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Öğe A high isolation quad-channel microstrip diplexer based on codirectional split ring resonators(Wiley, 2022) Gorur, Ali K.; Turkeli, Alper; Buyuktuna, Mert; Dogan, Engin; Karpuz, Ceyhun; Gorur, AdnanIn this study, a novel microstrip diplexer with four channels is designed by using codirectional split ring resonators (CDSRRs). Since CDSRRs provide dual resonance behavior, dual-band bandpass filter with two poles at each passband can be created by coupling identical CDSRRs to input/output ports. Based on this approach, quad-channel diplexer can be designed by coupling two more CDSRRs in different electrical length to another output. Both filters are fed by similar feeding lines. High isolation can be observed between the output ports by means of CDSRRs. The designed quad-channel microstrip diplexer was also fabricated and tested for experimental verifications. The measured results are in a good agreement with the simulated results. Center frequencies of the channels were measured at 2.12, 2.45, 3.90, and 4.48 GHz with the minimum insertion losses of 2.27, 2.88, 2.00, and 2.71 dB, respectively. Isolation was observed as better than 44 dB from DC to 6 GHz.Öğe A New and Simple Approach on Multi-Resonator Circuit Based Chipless RFID Tags for IoT Applications(IEEE, 2020) Dogan, Engin; Gorur, Ali Kursad; Karpuz, Ceyhun; Gorur, AdnanIn this paper, a novel multi-resonator circuit as a chipless RFID tag is proposed for internet of things (IoT) applications. For this purpose, a simple geometrical transition between a dual-mode square loop resonator (DMSLR) and an open loop resonator (OLR) is introduced by means of a small patch. Two frequency codes can be obtained from a DMSLR, since it has two resonance frequencies. On the other hand, while an OLR is utilized, only one frequency code can be obtained. Thus, totally 3 frequency codes can be achieved from one resonator in a very simple way and 3(N) codes can be achieved by using N resonators. For demonstration, two circuits including 4 resonators were fabricated and tested.Öğe A Novel Compact Microstrip Diplexer with Closely Spaced Channels(IEEE, 2020) Gorur, Ali Kursad; Turkeli, Alper; Dogan, Engin; Karpuz, Ceyhun; Gorur, AdnanA novel microstrip diplexer with closely spaced channels is introduced by using stub loaded dual-mode square loop resonators (DMSLRs). The proposed resonator is constructed by locating open-circuited stubs with narrow slits to the midpoints of a conventional DMSLR to achieve size reduction. By changing the number of narrow slits, resonant frequencies of the proposed resonator can be controlled. In order to design a diplexer with low channel frequency ratio, two stub loaded DMSLRs having different number of narrow slits are coupled to input and output ports by thin film capacitors. The designed diplexer was also fabricated and measured with a channel frequency ratio of 1.10. The channels were measured at 1.78 GHz and 1.96 GHz with the fractional bandwidths (FBW) of 5.4% and 5.3%, respectively. The measured insertion losses of the channels are 1.99 dB and 1.78 dB. Isolation between the output ports was obtained as better than 28 dB.Öğe Design of Tunable Microstrip Bandstop Filter(IEEE, 2016) Gorur, Ali Kursad; Karpuz, Ceyhun; Gorur, Adnan; Dogan, Engin; Uysal, BarisIn this paper, a novel microstrip bandstop filter with tunable center frequency and bandwidth is introduced. A dual-mode square loop resonator and three varactor diodes are used to achieve the tunability operation. The dual-mode square loop resonator is coupled to a straight transmission line that connects input and output ports. One of the varactors is used as a perturbation element on the symmetrical axis of the resonator and even mode resonance frequency can be tuned by changing the capacitance of its. Remaining two varactors are located at the lateral arms of the resonator as reference elements and they have task on the tunability of the odd mode resonance frequency. Depending on the capacitance changes of the varactors, both of center frequency and bandwidth of the stopband can be tuned. The designed filter was also fabricated and measured for the experimental verification of the predicted results.Öğe Design of tunable microstrip diplexer with reconfigurable filtering characteristics based on dual-mode square loop resonators(Wiley, 2020) Gorur, Ali Kursad; Dogan, Engin; Karpuz, Ceyhun; Gorur, AdnanA novel compact microstrip diplexer with tunable centre frequencies and reconfigurable filtering characteristics at both channels is presented. The designed diplexer is constructed by coupling two dual-mode square loop resonators (DMSLRs) having different electrical lengths. The DMSLRs are investigated by virtue of the coupled line analysis to evaluate the resonance frequencies, transmission zeros and out-band insertion loss level more conveniently. Centre frequencies of both channels can be independently tuned by the varactor diodes utilised instead of perturbation and reference capacitances. Depending on the specialised values of perturbation and reference capacitances, filtering characteristics of both channels can be reconfigured in terms of transmission zeros. The designed diplexer was fabricated and tested for the experimental studies and the measurements were obtained in a good agreement with the predicted results. Tuning ranges of the measured centre frequency in the first channel are between 1.23 and 1.43 and 1.35 and 1.64 GHz for the filtering characteristics with right- and left-side transmission zeros, respectively. In the second channel, they are 2.07-2.31 and 2.14-2.51 GHz for the filtering characteristics with real- and imaginary-axis transmission zeros, respectively. Isolation between two channels has been obtained better than 22 dB.