Attenuation of electromagnetic waves by plasma-covered cavity

Among the various contributors to the Radar Cross Section (RCS), measurements have shown that the cavity structure have a very significant impact on the overall signature of the airplane structure1,2. We have simulated the real-time status of the electromagnetic (EM) scattering by the plasma-covered metal cavity, using the finite-difference time-domain (FDTD) method. The results show EM attenuation is significant by applying plasma to the cavity structure because of the multiple interactions between the EM wave and the inner surface of the cavity. When the EM wave hits the cavity at the front aspect angle, the signals propagate along the central axis of the cavity and the returning waves converge to source for all incident frequencies. On the contrary, when the EM wave hits the cavity at the oblique aspect angle, the combine of reflected waves among the inner walls of the cavity will result in constructive or destructive interference, consequently the returning wave not converging to source any more. The values of peak return loss are extremely different between plasma-covered metal plate and plasma-covered metal cavity. A plasma reactor, filled with argon gas at low pressure, driven by a Radio-Frequency power source, was produced. The measured result has a similar development with simulation.