Quarter-wavelength Stepped-impedance Resonators Research Articles

A novel self‐packaged DBBPF with multiple TZs for 5G sub‐6 GHz applications

AbstractIn this article, we proposed a self‐packaged dual‐band bandpass filter (DBBPF) with high isolation and low insertion loss (IL) for 5G sub‐6 GHz applications. To get high stopband suppression, multiple and controllable transmission zeros (TZs) are introduced. A pair of quarter‐wavelength stepped‐impedance resonators (QSIRs) and half‐wavelength hairpin resonators (HWHR) are introduced to form a cross‐coupled five‐star topology to generate two passbands and multiple TZs analyzed by mixed electromagnetic couplings. A pair of U‐shape resonators are designed on G6 to fully excite the resonators and introduce source/load TZs at the same time. The generation of TZs by separate electric and magnetic coupling paths (SEMCP) is discussed. The DBBPF achieves a low IL of 0.85/1.13 dB with fractional bandwidths (FBW) of 11.0%/6.9% at center frequencies of 3.45 and 4.9 GHz for 5G sub‐6 GHz applications, respectively. The total size is only 0.32 λg × 0.45 λg.

High-Selectivity Bandpass Filter with Controllable Attenuation Based on Graphene Nanoplates.

A high-selectivity band pass filter with controllable attenuation based on graphene nanoplates is proposed in this paper. Graphene with controllable resistance has a good uniform attenuation effect to electric field intensity. The filter utilizes quarter wavelength stepped impedance resonators and mixed electromagnetic coupling to have compact circuits and high performance. The graphene nanoplates are loaded on the microstrip resonator to reduce the electric field intensity, which results in a flat attenuation in the passband. In addition, the filter has two transmission zeros, which lead to a strong selectivity. Finally, a high-selectivity bandpass filter with controllable attenuation is formed. By changing the bias voltage of graphene, a controllable attenuation of 1.64–11.13 dB can be achieved in the working passband centered at 1.36 GHz. In order to validate the concept, the prototype is fabricated and measured. The measurement results are in good agreement with the simulation results. The proposed high-selectivity bandpass filter with controllable attenuation based on graphene nanoplates has widely potential in reconfigurable wireless communication systems and radar systems due to its high integration and versatility.

350-GHz Bandpass Filters Using Superconducting Coplanar Waveguide

On-chip filters play an invaluable role in most detectors and instruments, blocking unwanted, harmonic, or mirrored signals. In this article, two coplanar waveguide bandpass filters working at 350 GHz are designed based on quarter-wavelength stepped impedance resonators, which can be easily integrated in on-chip systems. A second-order filter with a classical Chebyshev response and a fourth-order filter with quasi-elliptical characteristic is developed together to define the roll-off performance. Both filters are patterned based on superconducting niobium film by the optical lithography and lift-off process, which could reduce the significant metallic loss in high terahertz band. All the chips integrated with transitions are evaluated through a quasi-optical system, which is built based on the sensitive superconductor-insulator-superconductor tunnel junction detector at cryogenic temperature. The calibrated transmission responses, which are matched with simulations, have indicated that such superconducting coplanar waveguide filters can be enabled in future terahertz astronomical spectrometer.

Design of a Compact SISL BPF With SEMCP for 5G Sub-6 GHz Bands

In this letter, a cross-coupled dual-bandpass filter (BPF) with separate electric and magnetic coupling paths (SEMCPs) for 5G sub-6 GHz applications is proposed. Source-to-load couplings are also introduced in this structure for the flexibility of heterogeneous feed lines. Five controllable transmission zeros (TZs) in total are produced in the dual-band filter. The filter achieves good overall performance by adopting two pairs of quarter-wavelength stepped-impedance resonators (SIRs). To minimize the size of the filter and enlarge the controllable range of the second passband, the SIRs forming the second passband are separated and folded onto two different layers. The measured dual band filter achieves fractional bandwidths of 7.82% and 4.08%, centered at frequencies of 3.45 and 4.9 GHz with insertion losses of 1.15 and 1.42 dB, respectively.

