Study And Realization Of PISM-DSB Communication System

It is common practice to assume that the noise in a channel is AWGN in classical communication theories. But man-made noises which have strong correlation exist in most wireless communication systems, and their power is much stronger than natural noises. Therefore errors will arise when applying classical theories to modern communication systems. So it is significant actually to research channel model under correlation noise and method of eliminate correlation noise. This paper, Phase-Inversion Symmetric Method (PISM), makes use of correlation of band limited noise and its numerical characteristics to eliminate noises. It can be used to extract weak signals from strong noises. Also SNR will be increased greatly.In this paper, all kinds of noise are anylysed in communication system, and the method of measuring the noise correlation coefficient is introduced. We approve man-made noises have strong correlation. These noises influence on communication quality in morden wireless communication systems. The output SNR will be improved when we using the correlation.The basic principle of PISM is introduced .We clarify that PISM make use of the correlation of the noise and its digital character to eliminate the noise, explicit the relation between PISM and Shannon principle.This paper has done further studying to the application in DSB system of PISM on the basis of the thing that the past theory is analysed. The real circuit has been designed. There is strong correlation between upper-sideband and lower sideband. We can conver two groups of signals on the same frequency simultaneously, and two groups signals are not disturbed each other. Thus make the channel utilization ratio raised by one time.The simulations show that the isolation of two groups audio is 37dB and PISM-DSB is feasible.Modem based on PISM-DSB has been developed. PISM-DSB has the same results with SSB. It also can convey two signals, but it is difficult to carry on. PISM is achieved easier than SSB.At last, there is a sum-up about this paper. Later we will study the Phase-Inversion Symmetric transmission system with an equilibrium phase.