Calculation of combined stub directional couplers on microstrip and slot lines

The use of traditional microstrip couplers in microwave integrated circuits, where the problem of miniaturization is extremely important, is problematic. Transition to 3D-structures using combinations of the transmission lines provides both improved mass-dimensional parameters and the electrical characteristics of integrated circuits. The paper presents compact couplers on the base of a microstrip and slot line combination considering their implementation. Formulas for calculating of impedances of transmission line segments defining the structure of couplers are obtained. It is shown that the proposed schemes have better parameters than a traditional three-stab microstrip coupler.