Open-loop Stepped-impedance Resonator Research Articles

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

<abstract><p>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.</p></abstract>

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.

High‐conductivity graphene‐assembled film‐based bandpass filter for 5G applications

This article presents a compact 5G dual-wideband bandpass filter (DBPF) based on high-conductivity graphene assembled films (GAFs), which can meet the requirements of the sub-6 GHz bands, high integration and high information transmission rate for 5G wireless communication. The GAF DBPF consists of two folded open-loop stepped-impedance resonators with a compact size of 21.9 mm × 22.5 mm × 0.53 mm. The measured results show that the presented GAF DBPF has two passbands with 3 dB fractional bandwidths of 15.95% and 12.72% at center frequencies of 2.14 and 3.5 GHz, respectively. In addition, the filter exhibits an attenuation level greater than 20 dB up to 7.52 GHz.

Dual-/Tri-Wideband Bandpass Filter with High Selectivity and Adjustable Passband for 5G Mid-Band Mobile Communications

The design and implementation of the filters for the fifth-generation (5G) mobile communication systems are challengeable due to the demands of high integration, low-cost, and high-speed data transmission. In this paper, a dual-wideband bandpass filter (BPF) and a tri-wideband BPF for 5G mobile communications are proposed. The dual-wideband BPF consists of two folded open-loop stepped-impedance resonators (FOLSIRs), and the tri-wideband BPF is designed by placing a pair of folded uniform impedance resonator inside the dual-wideband BPF with little increase in the physical size of the filter. By employing a novel structural deformation of a stepped-impedance resonator, the FOLSIR is achieved with a more compact structure, a controllable transmission zero, and an adjustable resonant frequency. The measurement results show that the working bands of the two filters are 1.98–2.28/3.27–3.66 GHz and 2.035–2.305/3.31–3.71/4.54–5.18 GHz, respectively, which are consistent with the full-wave EM simulation results. The implemented filters have a compact size and the results show low loss, good out-of-band rejection, and wide passbands covering sub-6 GHz bands of 5G mobile communications and a commonly used spectrum.

Design of a Dual-Mode Tunable Wide-Bandstop Filter with Controllable Bandwidth

In this article, a compact dual-mode tunable wide bandstop filter with controllable bandwidth is presented. The proposed filter consists of an open-loop stepped-impedance resonator with a T open stub loaded. Varactor diodes Cv1 and Cv2 are loaded at two ends of the stepped-impedance resonator and the loaded T stub, respectively. By properly adjusting the capacitances Cv1 and Cv2 of the varactor diodes, the constant fractional bandwidth and constant absolute bandwidth can be achieved, respectively. A new dual-mode tunable wide bandstop filter with 61.0% constant fractional bandwidth and 2.0-GHz constant absolute bandwidth has been designed and fabricated to verify the validity of the proposed method. The measured results are in good agreement with the electromagnetic simulation.

Wide upper-stopband microstrip bandpass filter with dual-mode open loop stepped-impedance resonator and source-load coupling structure

In this article, a dual-mode microstrip bandpass filter (BPF) with compact size, sharp skirt, and wide upper-stopband performance is proposed using the short-stub-loaded open loop stepped-impedance resonator and source-load coupling structure. The advantageous features of the resonator are that the even-mode resonant frequencies can be controlled exclusively by the short stub, and two transmission zeros are created near the passband by the short stub and the folded arms. Meanwhile, two transmission zeros generated by the source-load coupling structure can be applied to suppress the first and second spurious harmonics. Finally, a microstrip BPF located at 2.4 GHz with a fractional bandwidth 4% is designed, fabricated, and measured. The upper stopband in experiment is extended up to 20 GHz with an insertion loss lower than −21.2 dB. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1618–1621, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26881

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.

Design of a novel HTS open‐loop SIR filter with the relocation of its second passband

AbstractThis paper presents a novel open‐loop stepped impedance resonator (OLSIR), which has advantage of compact structure and its relocatable first spurious frequency. A four‐pole high temperature superconducting (HTS) filter made up of OLSIRs is designed and fabricated'and the measurement result has good agreement with the simulation. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2097–2101, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22685