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This paper presents a novel approach for designing planar triple-mode bandpass filters with good selectivity. The proposed triple-mode resonator is developed from traditional dual-mode stub-loaded resonator, and it is composed of a section of half-wavelength (λ/2) open-ended microstrip line and a pair of open-ended stubs. The field patterns of the three modes associated with theoretical analysis are investigated. By modifying the proposed triple-mode filter, a compact triple-mode bandpass with several transmission zeros in stopband is realized. The controllable transmission zeros provide a good selectivity to the filter. An experimental filter is fabricated, and both the simulated and measured results are presented. [ABSTRACT FROM AUTHOR]

In this paper, two hexagonal meander loop resonators with circular patches and their applications to filters are presented. Only one mode characteristic has been affected by changing the size of the circular patch, which is different from the conventional meander loop resonators. Compact size, low loss and high selectivity characteristics are realized by the filters using this type of resonators. Two filters are designed, fabricated and measured. The measured results exhibit good agreement with the simulated ones. [ABSTRACT FROM AUTHOR]

This paper presents a dual-mode dual-band microstrip bandpass filter based on an open-loop resonant structure. By introducing a square notch and slots in the resonator, one of the passband can be controlled easily. Several finite transmission zeros are realized to improve the selectivity of the proposed dual-band filter and the isolation between the two passbands. To verify the proposed filter, an experimental filter is implemented. Both the simulated and measured results are presented. [ABSTRACT FROM AUTHOR]

A peach-like ultra-wideband (UWB) planar monopole antenna (PMA) with dual stopband characteristic is presented in this paper. It is designed to work on a substrate Rogers RT5880 that has a thickness of 1 mm and relative permittivity of 2.65. The proposed antenna is fed by microstrip line; the U-slot is used to reject the frequency band (3.3–4.2 GHz) limited by IEEE 802.11a or HIPERLAN/2. Another rejection band (5.15–5.825 GHz) limited by IEEE 802.11b and C-band satellite communication systems is obtained by using the V-slot defected ground structure (DGS). The size of the antenna is 33 mm × 35 mm. Effects of varying the interior degree of the V-slot DGS and the length of the U-slot on antenna performance have also been studied. Measured result shows the designed antenna with an impedance bandwidth covering at least 3.11 to 15 GHz assuming a 10 dB return loss, except 5.04–6.42 GHz and 3.35–4.24 GHz band. Also the simulated results show that the antenna has omnidirectional radiation patterns in the x-z plane and good gain flatness. [ABSTRACT FROM AUTHOR]

A coplanar waveguide (CPW) fed diamond monopole antenna with dual stopband characteristic is presented in this paper. The proposed antenna consists of a circular CPW feeding line and a diamond shape radiation patch. By using a U-slot in the feeding line, a stopband of 800 MHz for band rejection of wireless local area network (WLAN) is achieved. Another stopband of 600 MHz is obtained by implanting two slits in the ground plane. Experimental results show the designed antenna, with a compact size of 40 mm × 25.8 mm, has an impedance bandwidth of 3.2–10.7 GHz for voltage standing wave radio (VSWR) less than 2, except two frequency stopbands of 3.4–4.3 GHz and 5.1–5.9 GHz. Moreover, the antenna also shows omnidirectional radiation patterns in the H-lane and good gain flatness. [ABSTRACT FROM AUTHOR]

A microstrip bandpass filter implemented with slow-wave open-loop resonators is described in this letter. The slow-wave open-loop resonators make the filter compact and allow implementation of positive and negative inter-resonator couplings. Implementation of the positive and negative couplings is used to introduce a pair of finite frequency transmission-zeros in the filter response. The two zeros are designed to be close to the passband, thus improving the selectivity of the filter. As an example, a quasi-elliptic filter is fabricated. The quasi-elliptic filter has a compact dimension of 22.1 mm × 21.16 mm, which is approximately 0.1705λg × 0.1634λg. The experimental results are demonstrated and discussed. [ABSTRACT FROM AUTHOR]