Conventional Stepped-impedance Resonator Research Articles

Dual‐band BPF design using ASIR structures with a dumbbell‐shaped notch

ABSTRACTPresented is a miniaturized microstrip dual‐band bandpass filter (BPF). An asymmetric stepped impedance resonator (ASIR) is employed with a dumbbell‐shaped notch. Compared with the conventional stepped impedance resonator (CSIR) and the multiple‐mode resonator (MMR), the ASIR utilizes the first two modes to produce a wider lower passband, while the third mode produces an upper passband. The input and output ports of the ASIR are connected with interdigital capacitive‐coupled lines. The measured data of the fabricated filter demonstrates a very good agreement to those simulated with a steep upper‐stopband suppression. The filter simultaneously operates at 13.88 and 24.75 GHz, respectively, with the corresponding fractional bandwidths of 29.4% and 7.1%. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:532–535, 2016

Compact bandpass filter with multiple transmission zeros using modified stepped-impedance resonators

A modified quarter-wavelength stepped-impedance resonator (SIR) is proposed and analyzed in this article. In the modified SIR, the low characteristic impedance stub of a conventional SIR is replaced by a closed rectangular loop. Based on the modified SIRs, a compact third-order bandpass filter (BPF) with multiple transmission zeros is presented. The filter consists of two novel SIRs and one half-wavelength embedded spiral-line resonator locating in the closed rectangular loops. Mixed-cross (M–C) coupling and source–load (S–L) coupling are introduced to the filter. Owing to the M–C coupling and S–L coupling, multiple transmission zeros and the suppression of harmonics can be obtained in the stopband for the enhanced frequency selectivity. A new BPF centered at 2.4 GHz with 25% fractional band width for wireless local area networks application has been designed, fabricated and measured to verify the validity of the above method.

A novel compact triband bandpass filter using SIR embedded quarter-wavelength resonators

A novel second-order triband bandpass filter using stepped-impedance resonator embedded quarter-wavelength resonators (SIREQRs) is presented in this letter. By embedding a meandered stepped-impedance resonator (SIR) into the low-impedance section of the conventional quarter-wavelength SIR, the proposed resonator is obtained. By coupling two SIREQRs with a common short-ended via-hole and feeding them through a pair of open-loop resonators, the proposed second-order triband filter is achieved. The first passband is generated by the quarter-wavelength SIRs, the second one is created by the embedded resonators, and the side-coupled open-loop resonators are utilized to construct the third one. Seven transmission zeros are generated due to the 0° feed structure and the canceling effects between electric coupling and magnetic coupling, which improve the skirt selectivity and band-to-band isolation level greatly. Furthermore, the overall circuit size is very compact with only 7.2 × 12.6 mm2 or 0.08 × 0.144 λg2 due to the embedded configuration. A triband filter prototype has been designed and fabricated, and the measured results agree well with the simulated ones. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1345–1349, 2015

A coupled line bandpass filter using a novel SIR with intentional coupled length

ABSTRACTA novel stepped impedance resonator (SIR) and its design formulas for the coupled line bandpass filter (BPF) are proposed. The proposed SIR can provide tight coupling by intentionally extending the length of a coupled line. In addition, it forms the second passband much farther away compared to the conventional SIR. To show the validity of the proposed SIR and its application to the coupled line BPF, the three‐pole SIR BPF is designed and fabricated. The measured and simulated results are in very good agreement. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1259–1262, 2015

A Novel Cross-Coupled Filter Through Mixed Coupling Path with Multiple Tunable Transmission Zeros

A novel bandpass filter with multiple transmission zeros using a mixed-coupling microstrip stepped-impedance resonator is proposed and investigated in this article. A microstrip with a grounded via hole is added in the middle of the improved microstrip stepped-impedance resonator; the coupling gap and the grounded via hole act as the electric and magnetic coupling, respectively, by which additional transmission zeros can be generated near the passband. Based on the proposed filter topology, a fourth-order bandpass filter with five transmission zeros is fabricated and measured. Compared with a conventional cascaded-quadruplet filter, the novel designed filter has sharper rejection with a symmetrical response and more compact size. Moreover, the proposed idea leads to a new solution to decrease size as well as increase the capability of the conventional stepped-impedance resonator filters.

