Phase-Inversion Symmetric Method Application In Frequency Domain And Studies Of Noise Correlation

The change of Communicate environment especially artificial noise which has become the main noise fountain, more attention has been paid on how to use noise correlation to enhance SNR. Eliminating the noise in channel by making use of correlation of band limited noise and the correlation of it's numerical characteristics is the basic theory of Phase-Inversion Symmetric Method, by using this theory, weak signals can be extract from strong noise and the SNR is increased greatly. "Phase-inversion" means that the signal and its reversed signal are sent simultaneously (the inversed signal means that the amplitude is inversed of the signal). "Symmetric" means two signals are disposed on the same way .The interferences also are alike when the two signals are transmitted at the channel. Finally we subtract the inversed signal from the signal. If the interferences of two signals are the same completely, the interferences are eliminated. If they are equal, the final signal is double of the first signal. Generally two interferences may be not homology. But if they are similar, noise also can be eliminated. The available degree and application area is decided by noise correlation coefficient p between different noise. The key is how to confirm the size of p.Computer simulation and circuit experiment are carried out to confirm the validate of the method.Selecting the 2FSK system as a example, this paper has analyzed and simulated the application of Phase-Inversion Symmetric Modulation theory in the frequency domain and proved the correlation and feasibility of PISM of the noise in practical system.Special computer simulation software-SYSTEMVIEW is used to substantiate 2FSK communication system. Because 2FSK system is compose of tow 2ASK and reciprocal digital signal transmitted separately by the two 2ASK is consistent in PISM system. So 2FSK system is the application of PISM in frequency field. The simulation results indicate that the academic BER is head and shoulders above the practical BER.These phenomenon confirm the noise correlation which is use by 2FSK to reduce the error rate. The classical theory presumed channel noise is AWGN which have no correlation, so the situation is inconsistent with the facts. We have also improve the relation between p and size of channel bandwidth, distance of border upon channel. The more narrow of bandwidth and more near between channels, the bigger of p.2ASK and 2PSK system are both simulated in the same condition and the result of academic BER is the same as practical BER, The reason is that these two systems which do not use noise pertinence to advance SNR are different from 2FSK.Experiment circuit is designed base on simulation, Firstly, test circuit id designed using EWB software and the result indicates communication reliability can be assured on input SNR=1:200. The test of experiment circuit state clearly that error rate is not found on input SNR=1:25. These results far exceed theoretic value.Finally, the summary and the plan are provided in the paper. Improvement of PISM model in time and space is the emphases in future.