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In this letter, a novel compact tri-band bandpass filter (BPF) with high selectivity is presented. The proposed tri-band performance measure is realized by using eight sets of resonators, i.e., two- and three-section stepped impedance resonators (SIRs). The three-section SIR is designed for determining the three passbands and providing the electric coupling, while the two-section SIR is used for determining each passband respectively and providing the magnetic coupling. Then, coupling structures with two transmission zeros near each passband edge are presented, therefore, the band selectivity of the filter is much improved. The three passband frequencies could be independently designed and tuned. This novel tri-band BPF is fabricated and the measured results are in good agreement with the full-wave simulation results. [ABSTRACT FROM AUTHOR]

A dual-band substrate integrated waveguide (SIW) filter is presented in this article. The dual-band cross-coupled design procedure is based on the frequency transformation from the normalized frequency domain to the actual frequency domain, which can calculate the coupling coefficients and the external quality factors analytically. The cross-coupled SIW filter has the flexibility to achieve different kinds of filtering characteristics with the same coupling structure. To validate the method, a practical SIW dual-band filter operating at 5.85-5.95 GHz and 6.05-6.15 GHz is designed and fabricated. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1609-1612, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26908 [ABSTRACT FROM AUTHOR]

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 novel dual-band filter using open loop ring resonator (OLRR) and defected stepped impedance resonator (DSIR) is presented in this paper. The OLRR forms one pass on the upper plane, and the DSIR forms the other pass on the lower plane. A proper designed feed structure is analyzed and used, which can provide desired external couplings to the two passes independently. At last, a dual-band filter with cascaded quadruplet (CQ) topology is designed and fabricated, which operates at WLAN bands 2.45/5.25 GHz. The simulated and measured results show good agreements and validate the proposed design method. [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 dual-mode bandpass filter based on conventional triangular structure is designed in this paper. The filter has the characteristics of compact structure, low insertion loss and so on. Several attenuation poles in the stopband are realized to improve the selectivity of the proposed bandpass filter. The experimented results were in good agreement with simulated results. [ABSTRACT FROM AUTHOR]

A novel bandpass filter with two dual-mode cavities based on the substrate integrated waveguide (SIW) is presented. By making use of the inductive discontinuities in an SIW cavity, two degenerate modes can be excited. Due to the phase difference of the two modes in each cavity, two transmission zeros on each side of the passband are created, so the out-of-band rejection of the filter is significantly improved. An SIW dual-mode filter with a center frequency of 12 GHz has been fabricated and measured. The experimental results agree well with the simulation results. [ABSTRACT FROM AUTHOR]

A novel dual-mode dual-band bandpass filter using meander-loop resonators is proposed in this letter. Different meander-loop resonators are operated for respective passbands. Several finite attenuation poles in stopbands are realized to improve the selectivity of the proposed bandpass filter and isolation between the two passbands. Compact size, dual band and high selectivity characteristics are realized by this type of filter structure. The filter is evaluated by experiment and simulation with very good agreement. [ABSTRACT FROM AUTHOR]

This paper presents a novel dual-band banpass filter using microstrip open-loop resonators. A new microstrip unit of dual-band bandpass filter is introduced, which can be used as unit element of duan-band filter design. The two open-loop resonators are treated as passband resonator and stopband resonator in analysis, respectively. A five-pole C-band dual-band bandpsss filter has been designed and fabricated. The measured results show a good agreement with the simulated results. [ABSTRACT FROM AUTHOR]

A novel design method of dual-band and tri-band band-pass filters is proposed in this paper. A compact loaded open-loop resonator(LOLR) structure is introduced. The resonant frequency response of the resonator is described in detail. A dual-band filter and a tri-band filter are designed with the LOLRs. 0° feed structures are applied to improve the selectivity of the proposed filters. The measurements of the filters are in good agreement with the simulated results. [ABSTRACT FROM AUTHOR]

A design method of tubular filter based on S-parameter curve-fitting method is presented, and a synthesis process from low-pass prototype to tubular band-pass filter is also analyzed. By using step-increasing theory, the curve-fitting process for designing tubular filter is proposed in particular. This method not only makes sure that the values of serial elements are accurate in each simulated process, but also reduces the factors which influence the values of shunted elements, and decreases the complexity in determining the element size. [ABSTRACT FROM AUTHOR]

A compact dual-band bandpass filter using folded tri-section stepped impedance resonators (FTSIRs) is proposed in this article. Resonance characteristics of the tri-section stepped impedance resonator (TSIR) are derived and described in detail. A cross-coupled dual-band filter for WLAN(2.4/5.2 GHz) is designed with four FTSIRs. The measurement of the filter is in good agreement with the simulation. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 407–409, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23110 [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]

A topology of a compact planar microstrip filter with a notched band is introduced, which employs a split-ring resonator defected ground structure (DSRR). Folded short-circuited stubs are used to realise the bandpass filter with good selectivity and out-of-band characteristics. By employing a split-ring resonator defected ground structure, a narrow notched band was introduced to reject the undesired wireless local-area network (WLAN) radio signals. 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 0.5 ns throughout most of the two passbands. The width of the narrow notched band is about 1 GHz and the attenuation is more than 25 dB at the centre frequency of 5.4 GHz. [ABSTRACT FROM AUTHOR]