Design of Dual and Triple-Passband Filters Using Alternately Cascaded Multiband Resonators (original) (raw)
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A quad-mode resonator is proposed for novel design of dual-band bandpass filters (DBBPFs) with good selectivity and compact size. The symmetrical resonator consists of a pair of coupled line sections (CLSs) and a transmission line section (TLS). Odd-/even-mode method is used to clarify the mode characteristics. Four excited resonant modes are applied to produce two passbands. The frequency ratio range can be adjusted by the CLSs, and the bandwidths can be controlled by the TLS. After installing a pair of U-shape coupling arms, a DBBPF with five transmission zeros (s) around the two passbands are designed and fabricated. The measured results are in good agreement with the simulated results, demonstrating that the proposed filter is feasible in practical use.
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A quad-mode resonator is proposed for novel design of dual-band bandpass filters (DBBPFs) with good selectivity and compact size. The symmetrical resonator consists of a pair of coupled line sections (CLSs) and a transmission line section (TLS). Odd-/even-mode method is used to clarify the mode characteristics. Four excited resonant modes are applied to produce two passbands. The frequency ratio range can be adjusted by the CLSs, and the bandwidths can be controlled by the TLS. After installing a pair of U-shape coupling arms, a DBBPF with five transmission zeros (s) around the two passbands are designed and fabricated. The measured results are in good agreement with the simulated results, demonstrating that the proposed filter is feasible in practical use.
A dual-band bandpass filter with wide and highly attenuated stopbands is designed using parallel coupled microstrip line (PCML) and stepped-impedance-resonators (SIRs). The proposed filter is composed of a pair of highly coupled PCML-SIR structure and a central resonator using a low impedance rectangular microstrip. Initially, the wide dual-band performance is achieved by creating a transmission zero between those two bands using a tightly coupled PCML-SIR with a suitable impedance ratio. Then, a low impedance resonator is placed between the pair of PCML-SIR to generate multiple resonant frequencies for a broadband performance. The simulated and measured results of those filters agree very well. The bandwidth of the first band in the developed filters extends from 1.75 GHz to 3.75 GHz with less than 0.3 dB insertion loss at the center of the band. The second band has a bandwidth that extends from 6.95 GHz to 8.75 GHz with less than 0.5 dB insertion loss at the center of that band. The stopband separating those two passband has more than 30 dB attenuation with transmission zero at 5.85 GHz.
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This letter presents a compact tri-band bandpass filter (BPF) with controllable bandwidths. The proposed filter employs dual-mode resonators, i.e., crossed open-short stub loaded resonators and tri-section stepped impedance resonators. The center frequencies and bandwidths of the three passbands can be conveniently controlled by tuning the dimensions of two resonators. Moreover, on each side of each passband, there is at least one transmission zero, resulting in high skirt selectivity. To validate the design and analysis, a prototype of tri-band BPF is fabricated. Good agreement can be found between the measured and simulated results.
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A dual-band bandpass filter topology based on coupled-lines is presented. In the topology, two identical coupledlines are cascaded in series and duplicated in parallel. There are then ended with another two identical coupled-lines. The dualpath structure exhibits a 2 nd order dual-band response with three transmission zeros that separate the passbands from each other, and from the rejection band. The odd-and even-mode impedances of the coupled-lines control the bandwidth, passband and out-of-band responses of the dual-band filter. Finally, to verify the concept, a prototype of a dual-band bandpass filter is designed using EM simulator, fabricated on 1.6-mm-thick FR-4 substrate and measured. The resonant frequencies of the two passbands are centered at 1.82 GHz and 2.38 GHz.
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In this paper the design of a cross-coupled planar microwave band-pass filter using open-loop square microstrip resonators, with two symmetrically placed attenuation poles, is presented. The design starts from the following specifications: central frequency 3GHz, 150MHz bandwidth, 1dB ripple in the pass-band corresponding to return loss of 6.8dB.The adjustment method using additional ports placed on each resonator of the filter is used, allowing the interconnection of the filter structure with external lumped elements. Connecting a reactive element (capacitor) from such an additional port to ground allows a fine tuning of the resonator. Connecting a reactive element between two such additional ports allows a fine change in the coupling coefficient between these resonators. After adding four extra ports and connecting the external elements (capacitors), it is possible to use fast circuit simulation software to optimize the filter's response. Then all these capacitors have to be gradually eliminated, by compensating their effects through fine changes back in the layouts. If some specific issues are properly handled, this procedure improves considerably the quality of the final design of the filter. After a thorough optimization of the layout, the filter was fabricated and measured. The results of measurements are in good agreement with the specifications of the filter, showing this way the efficiency of the applied optimization method.