Optimization of miniaturized single- and multiband CPW-based matching transformers for RF circuitry on LCP substrates

We propose a novel approach to design compact coplanar waveguide (CPW) transformers to match predefined source and load impedances at single- and multi-frequency bands. The proposed transformers are optimized for the implementation on flexible liquid crystal polymer (LCP) substrates. The signal trace and the adjacent ground planes in the conventional CPW structure are width-modulated along the propagation path of the electromagnetic wave while maintaining a constant ground-trace separation. Validation is carried out by designing and simulating several matching transformers at different frequency bands. Specifically, single-, multi-, and wideband transformers operating at 1 GH, 0.9, 3.6, 5.4 GHz, and 1–3 GHz, respectively, are designed. Full-wave simulation results verify the proposed design procedure.