Absolute loss measurement of highly reflective samples by using a high Q Gaussian beam open resonator at short millimeter wave frequencies

A high Q Gaussian beam open resonator and a new arrangement of it are described as a new method for determining absolute loss due to surface resistance of highly reflective materials at short millimeter- and submillimeter wave frequencies. The Gaussian beam open resonator consists of a pair of spherical mirrors with highly reflective partially transparent circular coupling regions and a plane minor, where the plane minor is the test sample. Application of this new method to reflection type measurement enabled simultaneous attainment of high Q factor and high signal-to-noise ratio, which would have been impossible using a conventional reflection-type open resonator with a small coupling hole. Moreover, the use of a pair of identical spherical mirrors enabled direct measurement of the Q of these mirrors, which is equal to Q/sub others/, without changing the experimental conditions. Surface loss measurements of metal films are made at 100 GHz band. In the room temperature experiment, surface resistance of 110 m/spl Omega/ was measured with an accuracy of /spl plusmn/7.6%.<>