Comparison between metal wire grid and plasma wire grid

Summary form only given. Metal wire grids has been used as polarizer in microwave and optical systems, as the spacing between wires d becomes smaller than the wavelength λ, the extinguish ratio between two polarization becomes large. In this experiment, the metal wire grid is replaced by Cold Cathode Florence Light (CCFL) tubes arranged in a tight formation, and the spacing between tube s is around 8 mm. Several metal wire grids of similar spacing are also constructed. Both kinds of grids are placed in an anechoic chamber and transmission measurements were conducted with a network analyzer.We found that even for metal wire grids, the S₁₂ measurement s differ considerably from the early theories [1,2]. For V-V-V polarization, deepest attenuation happens around 1 GHz at about -40 dB, and the next significant attenuation happens around 4 GHz when the spacing is changed from 12 mm to 8 mm. Overall, the transmission fluctuates around 10 dB. For metal wire grid V-H-V polarization, there is no low frequency cutof f, but overall fluctuations increase. For the plasma wire grids, the general behavior behaves more like metal wire grids in V-H-V polarizations, there is no low frequency cutoff, and thee are enhancements of transmission at certain frequencies as high as 12 dB. These measurements suggests: a) the conductivity of the plasma is much lower than theory, b) The microscopic random motion of electrons in the plasma renders the macroscopic direction of the plasma tubes irrelevant, c) Enhancement in trans mission are caused by resonance from plasma.