Öğe Dual-mode dual-band microstrip bandstop filter design with independently tunable center frequencies(Wiley, 2017) Gorur, Ali Kursad; Filiz, Ayse Nihan Basmaci; Dogan, Engin; Karpuz, Ceyhun; Gorur, AdnanIn this article, a novel dual-mode dual-band bandstop filter design with independently tunable center frequencies is presented by using dual-mode square loop resonators. Tuning operation can be achieved with a constant fractional bandwidth. Varactor diodes are used instead of perturbation and reference elements. Two dual-mode square loop resonators in different electrical lengths are coupled to a transmission line connecting input and output ports. Center frequencies of both stopbands can be independently tuned by changing the capacitances of varactor diodes of both perturbation and reference elements. While the perturbation and reference varactors tune even mode resonance frequency together, odd mode resonance frequency can only be tuned by reference varactors. The designed filter was also fabricated for the experimental studies and it exhibits acceptable tunability operations in measurements. Center frequencies of the first and second stopbands can be tuned between 2.2 and 2.54 GHz and between 3 and 3.38 GHz, respectively. Rejection levels for both stopbands were obtained as better than -13 dB in the whole tuning range.Öğe Multibit Chipless RFID Tags Based on the Transition Among Closed- and Open-Loop Resonators(IEEE-Inst Electrical Electronics Engineers Inc, 2022) Gorur, Ali Kursad; Dogan, Engin; Ayas, Gizem; Karpuz, Ceyhun; Gorur, AdnanIn this article, a novel and simple design procedure for multibit chipless radio frequency identification (RFID) tags is introduced, which is based on the characteristics of dual-mode loop resonator (DMLR) and open-loop resonator (OLR). By removing a small patch element from the symmetry axis of the DMLR, a simple geometrical transition to an OLR to obtain different frequency codes can be achieved. Since the DMLR and OLR provide dual- and single-resonant frequencies, three different frequency codes can be observed using one resonator. Thus, 3 $<^>{N}$ codes can be performed by coupling N resonators to input/output (I/O) ports. Even-odd mode analysis over the coupling mechanism of a single resonator is provided to characterize the frequency responses of the proposed resonators. To prove the proposed approach, two multiresonator circuits having four resonators were fabricated and tested in a good agreement. In the test environment, two horn antennas and a vector network analyzer have been utilized as transmitter and reader. Next, in order to achieve size reduction, meandered resonators are utilized instead of conventional DMLR and OLR. Based on these resonators, two RFID tags, including wideband monopole antennas integrated into the seven-resonator circuits on the same board, were also fabricated and tested.Öğe Novel Chipless RFID Tags Using Eight State Triple-Mode Resonators(IEEE-Inst Electrical Electronics Engineers Inc, 2023) Dogan, Engin; Gorur, Ali Kursad; Gorur, AdnanFor multi-resonator based chipless radio frequency identification (RFID) tags, a novel triple-mode resonator is designed by loading open-circuited stubs to a transmission line which is coupled to input and output ports. Since the proposed resonator provides independently controllable three resonant frequencies, three bits can be obtained by means of a single triple-mode resonator. The presence and absence of the open stubs results in eight states from a single triple-mode resonator. Therefore, N triple-mode resonators in different lengths can generate 8(N) different frequency codes. For this purpose, a multi-resonator circuit operating between 1.9 and 3.75 GHz is also developed by using 5 triple-mode resonators, so that 15 resonant frequencies can be obtained. Two conventional vertically/horizontally polarized monopole antennas are used to demonstrate the tag performance. Bit density and spectral efficiency of the designed tag are 29.04 bits/ lambda(2)(g) and 8.33 bits/GHz. Two chipless RFID tags having different frequency codes have been fabricated and tested in a good agreement with the predicted results. The designed tags have also been tested under various circumstances successfully.Öğe Novel flexible chipless RFID tags based on five state resonators(Taylor & Francis Ltd, 2023) Dogan, Engin; Gorur, Ali Kursad; Gorur, AdnanIn this paper, novel chipless radio frequency identification (RFID) tags are designed by using asymmetrical triple mode resonators constructed by an open loop resonator with two open stubs in different lengths. Three transmission zeros (bits) can be obtained by coupling a proposed resonator to a straight feeding line that connects input/output ports. Five frequency codes can be achieved with respect to the existence of the open stubs and the open loop resonator. By coupling eight asymmetrical triple mode resonators to the feeding line, a multi-resonant circuit is developed on a flexible substrate of Rogers 5870. Totally 24 bit frequencies can be achieved and it is possible to identify 5(8) different items. For the chipless RFID tags, two monopole wideband antennas in vertical/horizontal polarizations are integrated instead of the input/output ports. Two tags have been fabricated and tested to demonstrate the identification of different codes under smoothed and curved positions successfully.