Measurement techniques for studying the dielectric permittivity of lossy ceramic composites used in vacuum electronics

Improved techniques and specialized systems for performing measurements of the complex dielectric permittivity of ceramic materials from 26.5-40 GHz over the -185 to +250/spl deg/C temperature range have been developed. The methodology is intended primarily to measure the dielectric properties of lossy ceramics used in vacuum electronic devices, such as BeO-SiC and AlN-SiC. The elevated temperature studies are needed to ascertain how the dielectric properties will change over the conditions known to exist in high average power devices, while the low temperature capability is important for understanding the competing mechanisms of dielectric loss in the materials themselves. Although the present work has concentrated on Ka-Band, the techniques are general and can be replicated in other frequency ranges.