Ali Kursad Gorur

Design of microstrip bandstop filter with adjustable wide passband using folded open-circuited stub resonators

This paper presents a new class of microstrip bandstop resonator filters. The folded open-circuited stub resonator located into microstrip loop structure is investigated using full-wave electromagnetic simulations. The utilization of the novel stub resonator allows a compact bandstop filter configuration to be realized. The proposed filter not only has a compact size, but also has a wider upper passband. Both simulated and measured results are presented to demonstrate the proposed filter.

Asymmetric response dual-mode dual-band bandstop filters having simple and understandable topology

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.

Design and analysis of a compact dual-mode dual-band microstrip bandpass filter

Design and fabrication of compact dual-mode dual-band microstrip bandpass filters with a novel feed scheme is presented. The proposed filters have two square loop resonators for two passbands, and each resonator is fed by the feedlines located at the upper corners of the resonators. By using the perturbation elements such as patches or corner-cuts, two degenerate modes of each passband can be easily excited, so mode frequencies and transmission zeros of the passbands can be controlled independently. Also, the proposed feed scheme provides the harmonic suppression for the first passband. In addition, theoretical results have been obtained by using an equivalent circuit model, and a coupling scheme is also presented. The designed filters have an electrical length of for the quarter wavelength resonator, where is the guided wavelength at 1.8 GHz. Two bandpass filters having elliptical and linear phase filtering characteristics in each passband have been designed, fabricated, and tested. Measured results are in an excellent agreement with simulated and calculated ones. In all frequency responses, return losses are better than 15 dB and insertion losses are at acceptable values for both passbands.

Quad-Band Microstrip Bandstop Filter Design Using Dual-Mode Open Loop Resonators Having Thin Film Capacitors

This letter presents a quad-band microstrip bandstop filter based on open loop resonators having thin film chip capacitors. For this purpose, dual-mode properties of open loop resonators are used and four independently controllable resonance frequencies are obtained by two open loop resonators in different electrical length. Even/odd mode analysis of the proposed structure is introduced to clarify the design method. In order to obtain higher degree, two unit cells including two resonators are used. While center frequencies can be independently controlled, the same is not true for the bandwidths and rejection levels. The proposed filter was also fabricated for the experimental verification of the predicted results. Four stopbands at 1.46, 1.86, 2.3 and 2.79 GHz were obtained in a good agreement with the predicted results.

A novel compact quad-band microstrip bandstop filter design using open-circuited stubs

A novel compact quad-band microstrip bandstop filter design is presented. Input and output ports of the filter are connected with a high impedance transmission line. Proposed filter is designed by using open-circuited stubs attached to the input and output ports. Thus, based on the fr - 3fr harmonic property of the stub-loaded resonators, four stopbands at 1.15-2.22, 2.94-4.56, 4.95-6.98 and 8.26-8.96 GHz are obtained. Insertion losses of all stopbands are better than 15 dB inside the stopbands. Under the even and odd mode excitations, resonance conditions of the structure are also investigated. For the experimental verification of the simulated results, proposed filter has been fabricated. Simulated and measured results are in a good agreement.

A novel compact triple-mode microstrip bandstop filter with adjustable reflection zeros

In this letter, the effect of open-circuited stubs on the frequency response of a microstrip square loop resonator shaped as a meander form is investigated with a full-wave electromagnetic (EM) simulator and a triple-mode microstrip bandstop filter is designed by using this effect. Proposed filter configuration is consisted of a microstrip square loop resonator shaped meander and four open-circuited stubs vertically and horizontally located inside the resonator. These stubs not only can be used to adjust the reflection poles in the stopband, but also used to obtain the miniaturisation. Central reflection pole is related with the horizontally located stubs, whereas the other two reflection poles are obtained from the vertically located stubs. In addition, the proposed configuration allows the controlling of the reflection zeros by changing the lengths of the stubs. Designed filter is simulated, fabricated and tested. Measured results show a good agreement with the simulated results.

Electronically switchable compact quad-band microstrip bandpass filter using varactor perturbed dual-mode resonators

Abstract In this paper, an electronically switchable quad-band microstrip bandpass filter is designed using varactor perturbed dual-mode resonators. For this purpose, four meandered dual-mode square loop resonators (DMSLRs) having reference patches are nested and varactor diodes are used to serve as perturbation elements. The designed resonator is analyzed by deriving even/odd mode resonance conditions. S-parameters are also calculated according to the even and odd mode input impedances. Stub loaded feedlines are used to couple the DMSLRs to Input/Output (I/O) ports. According to the capacitances of varactor diodes, each passband can be independently turned on and off. Coupling scheme and coupling matrix of the designed filter are introduced to realize the coupling descriptions. Switching operations are also investigated over the frequency responses obtained from coupling matrix. Passbands of the filter are adjusted to 1.4, 1.7, 2.25, and 2.7 GHz. The designed filter was also fabricated and measured results show a good agreement with the simulated and theoretical results.

Design of dual-mode dual-band bandpass filter with independently tunable bandwidths and reconfigurable filtering characteristics

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.

A novel microstrip diplexer design with tunable bandwidths and switchable channels for 4.5G applications

In this paper, a novel microstrip diplexer with tunable bandwidths and switchable channels is presented by using dual-mode square loop resonators (DMSLRs). Two resonators at different electrical lengths are coupled to input and output ports with lumped capacitors, and the isolation between the output ports is optimized by means of these capacitors. In order to obtain tunable bandwidth in each channel, varactor diodes are located at the orthogonal corners of the proposed resonators. In addition, the proposed resonators have reference patch elements at the lateral arms to provide convenience of varactor diode capacitances, such as perturbation elements. Depending on the capacitances of the varactor diodes, the bandwidths of each channel can be tuned. Furthermore, each channel can be switched off. The designed diplexer has two channels at the center frequencies of 1.8 and 2.6 GHz, which are allocated to 4.5G applications. Three-dB bandwidths can be tuned between 60 and 160 MHz for the first channel and between 150 and 350 MHz for the second channel. Isolation between the output ports is obtained as better than 18 dB in each channel. The designed diplexer was fabricated and measured, and the measured results were consistent with the predicted results.

Design of dual-mode substrate integrated waveguide filter using inductive slots

This paper presents a single-cavity dual-mode bandpass filter design based on a substrate integrated waveguide (SIW) resonator. The proposed resonator has various types of inductive loading, such as symmetrical/asymmetrical, thin and narrow slots which are used to achieve a compact circuit size. The presented structure has also a new perturbation arrangement for dual-mode SIW resonators depending on the movement of narrow slots. The designed structure is fabricated for the experimental verification of the proposed model. According to measured results, center frequency is obtained at 5.1GHz with a fractional bandwidth of %4.5. The measured insertion and in-band return losses are about −1.24 dB and about −15.4 dB, respectively. Measured results show a good agreement with the simulated results.