CHARACTERISTIC OF PLASMA SHEATH CHANNEL AND ITS EFFECT ON COMMUNICATION

The plasma sheath communication blackout issue for hypersonic or reentry vehicles is addressed from a channel characteristic perspective. Different from previous research, this paper emphasizes the importance of plasma sheath channel in the study of plasma communication blackout, and the discussion on transmission and phase shift characteristic of plasma sheath channel and their effect on communication performance was made with detail. A mathematical plasma sheath channel model is proposed and following the roadmap about how to obtain channel characteristic parameter is given. Flow field simulation of a blunt conical body physical was made, and the electron density and collision frequency profile got from flow field result under different incident angle at Mach 10-20 are presented thoroughly. The performance for QPSK based communication system under the established plasma channel is evaluated finally. It is indicated in our research that channel attenuation feature variation regularity is consistent with that of incident wave or Mach number, but the phase shift variation regularity with incident frequency or Mach number appears fall into chaos because of multiple 360 degree removal of original phase shift from communication view and complicated ratio relationships among incident wave, plasma frequency and collision frequency. Communication simulations result show that bit error rate agree with phase shift chaos well and phase shift exert large influence on present typical racking, telemetry, and command system. Some useful implications obtained from this study to improve communication performance include high frequency, high power and further rapid acquisition/tracing phase-locked loop compensating large phase shift.