A wide-band directional coupler for time-domain measurements

Describes the design, construction, and testing of a broadside parallel-line directional coupler for 0.4 to 10 GHz. The coupler was built to obtain larger reflected signal levels in the time-domain measurement of well-matched microwave components. It features a 10.75 in (27.3 cm.) tightly coupled uniform parallel-line region to keep internal reflections out of the 2.5-ns measurement time window. Using a 6-V impulse generator the coupler produced a 5.4-dB improvement in reflected amplitude over the usual reflectometry configuration. A major use for the coupler has been in simultaneous measurements of S₁₁ and S₂₁ scattering parameters.