High-frequency wave measurement substrate

Abstract

A high frequency wave measurement substrate comprising a dielectric substrate, a ground conductor being formed almost all over a bottom surface of the dielectric substrate, a microstrip line signal conductor and an radial stub-like equivalent ground conductor which is placed in proximity to an end of the microstrip line signal conductor being formed on a top surface of the dielectric substrate, a coplanar line structure wafer probe signal conductor and a ground conductor being electrically connected to both the signal conductor and the equivalent ground conductor, wherein the equivalent ground conductor is composed of a semi-circular or fan-shaped radial stub-like conductor pattern in which non-conductor areas are formed in its radial direction. The equivalent ground conductor is also composed of a plurality of radial conductors which are sharing a center with each other, disposed like an arc, and different from each other in length in the radial direction, and a connecting conductor for electrically connecting the radial conductors to each other electrically. In the high-frequency wave measurement substrate a product of a thickness h of the substrate and a square root of a relative dielectric constant &egr;,of the substrate is set to be,or more and,or less of a vacuum wavelength &lgr;,of a measurement upper limit frequency. Consequently, the standing charge density distribution in the circumferential direction is caused by lower frequencies, so that the low loss transmission frequency band can be expanded.