Theoretical Study on the Impacts of Plasmas Enveloping Reentry Vehicles on the Radiation Performance of Terahertz Array Antenna

Reentry vehicles used to be enveloped by weakly ionized plasmas. These plasmas could yield communication blackout, which is considered as a serious threat to reentry vehicles. In the recent couple of decades, the terahertz (THz) communication is considered to be a potential approach to mitigate the communication blackout. On the other hand, the electron density distribution surrounding a reentry vehicle is inhomogeneous. The dense and inhomogeneous free electron could make an impact on the THz onboard antenna. The present study investigated the radiation performance of a 0.14-THz phase array antenna in weakly ionized plasma layers. The present study shows that the antenna gain, lobe width, and the lobe direction are influenced by weakly ionized plasma. Further study showed that the antenna gain and the lobe width are impacted by both electron density and electron collision frequency. However, the lobe direction is influenced by the electron density only. The mechanics of such phenomena are analyzed. In addition, a concept of approach to compensate the worsened antenna performance with the beamforming technology is proposed. The simulation results showed that the approach compensates the shifted lobe direction well. Also, it helps improve the antenna gain in the expected direction.