Experiment on influence of the communication signals transmission in plasma sheath

A vehicle flying in the atmosphere at transsonic velocity creates plasma sheath, and the communication signal is defiladed or its energy is attenuated by the plasma sheath, thus the communication system is discontinued between the vehicle and the signal station. The phase changed and the energy absorbed of the communication signal in plasma sheath which is made by the shock tube was studied, and the experiment of different plasma parameter was finished. Two measuring systems were built, one is the signals generator and data sampler, and its modulation is quaternary phase shift keying (QPSK), and its carrier frequency is 7.5GHz; the other is the E8362B test system. The contrastive results of the signal phase changed and the signal energy attenuated at the plasma and no plasma were obtained. The experimental results show that not only is affected the communication by the plasma sheath absorbing, but also the phase changed of QPSK signals is achieved, the signals demodulated/decoded are badly aberrant, and the P_e of communication system is increased, and the receiver is unable to offer the original information sent by transmitter.