A Miniaturized Wideband Bandpass Filter Using Quarter-Wavelength Stepped-Impedance Resonators

In this paper, we present a simple method to design a miniaturized wideband bandpass filter with suppression of the third harmonic, using only two quarter-wavelength stepped-impedance resonators (SIRs). The resonant modes of the quarter-wavelength SIR, depending on the impedance ratio (K) and electrical length ratio (α), are discussed first. As to setting the resonant frequency of the SIR for the lower band edge of the required band, the size parameters of two quarter-wavelength SIRs can be determined by selecting the desired impedance ratio (K) and length ratio (α). By using the opposite directional arrangement of two SIRs with direct taped input/output ports, the wideband response can be formed. A filter example is shown in this study to address this simple design procedure. The measured results of the fabricated filter have a wide passband response from 3.3 to 5.8 GHz, with an insertion loss of 1.5 dB, a return loss of 20 dB, an extended bandwidth ration of 55%, a low-average group delay of less than 0.75 ns, and a stopband from 6 to 12 GHz, with an attenuation level of 20 dB. Due to the similar 0° feeding, a transmission zero at 8.3 GHz appears near the band edge; thus, improving the band selectivity. The proposed filter can have a very simple structure and a miniature size. Simulated results and measured results are in good agreement.

A Filtering Power Divider with Tunable Center Frequency and Wide Stopband

AbstractIn this paper, a tunable power divider (PD) with a good band-pass filtering response using quarter-wavelength stepped impedance resonators (SIRs) is presented. By appropriately adjusting the impedance and electrical length ratio of SIR, the proposed structure can achieve wide stopband performance. Meanwhile, four varactor diodes are loaded to the external resonators to achieve electrical reconfiguration. In addition, a pair of transmission zeros (TZs) can be generated by applying source and load coupling on each side of the passband, which can effectively improve passband selectivity and out-of-band rejection. In order to verify the feasibility of the proposed design method, a prototype circuit of the proposed filtering power divider (FPD) with tunable center frequency is simulated, fabricated and measured. A good agreement between the simulation and measurement results is observed.

Miniature dual‐band bandpass filter using modified quarter‐wavelength SIRs with controllable passbands

A modified quarter-wavelength ( λ /4) stepped-impedance resonator (SIR) is proposed to design a miniature dual-band bandpass filter (BPF). The proposed λ /4 SIR has two individually controllable resonances for constructing dual passbands. Moreover, two independent geometrical parameters are adopted to realise individual adjustment of the coupling strengths between two adjacent λ /4 SIRs at the dual passbands. As a result, both the centre frequencies and bandwidths of the two passbands of the filter can be individually designed. Furthermore, multiple transmission zeros are created by the introduced source-load coupling, which improves highly the selectivity of both passbands. The dual-band BPF is designed at 2.35 and 5.8 GHz, and its simulated and measured responses are presented and show good agreement.

In brief

PAGE 43 A novel scheme for the production of an optical frequency comb with high flatness for many spectral lines has been proposed by researchers in Korea. Experimental results demonstrate the scheme shows perfect spectral profiles with some lines having less than 1 dB flatness when applying a dual-parallel modulator. PAGE 38 A project from researchers in Japan and China has produced a modified quarter-wavelength stepped impedance resonator for use in the design of a miniature dual-band bandpass filter. The resulting device allows the center frequencies and bandwidths of the two passbands to be individually controlled, with source-load coupling producing multiple transmission zeros to improve selectivity. Proposed comb generation scheme. PAGE 12 Researchers from New Zealand, Australia, and the USA have demonstrated the performance of Rivener, a mask-less oral and nasal audio recorder and air-flow estimation system. The setup allows for clinical observation of vocal recordings whilst minimally impeding the speaker and consistently differentiating medium and high nasalance passages. Configuration of the proposed dual-band BPF. PAGE 51 Complicated motion error in synthetic aperture radar (SAR) has been analysed and a precise frequency-division algorithm is proposed to compensate for the residual aperture-variant motion. The method, produced by a group of researchers in China, can be integrated with traditional image formation algorithms. Photograph of Rivener headset. PAGE 18 The structure of a three-axis gimbal for a hexacopter UAV is optimised to improve the accuracy of a 720° panoramic shot camera array. The system, implemented by researchers in China, includes a non-contact magnetic encoder which forms part of the closed-loop controls to minimise the shake performance of the system. Enlarged view of selected CSA integrated image. The principle structure of the three-axis gimbal.

