Design of dual-band bandpass filters with controllable bandwidths using new mapping function

In this paper, a novel design method for a dual-band bandpass filter (BPF) with arbitrary controllable bandwidths based on a simple frequency mapping function is proposed and its analytical design equations are also derived. The circuit conversion techniques are employed for implementation with distributed transmission line. To validate the proposed dual-band BPF with controllable bandwidths, a low temperature co-fired ceramic (LTCC) transmission line as well as microstrip lines are used, respectively. The two types of design for the dual-band BPF have the same and significantly di®erent fractional bandwidths (FBWs), respectively. The first type of dual- band BPF with same FBWs are implemented at 2.11-2.17 and 3.45- 3.55 GHz. The second type of dual-band BPF with di®erent FBWs are implemented at 3.40-3.60 and 5.15-5.25 GHz. The measured and theoretical results show good agreement, significantly validating the proposed frequency mapping function methodology.