An LTCC duplexer for GSM/DCS applications

A miniaturized quasi-lumped element multiplayer duplexer is designed and fabricated using a standard low-temperature co-fired ceramic (LTCC) technique for application of GSM/DCS communication system. Several transmission zeros are specially introduced to provide sharp slope sides and enhance the isolation between the lowpass and highpass channels. An additional transmission zero is located in the stopband of lowpass filter to improve the high frequency rejection. The expected superior performance is validated by the measured S-parameters, which are in good agreement with the simulated results. The duplexer has the advantages of compactness, high integration, and low cost.