Compact and high-performance bandpass filter and diplexer based on SCMRC-loaded SIR

Bandpass filter (BPF) and diplexer, which are required to be compact size and high performance, are widely used in modern wireless communication systems. In this article, novel BPF and diplexer are designed using the proposed resonator called spiral compact microstrip resonator cell (SCMRC)-loaded stepped-impedance resonator (SIR). The SCMRC-loaded SIR is proposed using the slow-wave structure SCMRC to replace the low-impedance section of the conventional SIR. Compared with the conventional SIR, the new SCMRC-loaded SIR has a compacter size and can generate a transmission zero above its fundamental resonant frequency. As examples, a BPF with the central frequency at f 0 = 1 GHz and a diplexer operating at 0.9/1.57 GHz are designed and fabricated. The fabricated BPF occupies a compact size of 0.07 λ 0 × 0.035 λ 0 and has a −60 dB rejection level wide stopband from 1.2 f 0 to 3.8 f 0. The fabricated diplexer occupies a compact size of 0.076 λ 0 × 0.128 λ 0 and has an up to −50 dB output isolation. Good agreement can be observed between the simulations and the measurements.

Dual-wideband branch-line coupler based on a loaded N-segment SIR

In this study, a novel topology of loaded N-segment stepped-impedance resonator (SIR) is introduced to control the frequency ratio between the second and first resonance frequencies of such resonator. The fundamental characteristic of such resonators, the frequency ratio between the second and first resonance frequencies, is targeted as a key factor in arbitrary tuning the resonance frequencies. It is shown that this factor can be determined in a ratio of 6.7: 2.7: 2.25 for the proposed, the conventional dual-section and T-shaped SIRs using a five-segment SIR. This concept can be applied in the design of any dual-band microwave components where a wide branch-line couplers is chosen as a sample. It is demonstrated that the proposed topology not only provides more design flexibilities but also improves the performance of such components in terms of bandwidth enhancement, better return loss, and size reduction around 56%. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2300–2303, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27076

Ultra wideband filter using dumbbell-etched stepped impedance resonator

In this article, an ultra wideband bandpass filter using the dumbbell-etched stepped impedance resonator (SIR) is presented. The filter consists of a dumbbell-etched SIR with an impedance ratio K > 1 and the enhanced coupled input/output lines. The SIR is folded into a dumbbell shape to achieve a smaller circuit size than the filter with conventional SIR. The bandwidth can be analysed using the image-parameter method to obtain the proper dimension of the coupled lines and verified using electromagnetic simulation. The measured 3 dB fractional bandwidth of 110% and insertion loss |S 21| less than 3 dB over the entire passband are achieved.

A High Selectivity Dual-Band Filter Using Ring-Like Sir with Embedded Coupled Open Stubs Resonators

We present a design of dual-band bandpass filter (BPF) using a ring-like stepped-impedance-resonator (SIR) and embedded coupled open stubs for application to a wireless local area network (WLAN). The dual-passbands are created by optimally selecting the impedance ratio (K) and length ratio (u) in the resonant behavior of a conventional SIR. Without increasing the circuit size, the performance of the second passband can be enhanced by adding the coupled open stubs in the ring-like SIR. The proposed filter was designed and fabricated. The measured results have a return loss larger than 24 dB, a low insertion loss less than 1.3 dB, and a fractional bandwidth (FBW) of 15% at 2.4 GHz, as well as a return loss larger than 12 dB, a low insertion loss less than 2 dB, a FBW of 2% at 5.7 GHz, and transmission zeros at 2.09, 2.96, 5.44, and 6.11 GHz near the passband edges. It is verified that experimental results show a good agreement with the simulated results.

A High Performance Bandpass Filter with a Wide and Deep Stopband by Using Square Stepped Impedance Resonators

In this paper, a microstrip bandpass filter with a wide and deep stopband by using the modified stepped-impedance resonator (SIR) was designed and implemented. The modified SIR is formed by properly folding the conventional SIR to be a square open-loop SIR. By analyzing the admittance of the even and odd mode, the transmission zero of the modified SIR can be easily found, thus having a wide and deep stopband simultaneously. Bandpass filter (BPF) can have high performances with a wide and deep stopband as well as good selectivity by using the proposed SIR, compared to the conventional SIR. A filter example centered at f 0 of 1.26 GHz has been implemented to verify the design concept. The results showed that the |S 21| was greater than 65 dB at the spurious response of 2f 0 and a wide stopband with a rejection level over 50 dB is extended from 1.5f 0 to 3.5f 0. Moreover, experimental results have a good agreement with the simulated results.

