Broad Bandwidth Microwave Measurements of Materials Using Photoconductively-Pulsed Antennas

Abstract

Accurate measurement of the microwave dielectric properties of materials is an important issue because of the continued advances in high-speed electronic and optoelectronic devices. In packaging conventional electronics, materials such as polymers or ceramics are used as dielectric interlayer spacers. The complex microwave dielectric properties of these surrounding media determine the delay, attenuation, and dispersion of fast electrical signals between devices. Because at present the fastest electrical devices have risetimes of less than 10 picoseconds,1 it is important to be able to measure the properties of dielectric packaging materials to frequencies greater than 100 GHz. Similarly a knowledge of the dielectric properties of polymers and crystalline materials are required in optoelectronics because these materials are being used in high-speed electro-optic modulators and switches. The optical response of these materials is generally very fast so that the ultimate performance of the electro-optic device is determined by the switching time which depends on the capacitative time constant and the microwave group velocity.2