A 26- to 40-GHz fast-acting plasma waveguide switch

A fast-acting broad-band plasma waveguide switch has been developed which provides greater than 60-dB isolation and less than 0.25-dB cold loss over the 26-to 40-GHz frequency range. Switching times are under 200 ns, and the actuating trigger signal is a 150-volt 0.5-µs pulse from a high-impedance source. Geometrical enhancement of plasma density by employing metallic convergence cones is used. This technique provides a moderately ionized plasma from a beam whose strength would normally provide only a weakly ionized plasma in the absence of the convergence cone. A computer program of the transmission equation using a plasma slab model yielded the average plasma density and slab thickness in the waveguide; electric probes were used to detect electron temperatures along the cone axis.