Abstract-This paper presents a novel approach for designing planar multimode wideband bandpass filters with good selectivity. The multimode resonator is composed of an open-ended microstrip line with length of half-wavelength (λ/2) and several radial-line stubs. By using different kinds of radial-line loaded stubs, different kinds of responses including three-pole and four-pole bandpass filters can be realized. Depending on electric field distribution and equivalent circuit model, the characteristics of the filter are analyzed. To verify the proposed method, two filters are implemented. The measured results exhibit good agreement with the simulation.

Abstract-A novel triple-mode hexagonal bandpass filter with capacitive loading stubs is introduced in this article. The technique, adding an open capacitive stub, is applied to enlarge the equivalent selfcapacitance of the resonator, which declines its resonant frequencies. Three radial-line stubs in the center of top layer are used to implement this technique. One mode resonant frequency is varied with the radii of three radial-line stubs, while the other two modes are nearly not affected. This filter has a pair of transmission zeros which are close to the passband, thus it behaves with high selectivity. For method validation, a bandpass filter operating at 2.4 GHz is fabricated and measured. The experimental results are demonstrated and discussed.

This letter presents two ultra‐wideband (UWB) antennas with 3.4/5.5 GHz dual‐notched bands. The U‐ and V‐slots are used to reject the frequency band (3.3–4.2 GHz) limited by C‐band satellite communication and Wimax systems. Another rejection band (5.15–5.825 GHz), limited by IEEE 802.11b or HIPERLAN/2 system, is obtained by using the U/V‐slot defected ground structure. Experimental results indicate that these antennas cover the entire UWB for voltage standing wave radio <2, except two notched bands. Moreover, these antennas have omnidirectional radiation patterns in the H‐plane and good gain flatness. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2942–2945, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24792

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A compact microstrip triple-mode bandpass filter using half-wavelength (k/2) open-ended microstrip line with double center loaded stubs is proposed in this article. By introducing a radial-line stub to the traditional dual-mode resonator, a triple-mode resonator is realized and the mode characteristics of the resonator are discussed. Also, an equivalent lumped circuit is proposed and the method of parameters extracting is given. The proposed filter exhibits a quasielliptic function response with a compact circuit dimension. At last, an experimental filter is fabricated and a good agreement between simulations and measurements is reached.