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A compact ultra-wideband (UWB) bandpass filter (BPF) with simultaneous narrow notched band and out-of-band performance improvement is presented. The UWB BPF is built up using the hybrid microstrip and coplanar waveguide (CPW) structure. By employing the split-ring resonator (SRR) which is defected on the lower plane, the narrow notched band was introduced. The center and bandwidth of the notched band can be controlled by adjusting the length and width of the SRRs. A novel cross-shape patch is constructed to implement transmission stopband in the upper out-of-band so as to suppress the spurious passband. The novel UWB BPF is designed and fabricated. The measured insertion loss is less than 1.6 dB, the return loss is more than 13 dB and the variation of group delay is less than 0.12 ns. The width of narrow notched band is about 0.15 GHz and the attenuation is 18 dB at the center frequency of 5.76 GHz. The upper stopband is up to 15.2 GHz with rejection greater than 20 dB. [ABSTRACT FROM AUTHOR]

A wideband cross coupled bandpass filter making use of square split-ring resonator (SRR) defected ground structure (DGS) and parallel microstrip feed line is presented in this paper. The coupling between a pair of SRR DGS is much larger than that of the conventional SRR, which is fully investigated and applied to the design of wideband cross coupled filter. By extracting the coupling coefficient of various coupling structures and external quality factors of various feed structures, a SRR DGS four-pole filter with center frequency of 2.2 GHz and bandwidth of 20% is designed and fabricated. [ABSTRACT FROM AUTHOR]

A novel type of dual-band microstrip structure and its equivalent circuit are investigated, which is composed of defected split-ring resonator and interdigital capacitor. The influence of design parameters on the frequency characteristics is discussed, then a dual-band microstrip filter, which has two passbands of 1.8–2.5 GHz and 5.5–5.9 GHz with a transmission zero, is designed and fabricated. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2104–2106, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22673 [ABSTRACT FROM AUTHOR]

A tri-band bandpass filter (BPF) using a novel square ring loaded resonator (SRLR) is presented. The SRLR can generate a tri-band response by tuning its geometric parameters. Moreover, it can build the high-order tri-band BPFs using the proposed resonators because of the sufficient coupling between adjacent resonators. A fourth-order Chebyshev tri-band BPF centred at 2.4, 3.5 and 5.2 GHz is designed and fabricated. Measurement results agree well with the full-wave EM simulated results. [ABSTRACT FROM AUTHOR]