Stepped Impedance Resonators Research Articles

A single‐layer differential‐fed dual‐band filtering antenna for WLAN application

AbstractIn this letter, a single‐layer differential‐fed dual‐band filtering antenna for wireless local area network application is proposed. The proposed antenna consists of a square patch, and two pairs of stepped impedance resonators (SIRs). The lower operating passband is realized by exciting the square patch with a pair of differential ports. Then, a pair of SIRs is connected with the radiating edge of the square patch to introduce another resonance, thus forming the upper passband. And a radiation null is simultaneously produced to enhance the frequency selectivity between the two passbands. Moreover, another pair of SIRs is utilized to connect with the nonradiating edge of the square patch, which generates an additional high‐frequency in‐band resonance and a radiation null to further improve the bandwidth and frequency selectivity of upper passband. The developed prototype was fabricated and measured to verify the design concept. The measured results are in good agreement with the simulated ones, demonstrating that it exhibits −10 dB fractional impedance bandwidths of 3.68% and 7.35%, maximum realized gains at boresight direction of 5.5 and 8.7 dBi, and cross‐polarization levels smaller than −30 dB, in lower and upper passbands, respectively.

Wideband bandpass filters with suppressed harmonics using vertically installed planar structures

AbstractThis article presents a closed‐form synthesis method for wideband bandpass filters with suppressed harmonics, where stepped‐impedance resonators (SIRs), scaled lines, and vertically installed planar (VIP) structures are introduced to improve the in‐band and out‐of‐band performances. By combining SIRs and scaled lines, the rejection level of the filter is greatly improved and a more compact size is achieved. And the VIP structures help to bring wide passband as well as suppressed harmonics. Then, a 3rd‐order filter is designed to verify the validity of the proposed method and topology. The simulated and measured results demonstrate that the proposed design has a wide passband (FBW = 52.9%), low insertion loss (<0.4 dB), and suppressed harmonics with the level of 20 dB up to 7.1f0.

Design of a Novel Balanced-to-Balanced Dual-Band Diplexing Power Divider

In this brief, a balanced-to-balanced (BTB) dual-band diplexing power divider (DBDPD) implemented on a new asymmetric series T-junction MS transition is proposed. Firstly, a four-way BTB power divider (PD) as feed network was designed. The T-junction microstrip-slotline (MS) transitions are employed to realize phase shift and power division within a wide bandwidth. The balanced U-type MS transitions are adopted at each balanced port, which can realize superior common-mode (CM) suppression intrinsically while the differential-mode (DM) responses are independent. Then, the BTB DBDPD is realized by adding four pairs of step impedance resonators (SIRs) asymmetrically to the series T-junction. As a result, an asymmetric series T-junction MS transition with diplexing function is formed, which can flexibly adjust the operating passbands and adapt to the balanced port. Meanwhile, SIRs are employed to realize four sharp passbands. So as to verify the feasibility of the theoretical design, the proposed designs are manufactured. A good agreement can be observed between the simulation and measurement.

Magnetodielectric Material Characterization Using Stepped Impedance Resonators

Two resonance-based methods for magnetodielectric (MD) material characterization are presented in this article using stepped impedance resonators (SIRs). A single SIR (SSIR) is initially used to create two spatially separated sensing areas for permittivity and permeability measurements predicated on the resonance frequency variation. Next, a differential-based sensing method, based on resonance frequency splitting, is introduced for permittivity and permeability differential measurements. For this purpose, four spatially separated sensing areas are established on a single resonance structure using a double SIR (DSIR). The presented sensors provide a reliable sensing method for MD characterization and comparison. The proposed sensing methods are validated through numerical analysis based on electromagnetic (EM) simulation and experimental measurement of materials with different intrinsic EM properties.

Dual-wideband sandwich coupled three-lines bandpass filter based on modified open-stub loaded stepped impedance resonator with improved second harmonic for 5G wi-fi/ ku-band applications

A modified open-stub-loaded three sections stepped impedance resonator (OSL-TSIR) is analysed in this paper. Based on the even- and odd-mode analysis technique, it can be easily achieved that the proposed OSL-TSIR have the advantage of improving spurious resonant mode frequencies. Besides, more degrees of freedom are provided to control the location of harmonics. A third order Chebyshev dual-wideband bandpass filter composed of cascade parallel sandwich coupled three-lines sections of types SC/CS and OSL-TSIR which act as multi-mode resonator was developed and the design procedure is described. To demonstrate the efficiency of the design process, DB-BPF operating at 5.15/12.58 GHz (2.45 f0) and FBW of 19/5.7% for 5G Wi-Fi/Ku-band Applications is designed and simulated. Three transmission zeros are created, resulting in the excellent band-in-band isolation and high selectivity. The filter has a miniaturized size of 27 mm × 18 mm.

