Research On The Impact Of Timing-varying Plasma On MPSK Singnal

When reentry vehicle enters the atmosphere in hypersonic speed, a plasma sheath will come into being on the surface of the vehicle because of high temperature, high pressure and friction with the atmosphere, which will seriously affect the normal operation of measurement, control and communication system. MPSK (Multiple Phase Shift Keying) modulation and demodulation system is simple, mature and widely used in aerospace TT&C area. The paper studies the impact of timing-varying plasma on MPSK signal.The paper introduces the characteristics of plasma sheath channel, including the basic principle of plasma and the influence of plasma sheath on electromagnetic wave. According to the simulation results of MPSK modulation and demodulation, pulse shaping, receive filtering and the auto gain control algorithms, a MPSK modulation and demodulation system based on the USRP2and GNU Radio software radio platform is developed. The system has the advantages of software radio. Using the system control UI can optionally select the system operating frequency, the modulation type and parameters, observe waveform diagram, spectrum, constellation diagram and eye diagram of the received signal in real-time. Through the MPSK modulation signal transmission experiment under the plasma sheath, the paper verifies the dispersion effect and modulation effect caused by the plasma sheath and studies the impact of timing-varying plasma on demodulation system.