Tunable duplexer having multilayer structure using LTCC

A tunable duplexer has been designed for GSM1800/1900 digital cellular system. The tunable duplexer has been fabricated with LTCC (Low Temperature Co-fired Ceramics) multilayer technologies assisted by varactor diodes. To accomplish higher attenuation for each system, multi-tuning method, which enables to control the passband and the stopband independently, is applied. Size is designed as 5.7/spl times/5.7/spl times/1.8mm. Insertion losses are less than 3.5dB. Attenuation is more than 25dB at Fo+200MHz in Tx, and is more than 10dB at F0-150MHz in Rx.