Quadrature hybrid coupler with two broadside coupled microstrip-slot lines

This paper presents the design of a quadrature hybrid coupler, which is comprised of two broadside connected microstrip lines. The fixed coupling is obtained by a rectangular slot in the common ground plane of these lines. This simple coupler's structure enables coupling higher than 3dB in a wide frequency band. Such a coupler can be used in a lot of applications, especially in antenna beam-forming networks, measuring systems, power amplifiers and complex microwave integrated circuits (MIC's) with crosswise lines.