Miniaturized Bandpass Filter with Wide Stopband using Spiral Configuration of Stepped Impedance Resonator

Abstract In this letter, a miniaturized Band Pass Filter (BPF) with wide stopband centered at 0.350 GHz for TETRA band applications is proposed using a Spiral Short Circuit quarter wavelength Stepped Impedance Resonator (SSC-SIR) and a stub loaded on feed line for enhancement of rejection level in the stopband. Spiral configuration of the resonator is used for the miniaturization of BPF. The proposed BPF provides a 3dB fractional bandwidth of 13.7 % with two transmission zeros in the lower and upper stopband to provide good selectivity and four transmission zeros which provide wide stopband upto 6.86f0. Proposed BPF has a very compact size of 0.064λg×0.062λg.

Compact Multi-Layer Bandpass Filter With Wide Stopband Using Selective Feeding Scheme

This brief presents a new approach for designing compact bandpass filters (BPFs) with harmonic suppression using quarter-wavelength stepped-impedance resonators (SIRs). The voltage-null point of the third harmonic on the SIR is theoretically derived and found for the first time. It is used as the exciting location for the selective feeding line so that the third harmonic cannot be excited and is suppressed successfully in the filter design. Meanwhile, the passband of the BPF operating at the fundamental resonant frequency ( ${f_{ 1 }}$ ) of the SIR can be optimized and obtained by tuning other parameters. By combining the proposed simple technique and the SIR merits, the resultant BPF owns several advantages, such as wide stopband and miniaturization. To demonstrate the feasibility of the proposed idea, two design examples of second-/fourth-order BPFs based on multilayer PCB are designed. In both designs, the third harmonic suppression is larger than 30 dB and the first spurious occurs at a frequency beyond ${7f_{ 1 } }$ . Their simulated and measured results are presented, showing good agreement.

A wideband bandpass filter with multi-mode resonator and mixed electromagnetic coupling

In this paper, a wideband bandpass filter using multi-mode resonator and mixed electromagnetic (EM) coupling is presented. To increase the bandwidth while not enlarge the circuit size, multi-short-stub multi-mode resonator, which produces multiple resonances, is utilized. Furthermore, the capacitive gap between open ends of the stubs is utilized to realize electric coupling between the multi-mode resonator and quarter-wavelength stepped impedance resonator. Meanwhile, a high-impedance transmission line between them is used to implement magnetic coupling. This mixed EM coupling can produce transmission zero near the passband, consequently improving the frequency selectivity of proposed filter. Measured results of the filter prototype are in good agreement with the simulated ones. The filter is with an insertion loss at central frequency of 15.86 GHz about 2.5 dB, a 3 dB bandwidth about 5.72 GHz (the fractional bandwidth about 36%), and the variation of group delay over the whole passband <0.28 ns. Additionally, the effective circuit size of the filter is about 0.126 λg2, where λg is the wavelength of 15.86 GHz. All these results have shown that proposed filter is promising for future high-precision imaging system or high-speed communication application.

Compact dual‐band microstrip filtering power divider using T‐junction structure and quarter‐wavelength SIR

This Letter presents a design of microstrip filtering power divider for dual-band application. The proposed dual-band filtering power divider is based on the traditional Wilkinson power divider and employs T-junction structures and quarter-wavelength stepped impedance resonators (SIRs) to realise dual-band power allocation and bandpass response simultaneously. The design process is simple and effective. For validation, a dual-band microstrip filtering power divider with centre frequencies of 0.9 and 2.1 GHz for the GSM and WCDMA applications is designed, fabricated and measured. The measured results indicate that the proposed dual-band filtering power divider showcases low-loss characteristics, high isolation as well as good selectivity.

Compact Bandpass Filter With Multiple Coupling Paths in Limited Space for Ku-Band Application

A compact bandpass filter (BPF) for Ku-band application is proposed in this letter. The proposed filter is composed of five quarter-wavelength ( $\boldsymbol {\lambda }{/4}$ ) stepped-impedance resonators, which are in staggered arrangement. Folded narrow feedlines are used to introduce multiple coupling paths in limited space. Two symmetrical cascaded quadruplet like (CQ-like) structures are formed and devoted to generate two transmission zeros (TZs) located in both the upper and lower sides of the center frequency $(f_{{\mathbf {0}}})$ . Two other TZs are generated by the coupling path between folded narrow feedlines. Two TZs in upper rejection band can be adjusted to special locations to strength the suppression in these points. A prototype of the proposed filter was fabricated and good agreement between simulation and measurement is achieved. The proposed BPF owns the advantages of high selectivity, compact size, low insertion loss, and low cost.

