Design of CPW Lange Couplers in Multi-Layer Thin-Film MCM-D

Three procedures (method of Ou, Paolino and Kajfez) for the design of CPW Lange couplers are compared for the first time. For each method, the couplers geometry is determined using a quasi-TEM program and verified by full electromagnetic simulations. The couplers are finally fabricated in a multilayer thin-film MCM-D process. The method of Paolino gives the best results. In the 10.8-14.9 GHz band, we have obtained a return loss below -18 dB, isolation below -20 dB, an amplitude balance below 0.2 dB and a phase balance of (90.7+/-0.9) deg. An excellent correspondence between measurement and simulations has been obtained.