Öğe Novel Multi-Resonator Circuits for Chipless RFID Tags Using Asymmetrical Triple-Mode Resonators(IEEE, 2022) Gorur, Ali Kursad; Dogan, Engin; Karpuz, Ceyhun; Gorur, AdnanIn this paper, a new asymmetrical triple-mode resonator (TMR) that can be used in chipless radio frequency identification (RFID) tags is introduced. The proposed resonator is constructed by locating two open-circuited stubs in different electrical length to an open loop resonator (OLR). Two resonant frequencies can be controlled by these asymmetrical stubs, while the main resonant frequency is resulted from the nature of the OLR. It is proven that the proposed resonator can allow obtaining 5 frequency codes from a single TMR. A multiresonator circuit is also designed by coupling 6 TMRs to a bended transmission line which connects input to output port. For the experimental verifications, three circuits having different frequency code combinations have been fabricated and measured in an excellent agreement with the simulated results. Totally 18 resonant frequencies resulted from the 6 TMRs have been clearly observed in the measurements. The proposed multi-resonator circuit can be utilized for chipless RFID tags and 5(6) frequency codes can be generated.Öğe Quintuple-mode wideband bandpass filter based on stub-loaded circular resonator(Wiley, 2022) Gorur, Ali Kursad; Dogan, Engin; Gorur, AdnanIn this paper, novel compact wideband filters have been implemented using a stub-loaded microstrip resonator based on a circular open-loop configuration for the first time. To offer an alternative wideband filter configuration, the quadruple-/quintuple-mode wideband bandpass filters (BPFs) using stub-loaded circular microstrip resonator (SLCMR) and parallel-coupled microstrip line (PCML) feed configuration are proposed. They are realized by employing a single open stub and two open stubs, respectively. A half-wavelength (>lambda/2) circular microstrip resonator (CMR) loaded with two open stubs excites three resonant modes, while the one with a single stub produces two resonant modes. One of the modes is odd-mode generated by a lambda/2 CMR, the others are even-modes excited by the two loading stubs. The PCML with enhanced input/output (I/O) coupling degree excites also two modes in the passband. Two loading stubs not only creates transmission poles in the passband, they also create two transmission zeros in the lower and upper stopbands. The quadruple-/quintuple-mode wideband BPFs with fractional bandwidths FBW of 60% and 62% are successfully realized by using the SLCMR and PCML feed configuration together. Both filters are designed, fabricated, and tested where excellent agreement between simulated and measured results is observed.Öğe Single-wideband and dual-band bandpass filters based on compact quadruple-mode resonator(Taylor & Francis Ltd, 2024) Gorur, Ali Kursad; Dogan, Engin; Gorur, AdnanA stub-loaded U-shaped microstrip resonator (U-SLR) exciting two odd-modes and two even-modes and its applications to single-wideband and dual-band bandpass filter (DB-BPF) are introduced. The parallel-coupled lines (PCLs) at input/output (I/O) ports can provide a wideband response by exciting two additional modes in the passband, so-called PCLs modes. In addition to the transmission poles (TPs) in the passband, two transmission zeros (TZs) in the lower and upper stopbands can be created by the loaded stubs. A compact size, high-selectivity, and low insertion loss WB-BPF is designed, fabricated, and tested. Moreover, a compact and low loss DB-BPF with closely spaced passbands is designed and tested. TZ-shifting method is used to design a DB-BPF by splitting the wideband. To achieve this, it is sufficient to change the length of only one of the loaded stubs. The calculated, simulated and measured frequency responses for both single-wideband and DB-BPFs are in very good agreement.Öğe Wideband filtering power dividers with/without notch band(Wiley, 2024) Gorur, Ali Kursad; Dogan, Engin; Karpuz, Ceyhun; Gorur, AdnanLow loss and compact wideband filtering power dividers (WB-FPDs) with/without notch band are proposed. The WB-FPDs are designed using wideband bandpass filter based on asymmetric stepped-impedance resonator (SIR). Parallel coupled microstrip lines are used to create both wideband filtering characteristic and two additional transmission poles. A notch band can be generated at upper passband edge by using open-circuited stubs on the SIRs. The WB-FPDs with/without notch band are successfully designed, fabricated, and tested. The wide passband is centered at 4 GHz with the fractional bandwidth (FBW) of 51.1%, while the notch band is at 5.56 GHz with the FBW of 3.1%. Good agreement between the simulated and measured results is observed.