A Compact Passive Quad‐Band Negative Group Delay Circuit With Stepped Impedance Resonator and Defected Microstrip Structure

AbstractBased on two‐stage stepped impedance resonator (SIR) and defected microstrip structure (DMS) with an E‐shaped slot, a novel compact passive quad‐band negative group delay circuit (NGDC) is proposed whose resonation frequencies and group delay performance are mainly determined by the SIR and the DMS. In order to help reveal the working mechanism of the quad‐band NGDC, an equivalent circuit of the NGDC is developed. It is composed of the transmission lines and serial‐parallel LC networks, and its S‐parameters are derived by using the theory of transmission matrix. The theoretical and simulated results for the transmission characteristics of the NGDC agree well with each other. To validate the design concept, a prototype of the proposed quad‐band NGDC was fabricated and measured. The measured results show that at the frequencies of 2.64, 7.88, 13.08, and 18.18 GHz, the negative group delay values achieve −5.4, −3.1, −1.18, and −1.14 ns, with |S21| values of −17.2, −20.5, −12.8, and −18.1 dB, respectively. Compared with the recently reported works, the proposed NGDC exhibits the largest number of operation frequency bands. Furthermore, it does not use lumped resistors and has miniaturized dimension.

Design of Microstrip Dual-Band Bandpass Filter for Sub-6 GHz 5G Mobile Communications.

In this paper, a microstrip bandpass filter for dual-band sub-6 GHz 5G mobile communications is designed. The two first resonance frequencies of the stepped-impedance resonator are used as the operating frequencies of the two passbands. Furthermore, the stepped-impedance resonator is folded to form open-loop stepped-impedance resonator for compactness. This form of the resonator generates a second transmission zero in the upper stopband which improve the out of-band rejection. A 50 Ω tapped-line input/output is used to feed the filter. The proposed structure is designed, analyzed and manufactured and their measured results are found to be in good agreement with the simulation results. From the measured results, it is found that the proposed filter achieved return loss of 21 dB and 28.3 dB, insertion loss of 0.4 dB and 1.7 dB and bandwidth of 12.5 % and 10.81% at 3.61 GHz and 5.55 GHz, respectively. In addition, the proposed filter has a compact size which make it suitable for sub-6 GHz 5G mobile communications.

A Novel Miniaturized Image Rejection Bandpass Filter Basing on Stepped-impedance Resonators

A Novel Miniaturized Image Rejection Bandpass Filter Basing on Stepped-impedance Resonators

Design of Compact Quasi-Elliptic Bandpass Filters Based on Coaxial Inset Resonators

This article reports a novel inset resonator configuration for coaxial filter applications with quasi-elliptic responses. The design and analysis of the inset resonator are discussed in detail and accurately modeled as a capacitively-loaded stepped-impedance half-wavelength resonator featuring more compactness, high quality factor, and enhanced spurious responses in comparison with conventional half-wavelength and combline resonators. Additionally, the operating frequency can be tuned intrinsically through the displacement of the coaxial resonator, eliminating the need for any additional tuning elements and maintaining a stable quality factor. Two quasi-elliptic inset resonator type filters are implemented in planar and longitudinal coupling configurations, respectively. The first takes the form of a folded four-pole 2.93 GHz filter with two symmetrical transmission zeros. The fabricated filter has a compact structure of 29.76 cm 3, an insertion loss better than 0.73 dB, a return loss better than 18 dB, and a wide spurious-free band up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.5\cdot f _{0}$ </tex-math></inline-formula> . The second inset-type quasi-elliptic filter is realized in a longitudinal inline arrangement. An example of a 2.53 GHz three-pole filter is presented with a closely-positioned transmission zero, wide spurious-free band ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\approx 3\cdot f _{0}$ </tex-math></inline-formula> ), and a very compact structure of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$55.7\times 33\times 33$ </tex-math></inline-formula> mm 3.

