Calibration and Use of a Reference Standard Directional Coupler for Measurement of Large Coupling Factors

Fixed frequency, point-by-point calibration is outlined for a reference standard directional coupler to be used in steppedfrequency measurement of 40-dB, or greater, coupling factors of directional couplers. If a reference directional coupler has a 40-dB coupling factor, a main-line waveguide output, and a sexless coaxial side-arm output, the best accuracy obtainable in measurement of its coupling factor is estimated to be ±0.03 dB.