High frequency breakdown characteristics of various electrode geometries in air

In airborne and spacecraft electronic applications, minimum weight and volume constraints have always influenced electrical component and cabling designs. Insulation system specifications must include the total operating environment, voltage excursions, current capacity, mechanical integrity and aging. This is true for both power source equipment as well as special purpose electronics such as radar or high power transmitters, where bare or insulated conductors are often used for high frequency signal transmission, as well as power transmission. A brief review of relevant data is presented to exemplify the effects of high frequency content on breakdown voltages in air, for specific electrode configurations. At high frequencies, the spacing between electrodes or conductors becomes a deterministic parameter for the breakdown phenomenon known as multipactor. When the mean free path of an electron exceeds the order of electrode spacing or relative dimension of the high frequency system, multipactor breakdown may occur, usually at pressures less than 10^-2 torr. Multipactor is prevalent within or around components of the high frequency system such as the waveguide, antenna, cabling, connectors and switches. Information that may be useful to designers of components and interconnections includes high frequency initiation phenomena and multipactor breakdown characteristics. Data concerning low pressure corona initiation on antennae is also presented