Small-Signal Impedance of a Radio Frequency Plasma Capacitor

A capacitor for radio frequency control is proposed that uses a gas discharge plasma as a variable dielectric. Experimental small-signal impedance measurements on a prototype device at 500MHz-2.4GHz show a capacitance ratio of 2-6:1 with a quality factor of 60 at 600MHz. Results compare well with simple theoretical descriptions of the dielectric properties of plasmas.

I. Introduction

Radio Frequency (RF) control devices such as PIN diodes, RF microelectromecahnical systems (MEMS) and ferroelectric capacitors are becoming important in modern wireless communication systems. They are finding use in greater numbers in for example, adaptive antennas to increase system capacity and range through dynamic beam-forming [1]–[3]. Such applications dictate that the devices be capable of a high level of performance and flexibility at a low unit cost.