symbol of partial response CPM signal based on generic function modeling and improving the optimized energy spectrum signal by artificially introducing inter-symbol interference.It realizes the baseband symbol optimization of partial response CPM signal and the modulation and demodulation of CPM system.The main work of this paper includes the following aspects.1.It introduces the basic characteristics and principles of CPM signal.Then shows and compares the spectral characteristics of several typical CPM signals2.This paper discusses the method of phase optimization of partial response CPM signal by determining function.including polynomial function and cosine function.Then it demonstrates the specific derivation process and formula of applying the basic determination function to obtain the partial response CPM signal.The spectrum characteristic diagram of CPM signal with continuous smooth phase trace characteristic artificially introduced inter-symbol interference is drawn,and the spectrum characteristic is compared and analyzed3.This paper introduces the method of establishing generic function model by using the minimum out-of-band energy radiation criterion.It introduces Fourier series and energy restriction conditions.optimizes CPM frequency modulation function and CPM phase modulation function by using numerical method to realize approximate solution of optimized generic function model.What's more,it draws different symbol waveform diagrams and spectrum diagrams,and compares with the spectrum characteristics of MSK signal According to the calculation of power spectral density-40dB bandwidth and-60dB bandwidth.compared with MSK signal,the frequency band utilization rate has increased by 5 times and 11 times respectively.The transverse comparison is made for different power exponent n and different symbol time length T and the influence of signal length on spectrum performance is discussed.In addition,the influence of the number of terms in Fourier series on the accuracy of the optimization function is analyzed.4.The time-frequency characteristics of the partial response CPM signal are simulated by MATLAB simulation software,and the modulation and demodulation of the partial response CPM signal are realized on MATLAB,and the bit error rate is analyzed.The feasibility of the optimized CPM system is verified.