The Dynamic Plasma Sheath Of PM Signal Adaptive Decision Method

The reentry vehicle or the near space high speed vehicle returns to the atmosphere at the 10~25 Maher velocity,the air is squeezed by the body to form a shock wave,and produce violent friction with the surrounding air.The air molecules are ionized by high temperature,and a plasma sheath is wrapped on the surface of the aircraft.The plasma sheath will deteriorate the communication quality,which can lead to the disruption of the information link.This is known as the "black barrier" phenomenon.Because of the turbulence of the plasma sheath boundary layer and the different attitude of the aircraft,the plasma sheath presents a complex dynamic.The dynamic characteristics of dynamic plasma sheath will bring amplitude attenuation(amplitude noise)and phase jitter(phase noise)to the communication signal.Even though the electromagnetic wave can penetrate the plasma sheath,the amplitude noise and phase noise introduced by the parasitic modulation effect seriously reduce the communication quality.In this paper,a new decision method is proposed,which is based on the parasitic modulation effect on the phase modulation signal:1.introduces some key theories of plasma and the phase modulation signal,explain the dynamic plasma parasitic modulation effect mechanism,electromagnetic wave transmission coefficient is deduced through dynamic plasma are a special class of spiral line.The effect of parasitic modulation on the phase modulated signal is analyzed theoretically.The plasma generating device in the laboratory,experiments are carried out to verify the effect of parasitic modulation effect on phase modulation signal,the spectrum of the experimental results and eye diagram and constellation are analyzed,at the same time is simulated,the simulation results and experimental results are basically consistent,dynamic ion experience constellation of distortion caused by phase modulated signal,rotation.2.from the supervised learning point of view,the strong correlation of plasma channel dynamic characteristics of reflected and transmitted waves,to predict the channel characteristics by measuring the reflection wave,the establishment of training examples,put forward new decision algorithm based on support vector machine,in order to improve the accuracy of judgment,at the same time using the autocorrelation of singular value decomposition method and moment estimation method of to estimate the channel signal-tonoise ratio,improve the accuracy of judgment.The simulation results show that the algorithm is accurate and effective.3.from the perspective of supervised learning,according to the dynamic plasma caused by the phase modulation signal constellation special rotation characteristics,an adaptive decision method based on spectral clustering,spectral clustering has some manifold learning ability,simulation and experimental results show that the major part of the decision,the method has good judgment effect.However,when the phase modulation signal constellation overlaps,the decision algorithm is invalid.In this paper,inspired by machine learning,intelligent algorithm is applied in the field of dynamic plasma demodulation,two new adaptive decision algorithms are proposed.Simulation and experimental results show that the algorithm is effective.It provides a new way to solve the problem of black obstacle and to realize the reliable transmission of the information in the plasma sheath.