Design of mm-Wave Slow-Wave-Coupled Coplanar Waveguides

This article focuses on the design of high-performance coupled slow-wave coplanar waveguide (CS-CPW) in CMOS technologies for the millimeter-wave (mm-wave) frequency bands. First, the theory as well as the electrical model of the CS-CPW are presented. Next, the analytical approach for the calculation of the model parameters is discussed. Then, by using the developed model, two mm-wave backward directional 3-dB couplers are designed in a bipolar complementary metal-oxide-semiconductor (BiCMOS) 55-nm technology for 120- and 185-GHz operation, respectively. Simulation and experimental results demonstrate that the use of the CS-CPW concept leads to state-of-the-art performance, with a good agreement between the analytical model, electromagnetic simulations, and measurement results.