Design of Microwave MCM-D CPW Quadrature Couplers and Power Dividers in X-, Ku- and Ka- band

The successful design and measurement of high-performance coplanar waveguide (CPW) quadrature hybrid couplers integrated in MCM-D at Ku and Ka-band and Wilkinson power dividers at X-band are discussed in this work. The authors have investigated the feasibility of integrating 3-dB quadrature couplers in the MCM-D technology. Quadrature couplers based on two edge-coupled lines are not practical, as the required line-dimensions are too small. As an alternative, couplers using re-entrant sections and CPW Lange couplers have been realized. For the Lange coupler, the authors have obtained in the 10.5-14.5 GHz band: a return loss and isolation better than 20 dB, an amplitude balance below 0.13 dB, and a phase balance of (90 +/1) deg. For the coupler using re-entrant sections, the researchers have obtained in the 20-30 GHz band: a return loss better than 17 dB, isolation better than 20 dB, an amplitude balance below 0.25 dB, and a phase-balance of (90 +/2.5) deg. A trade-off between these two design-approaches for integration in MCM-D is given. Distributed and lumped Wilkinson power-dividers at X-band have been designed using the in-house developped design library. An excellent agreement has been found up to 50 GHz.