Synthesis of LTCC multi-band bandpass filter using reflection and transmission zeros

In this paper, a multi-band bandpass filter (BPF) based on a novel architecture and design method is presented. Very uniquely, its multi-band frequency response is synthesized by giving the transmission- and reflection-zero frequencies. To verify the proposed method, a miniaturized dual-band BPF is implemented using low-temperature co-fired ceramic (LTCC) technology. The size of filter is 2.0 mm × 1.25 mm × 1.0 mm with the two passbands at 2.4-2.5 GHz and 5.15-5.35 GHz for WLAN applications. Comparison of the filter S-parameters obtained by the synthesized prototype circuit, post-layout simulation and measurement shows good correlation.