A novel dual-mode double square loop resonator (DMD-SLR) for dual-band band-pass filter (BPF) is presented in this paper. The simple meander loop in DMDSLR is studied to improve the performance of the conventional DMDSLR. Significant size reductions over 33% are achieved. In addition, the designed meander-loop DMDSLR filter shows lower insertion loss (2.24 and 2.28 dB), higher rejection level (28/56 dB and 53/36 dB), wider bandwidth (about 8.5% and 28%) at the 2.47 and 5.47 GHz bands, respectively. Two transmission zeros are placed between the two pass-bands and result in a good isolation.

The CPW‐fed configurations of dual‐mode double‐ring resonator (DMDRR) and double‐square‐loop (DMDSLR) are introduced to achieve the performance of the dual‐band filters. To obtain lower insertion loss, higher out‐of‐band rejection level, and wider band of DMDRR and DMDSLR filters, using two twin‐T couples and dual‐mode perturbations are proposed here. Simulation and measurement results including surface current distributions and frequency responses are presented and discussed. It can be applied to 0.9 and 1.2 GHz dual‐band systems. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2010–2015, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24574