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We present here a novel pattern with compact size of ultra-wide band microstrip filter. The filter is originally modeled from five poles quarter-wavelength short-circuited stubs. It is then, transformed into a new compact butterfly-like pattern. This new “butterfly-shaped” pattern consists of three vias instead of five vias from its original design. The prototype has shown an improvement in scattering parameters measurement compared with its original model. It delivers 112% of fractional bandwidth, magnitude of insertion loss better than 1.6 dB and return loss lower than -8 dB. It is fabricated on RT Duroid 5880 with 2.2 dielectric constant, 0.508 mm of substrate thickness and 35 μm copper thickness. The overall dimension of the filter is 20.7 × 15.8 mm2. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2116–2119, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24568 [ABSTRACT FROM AUTHOR]

A quad-band bandpass filter (BPF) employing a sextuple-mode and a dual-mode stub loaded resonator are presented in this paper. The proposed sextuple-mode resonator generates the first, second and the fourth passband while the third passband is achieved by the dual-mode open stub-loaded resonator. The proposed sextuple-mode resonator modified from quintuple-mode resonator produces five resonant modes while the sixth-mode is generated by the coupling of the open ends of two stub resonators. Based on the odd- and even-mode analysis of the sextuple-mode resonator, the odd- and even-mode resonant frequencies can be flexibly controlled by tuning the corresponding resonator dimensions. Subsequently, the proposed sextuple resonator is combined with dual-mode open stub loaded resonator to achieve the quad-band BPF, centered at 1.75/2.45/3.50/5.25 GHz. The size of filter is about 0.13 λ g × 0.22 λ g , where λ g is guided wavelength on the substrate at 1.75 GHz. The measured results agree well with the simulated results. [ABSTRACT FROM AUTHOR]