Radar cross-section reduction by tunable low-pressure gas discharge plasma

In this experimental research, the effect of tunable low-pressure gas discharge plasma was examined on radar cross-section (RCS) reduction. A quintet array of plasma tubes (P _Ar = 10 torr, P _Hg ≈ 2–6 × 10⁻³ torr, R _in = 18 mm) next to each other was used to reduce the RCS of a planar metallic target. Plasma columns were optimized to have minimum axial and temporal inhomogeneity. The plasma electron density, plasma frequency, and collision frequency of the plasma tubes were measured by fast time-resolved microwave interferometry with simultaneous measurement of current and voltage. The influence of the discharge current (I _rms = 50–1500 mA) as a regulator of the plasma parameters was investigated. RCS reduction changes were observed by tuning plasma parameters at a frequency range of 2–18 GHz for the normal and oblique incidence of TE and TM polarizations. The assembled plasma tubes depicted broadband RCS reduction (<−10 dB) in TM polarization for a 300 mA discharge current (42.5% total bandwidth) and in TE polarization for a 1400 mA discharge current (34% total bandwidth) for normal incidence. It was shown that the measurement is in good agreement with the simulation. It was concluded that by performing bistatic measurements, the plasma cylinders behave as a wave absorber and scattering object in the TE and TM polarizations, respectively. (paper)