Development of 2GHz band micro LTCC duplexer by combining BPF and diplexer

Duplexers are commonly used in all mobile communication devices such as cellular phone. The typical duplexers used are expensive duplexers that use the semiconductor process such as SAW duplexer and FBAR. This study designed a low-priced duplexer using the LTCC lamination process. Generally, the duplexer filter built with LTCC (low-temperature co-fired ceramic) lamination process technology uses strip line resonator to construct the filter. This type of strip line structure shows poor quality factor(Q) compared to the currently used SAW duplexer or FBAR; hence the difficulty in constructing a duplexer with rapid skirt characteristic in narrow band with low loss. This study constructed a duplexer by combining a band pass filter and a diplexer to simplify the circuit and a 3×2.5×1.2 mm³ miniaturized 2GHz band duplexer. Also it can be embedded into the complicated MIMO FEM(Front end module).