Design of Compact Six-Channel Diplexer

Compact six-channel diplexer (1.575/2.4/5.2 GHz and 1.8/3.5/5.8 GHz) using multipath quarter wavelength stepped impedance resonators (SIRs) is proposed. The sixchannel diplexer includes two pairs of magnetically coupled SIRs by grounded via hole. The resonant frequencies of each channel can be easily determined by changing the impedance ratio (K) and length ratio ( $\alpha $ ) of SIRs. The diplexer provides the advantages of effective design method, low loss, high passband selectivity, compact circuit size, and very useful for applying on the multi-band wireless communication systems.

Design of Single- and Dual-Band Power Dividers Integrated Filtering Responses Based on SIRs

Abstract In this paper, two single- and dual-band equal power dividers (PDs) integrated filtering responses are proposed using quarter-wavelength stepped-impedance resonators (SIRs). By appropriately adjusting the impedances and electric length ratios of SIRs, the proposed structures can achieve compact sizes and wide stop-band performances. In addition, source-load coupling is applied to create a pair of transmission zeros at each side of the pass-bands, which can improve effectively the frequency selectivity and the out-of-band rejection. To validate the design theory, two single- and dual-band PDs with good filtering responses are designed, implemented and measured, respectively. The predicted results on S parameters are compared with the measured ones and good agreement is achieved.

Dual‐band bandpass Wilkinson power divider of controllable bandwidths

In this reported work, quarter-wavelength stepped-impedance resonators with K inverters have been employed to realise a dual-band bandpass Wilkinson power divider (WPD). The individual bandwidth of each passband can be controlled with the dualband resonators and K inverters. A systematic design approach of the power divider is provided with the aid of the even-odd mode analysis and verified by circuit simulation. A 2.45/5.8 GHz WPD with a Chebyshev response has also been implemented for validation. The measured fractional bandwidth of 20 dB return loss (1/| S 11 |) is 7.0%/4.1% which is consistent with the theoretical design. In addition to the 3 dB power division, an insertion loss of 0.8/1.2 dB is obtained. Isolation of 20.1/19 dB at the centre frequency is also achieved. Full-wave simulated data are also presented and show good agreement with measured results. Compared with other dual-band bandpass power dividers, the proposed circuit exhibits better impedance matching and bandwidth.

Design of novel compact dual-band filtering power divider using stepped-impedance resonators with high selectivity

A novel compact dual-band power divider with filtering responses is presented in this article. The proposed circuit utilizes coupled quarter-wavelength stepped-impedance resonators. By controlling these resonators, dual-band operation can be realized. Furthermore, a resistor is connected between the two open ends of the input feed line to obtain good isolation at two bands. Source load coupling is utilized to enhance the selectivity. To verify the proposed idea, a filtering power divider with the operating frequencies of 2.4 and 5.8 GHz is implemented. Good agreement between the simulated and measured results validates the proposed idea. The total size of the circuit is 0.23λg × 0.28λg, where λg is the guide wavelength of 2.4 GHz. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:262–267, 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

DUAL-BAND BANDPASS FILTER WITH WIDE UPPER STOPBAND USING NOVEL STEPPED IMPEDANCE STUB-LOADED QUAD-MODE RESONATOR

This paper presents a wide upper stopband dual-band bandpass filter (BPF) with controllable passband frequencies and bandwidths as well as a high out-of-band rejection level. The proposed filter is realized by utilizing a novel stepped impedance stub-loaded quad-mode resonator. All the four-mode equivalent circuits of the resonator are quarter-wavelength stepped impedance resonators (SIRs), and their fundamental resonance frequencies are used to form the passbands, so the designed filter has a compact circuit size. By controlling the impedance and length ratios of the stubs of the resonator, wide upper stopband performance is obtained. Hook-shape feed-lines and source-load coupling are applied to provide appropriate external coupling and generate three extra transmission zeros, which greatly improve the selectivity of the proposed filter. An experimental filter operating at 1.5 and 3.5 GHz is designed, fabricated, and measured for validation. The measured results have good agreement with the simulated ones.