Coupling and Impedance Between Line and Ground Electrodes on GaAs ; Implications for MMIC Design

Addressing the need for quantitative design rules in C.A.D. of microwave GaAs i.c.s, we describe the evaluation of microwave coupling and impedance for various systems of conductors on GaAs substrates. In particular, the coupling between two parallel microstrip lines has been calculated as a function of the presence of an intermediate screening electrode. Measurements. of the effect support the calculated data, and confirm a substantially reduced coupling across the electrode when grounded. The impedance of a line on a back-metallised substrate, with a parallel coplanar ground electrode has also been determined for a range of line geometries.