A first practical model of very small and low insertion loss laminated duplexer using LTCC suitable for W-CDMA portable telephones

A laminated duplexer using Low Temperature Co-fired Ceramics (LTCC) has been developed for the first time practically. The technologies of reducing the insertion loss are explained. They include the new ceramic-lamination process and the filter circuit design. The inner electrodes for the resonators are thicken by the state-of-art ceramic lamination process. The design of a laminated band elimination filter is also studied. As the result, its size is reduced by 30% comparing to a conventional mono block duplexer, while the performances are almost the same. It is very suitable for the next generation W-CDMA portable telephones.