Design of Tunable Coaxial Bandpass Filter Based on Embedded Stepped Impedance Resonators

Design of Tunable Coaxial Bandpass Filter Based on Embedded Stepped Impedance Resonators

Quasi-elliptic Triple Passband Filter Using Stub Loaded Step Impedance Resonator and Non-resonating T structure

Quasi-elliptic Triple Passband Filter Using Stub Loaded Step Impedance Resonator and Non-resonating T structure

A low-loss dual-band bandpass filter using open-loop stepped-impedance resonators and spur-lines for sub-6 GHz 5G mobile communications

&lt;abstract&gt;&lt;p&gt;This article presents the design of a low-loss microstrip dual-band bandpass filter with improved inter-band isolation and selectivity for 5G sub-6 GHz mobile communications. The proposed filter utilizes the two first resonance mode frequencies provided by the stepped-impedance resonator to generate its two passbands at 3.6 GHz and 3.5 GHz, and spur-lines located before the input/output ports to improve the isolation and selectivity between passbands. The filter is designed using an RT/Duroid 5870 substrate with a relative permittivity of 2.33 and a thickness of 0.79 mm, manufactured and tested to validate the proposed design. The experimental results show that the filter operates at 3.61 GHz and 5.51 GHz with a 3-dB fractional bandwidth of 12.74% and 16.7%, respectively. Insertion losses at the two passbands center frequencies are 0.6 dB and 0.9 dB. In addition, the proposed filter has the advantage of covering the licensed and unlicensed 5G bands and provides a simple structure without using vias or DGS structures.&lt;/p&gt;&lt;/abstract&gt;

Design and Optimization of an S-Band MEMS Bandpass Filter Based on Aggressive Space Mapping.

Aggressive space mapping (ASM) is a common filter simulation and debugging method. It plays an important role in the field of microwave device design. This paper introduces ASM and presents the design and fabrication of a compact fifth-order microstrip interdigital filter with a center frequency of 2.5 GHz and a relative bandwidth of 10% using ASM. The filter used a double-layer silicon substrate structure and stepped impedance resonators (SIRs) and was optimized by ASM. After five iterations, the filter achieved the design specification, which greatly improves the efficiency of the filter design compared with the traditional method. It was fabricated on high-resistance silicon wafers by micro-electro-mechanical systems (MEMSs) technology, and the final size of the chip is 9.5 mm × 7.6 mm × 0.8 mm. The measurement results show that the characteristics of the filter are similar to the simulation results, which also shows the efficiency and precision of the ASM algorithm.

IPD Millimeter-Wave Bandpass Filter Chip Based on Stepped-Impedance Coupled-Line Dual-Mode Resonator for 5G Application

A novel stepped-impedance coupled-line dual-mode resonator (SICLDMR) is presented and analyzed in this brief. The resonator is a closed ring structure, constructed by two coupled lines with different impedances. The even- and odd-mode resonance frequencies of this SICLDMR are created due to the different effective dielectric constants of the two modes. Based on the proposed resonator, a simple bandpass filter (BPF) is designed by adding two symmetric open-stub feeding structures. For demonstration, a narrowband BPF operating at 35 GHz is simulated, fabricated by using the 100- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mu }\text{m}$ </tex-math></inline-formula> -thick-GaAs integrated passive device (IPD) technology. And the measured results show that the BPF with a good fractional bandwidth of 13% realizes a low insertion loss of 0.74 dB, sharp roll-off skirt of passband, and wide stopband rejection. The advantages of the proposed IPD BPF indicate that it has a promising application prospect in 5G millimeter-wave systems.

Design of a Dual-Wideband BPF with Parallel-Coupled Stepped Impedance Resonator and Open-Circuited Stubs

Design of a Dual-Wideband BPF with Parallel-Coupled Stepped Impedance Resonator and Open-Circuited Stubs

A micromachined ultra‐wide stopband lowpass filter based on stepped impedance resonator loaded T‐shaped structure

This article presents an additively manufactured micro-coaxial lowpass filter with ultra-wide stopband suppression. To achieve a wide stopband response, two-stage stepped impedance resonator loaded T-shaped structures are used to substitute the low impedance transmission lines in the lowpass filter prototype to generate extra transmission zeros in the stopband. Shunt open-ended stubs are introduced to the structure in flexible positions to further strengthen the suppression at specific frequency points. The filter is designed with 22 GHz passband and the 20 dB stopband suppression bandwidth over 300 GHz. The micro-coaxial lowpass filter structure was fabricated based on additive metal micro-manufacturing process with the rectangular cross-section dimensions of 0.5 mm × 0.5 mm (300 GHz cutoff frequency). To facilitate the measurement, pair of coax-to-CPW transitions are added at the input/output ports. The measurement results show excellent agreement from DC-110 GHz (limitation of the measurement device), with insertion loss of 1.05 dB at the cutoff frequency fc, which validates the design.