A Compact Dual-Band Bandpass Filter with High Band Selectivity using Cross-Coupled Asymmetric Sirs for Wlans

In this paper, we have proposed the design of novel compact dual-band bandpass filter (BPF) with high band selectivity by using only two asymmetric stepped impedance resonators (SIRs) with one step discontinuity. By arranging the cross-coupled SIRs, three transmission zeros near the passband edges and a high isolation between two passbands are introduced to improve the band selectivity of the proposed filter. The dual-band frequencies of this BPF is implemented by properly selecting the impedance ratio (R) and physical length ratio of the asymmetric SIRs. The bandwidths and the coupling coefficients of the two passbands (2.4/5.2 GHz) can be designed by adjusting the coupling gap between the resonators. The proposed BPF has a smaller circuit size in comparison with previous works using conventional direct-coupling SIRs. The measured results are in good agreement with the full-wave simulation ones.

Fabrication-Tolerant Microstrip Quarter-Wave Stepped-Impedance Resonator Filter

The etching error causes serious frequency drift of a microstrip stepped-impedance resonator (SIR). This paper proposes a novel microstrip quarter-wave SIR structure, which is insensitive to fabrication tolerances. Inserting several ground strips in the low-impedance section of the resonator keeps the impedance ratio almost constant in spite of inaccurate fabrication. As an additional benefit, the resonator size would be miniaturized because the characteristic impedance of the microstrip line in the low-impedance section is mainly controlled by the signal strips and the inserted ground strips in a coplanar manner. The concepts and characteristics of this modified resonator structure are discussed in detail. The filters constructed by the conventional microstrip SIR were also designed and fabricated at the same frequency band to compare with the proposed ones. Measured results show that each proposed filter has compact size, wide stopband, and high tolerance to fabrication errors. Two four-pole cross-coupled filters were designed and fabricated to demonstrate the feasibility.

Design of dual‐band SIR bandpass filter with a broad upper rejection band for WLANs

AbstractIn this letter, we proposed the design of novel dual‐band bandpass filter (BPF) with a broad upper rejection band using only two asymmetric stepped impedance resonators (SIRs), which has a smaller circuit size in comparison of previous works. The feature of the asymmetric SIR is only one‐step discontinuity, which is different from the conventional SIR with two‐step discontinuities. By selecting properly the impedance ratio (R) and physical length ratio (α) of the proposed asymmetric SIRs, the low loss dual‐band BPF centered at 2.4/5.2 GHz with a wide upper rejection band from 6 to 14 GHz can be implemented perfectly. The bandwidths and the coupling coefficients of the two passbands can be tunable by adjusting the coupling gap distance between the resonators, which are calculated by using full‐wave simulator IE3D. Good agreement between the electromagnetic (EM) simulation and measurement is reported. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1143–1146, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24227

Microstrip Cross-Coupled Tri-Section Stepped-Impedance Bandpass Filter with Wide Stop-Band Performance

A compact microstrip bandpass filter with wide stop-band is presented in this paper. The wide stop-band is achieved by introducing tri-section stepped-impedance resonator (SIR). It offers further reduced overall size than conventional two-section SIR. The measured results exhibit the good filtering performance. Two transmission zeros ensure a high out-of-band rejection. With the new structure, the filter has not only wide stop-band performance with harmonic frequency outside 4.12ƒ 0 but also compact size.

A novel compact dual‐band bandpass filter using asymmetric SIRs for WLANS

AbstractIn this article, a novel compact dual‐band bandpass filter (BPF) using asymmetric stepped impedance resonators (SIRs) has been presented for the first time. The feature of the proposed asymmetric SIR is only one step discontinuity, which is different from the conventional SIR with two step discontinuities. The frequency response of the dual‐band at 2.4/5.2 GHz can be achieved by determining the impedance ratio (K) and physical length ratio (α) of the asymmetric SIR. The coupling coefficient between the coupled asymmetric SIRs is calculated by using full‐wave simulator IE3D. A dual band BPF is designed, fabricated, and measured. The measured results are in good agreement with the full‐wave simulation results. Additionally, the BPF has a smaller circuit size in comparison of previous works. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1237–1240, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23339

Miniaturized coplanar waveguide bandpass filters using multisection stepped-impedance resonators

We report several types of coplanar waveguide tri-section stepped-impedance resonator (SIR) structures that offer further size reduction compared to the conventional two-section SIRs. In addition, the tri-section SIRs provide flexibility of introducing effective capacitive coupling to the ground lines for realizing slow-wave structures. The slow-wave effect can be used to implement more compact bandpass filters. The principles of achieving size reductions using tri-section SIRs are described and confirmed by simulation results. To demonstrate the effectiveness of the proposed tri-section SIRs in size reduction, the tri-section SIRs with slow-wave effects were implemented in a two-pole directly coupled bandpass filter and a fourth-order quasi-elliptic bandpass filter with reduced size. The measured results matched well with the theoretical prediction.