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In this letter, a dual-mode dual-band microstrip bandpass filter design with center frequency control methodology is presented by using dual-mode meandered loop resonator. Center frequencies of the passbands can be controlled by changing the connection points of internally located square loop loading elements without changing the total surface area. These loading elements are also useful to obtain a compact configuration. In addition, while the first passband has two reflection zeros, the second passband has one reflection zero, as it is obtained from the harmonic of the first passband. Therefore, degenerate modes of the first passband can be excited by a perturbation element. Using patch or corner cut perturbation elements, elliptical and linear phase filtering characteristics can be obtained in the first passband, respectively. Two dual-mode microstrip bandpass filters having elliptical and linear phase filtering characteristics were designed, fabricated, and measured. Measured results are in a very good agreement with the simulated results. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:639–642, 2015

In this paper, design of a tunable dual-mode dualband microstrip bandpass filter is presented. The designed filter is constructed by using two nested dual-mode resonators (DMRs) having two patch capacitances located at the lateral arms of the resonators as reference elements. Varactor diodes are used instead of perturbation elements in order to excite the degenerate modes. Linear phase and quasi elliptical filtering characteristics can be independently obtained in each passband and the band-widths can also be tuned at both filtering characteristics. For the experimental verification of the designed structure, a dual-mode dual-band microstrip bandpass filter was fabricated and measured. Center frequencies of the passbands were adjusted to 1.78-2.65 GHz and 1.83-2.7 GHz for linear phase and quasi elliptical filtering characteristics, respectively. Insertion losses in each passband were observed as better than 3 dB in measurements. © 2017 IEEE.

44th European Microwave Conference (EuMC) -- OCT 05-10, 2014 -- Rome, ITALY, WOS: 000392912200265, A new design of dual-mode bandstop filters with four poles employed by single dual-mode microstrip square loop resonators are proposed. Two fourth order filters with two pairs of reflection zeros at real or imaginary finite frequencies are demonstrated with simulations and measurements. It is shown that the location of reflection zeros and degenerated modes can be easily controlled by simply changing the perturbation element size. It is shown that one of fourth order filters has two finite-frequency reflection zeros on only left side of the stopband, while the other one has two pairs of finite-frequency reflection zeros in the lower and upper passbands. Good agreement between simulated and measured results is achieved., APS, European Microwave Assoc, IEEE MTT S, horizon house

43rd European Microwave Conference (EuMC) -- OCT 07-10, 2013 -- Nuremberg, GERMANY, WOS: 000330768700010, A novel microstrip dual-mode bandstop filter with Coplanar Waveguide (CPW) fed structure is proposed by using a microstrip square loop resonator. Two types of coupling between the degenerate modes are described by changing the perturbation's sizes as in conventional ones. The difference between the proposed filters and conventional ones is resonator fed structures. In the proposed filter design method, CPW-fed structure is used to excite the degenerate modes of the resonator with degenere modes of the square loop resonator. Finally, two dual-mode bandstop filters are designed and realized with using degenerate modes of the microstrip square loop. It is shown that the size of the perturbation element determines the location of the reflection zeros of the filter according to the coupling type of the resonator., APS

Asia Pacific Microwave Conference 2009 -- DEC 07-10, 2009 -- Singapore, SINGAPORE, WOS: 000279924300235, A novel simple and understandable topology is proposed for dual-mode dual-band bandstop filters with asymmetric frequency response. Two microstrip square loop resonators are used to obtain the dual-band filter characteristic. Each resonator uses a perturbation element to excite dual-modes. Distinct characteristics of new filters are investigated using full-wave electromagnetic simulations. It is also found that there are five reflection zeros. Three of them are inherently associated with the proposed topology, whereas the other reflection zeros near stopbands are associated with the perturbation. They may be easily adjusted by changing the size of the perturbation element. Four dual-band filters using dual-mode resonators are demonstrated with different asymmetric responses, which result from different locations of adjustable reflection zeros. Both simulated and measured results are presented and exhibit dual-mode dual-band bandstop responses with high sharpness., Scientific and Technological Research Council of Turkey (TUB TAK) [107E117]; Turkish Academy of Sciences (TUBA), This work was supported by the Scientific and Technological Research Council of Turkey (TUB TAK) under Grant 107E117 and Turkish Academy of Sciences (TUBA).