Attenuation‐tunable balanced bandpass filter based on graphene nanoplates

In this letter, a unique type of balanced bandpass filter (BPF) with high selectivity and tunable attenuation is proposed through the comprehensive design of a microstrip balanced BPF and graphene nanoplates. In order to achieve the passband response in differential-mode (DM) excitation and produce a wide and deep stopband in common-mode (CM) excitation, the balanced couple of lines are used in balanced BPF. The graphene nanoplates are loaded on the open ends of λ/4 stepped-impedance resonators to dissipate the electromagnetic field. By raising the bias voltage applied to the graphene nanoplates, the values of the graphene's surface impedance can be adjusted from high to low. The insertion loss of the balanced BPF can be indirectly tuned while maintaining the return loss at a comparatively low level. A prototype of the proposed gain tunable balanced BPF is fabricated and measured. The measured results show that a tuning range of insertion loss from 1.75 to 10.7 dB can be obtained for the DM circuit over the operating bandwidth centered at 1.84 GHz, without interrupting the signal rejection of the CM circuit.

Design of Wideband Filtering Quadrature Coupler Consisting of Inductor-Loaded Coupled Line With Three-Coupled-Lines

In this brief, the design of a wideband filtering quadrature coupler is presented. It is composed of an inductor-loaded coupled line (I-CL), two open-ended stubs, four short-ended stepped impedance resonators, and four three- coupled-lines (TCLs). Wideband operation with three resonant points is generated by using the I-CL with the TCLs. Due to the utilization of short-ended resonators combined with the open stubs, wide stopband is also obtained. Design formulas are derived using the even-odd decomposition technique and optimization process is given for guidance. For demonstration, a 3-dB prototype is designed, fabricated and measured. Measurement results show that a bandpass bandwidth (BPBW) of 43% is realized under the criterions of 15-dB return loss and isolation. While the BPBWs for 0.5-dB amplitude imbalance and 5° phase difference fluctuation are 40.3% and 48%, respectively. Besides, wide stopband extends to 2.64 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${f} _{0}$ </tex-math></inline-formula> is realized with more than 10 dB rejection level.

Design of a novel compact highly selective wideband bandstop RF filter using dual path lossy resonator for next generation applications.

This article presents the design of a wideband bandstop RF filter intending to improve selectivity and compactness. Conventional bandstop filter topology with finite unloaded quality factor produces degraded bandstop filter performance due to dissipation loss. In the proposed filter design, a novel dual path Capacitive Coupled Step Impedance Resonator (CCSIR) structure is used to obtain an infinite stopband attenuation. A uniform impedance resonator is used in Path 1, whereas Path 2 contains a resonator that is twice coupled to the transmission lines. The electrical length of both paths is chosen to be out of phase, resulting in a high rejection level at higher frequencies. It has been analyzed that the selectivity can be improved by increasing the order of the dual coupled step impedance resonator. The proposed design produces a wideband BSF centered at 5.25 GHz with a high rejection level of 104.3 dB and fractional bandwidth of 58.5%. The results have demonstrated that the resonant frequencies are regulated by varying the electrical length of CCSIR. Moreover, it has been realized that out of phase signal cancellation due to the dual path is involved in producing the finite frequency transmission poles, which further enhances the filter selectivity. However, the same electrical performance can only be achieved from coaxial cavities and waveguides due to the high-quality factor. The proposed topology is fabricated and measured on a high-frequency microstrip substrate having a low-quality factor with a compact output and better electrical performance compared to coaxial cavities or waveguides. Due to its high electrical performance and small size, the proposed BSF is appropriate for 4G and 5G (FR1) applications. The measurement shows good concurrence with the full-wave EM simulated results. The fabricated prototype of third order BSF has a compact size of (0.7 × 0.77)λg at 5.25 GHz.

A new compact, wide bandwidth dual‐passband microstrip filter based on dual‐mode stepped‐impedance‐resonators

In this article, a new compact, wide bandwidth dual-band bandpass filter (DB-BPF) with four transmission zeros (TZs) is proposed. A dual-path configuration is realized by cascading different dual-mode resonators. The novel dual-mode resonators are based on stepped impedance resonators (SIRs) that generate the TZs owing to their intrinsic characteristics. The proposed DB-BPF can fulfill simultaneous independent control of the external and internal-resonator coupling. The design procedure based on the cascaded dual-mode resonators and frequency transformation is also introduced. The surface current distributions are simulated to verify the performance of the proposed filter. The measured results show 2.14/4.33 GHz DB-BPF with 3-dB fractional bandwidth (FBW) of 0.27/0.15, respectively, which is suitable for WLAN applications. The return and insertion losses of the passband are better than 15/15-dB and less than 0.8/1.3-dB, respectively. The overall physical size of the fabricated DB-BPF is 20.4 mm × 20.4 mm, equivalent to 0.23λg × 0.23λg, where λg is the guided wavelength at 2.14 GHz. The simulation results are in good agreement with the measurement results.