Jiuhuai Lei

Compact and High Selectivity Tri-Band Bandpass Filter Using Multimode Stepped-Impedance Resonator

In this letter, a miniaturized tri-band bandpass filter (BPF) using a multimode stepped-impedance resonator (SIR) with a 0 ° tapped-feed structure is presented. The odd- and even-mode fundamental resonant frequencies and the first high-order resonant frequencies of the SIR are utilized to generate dual-mode dual-band response and the tapped side-coupled feed-lines construct an additional passband avoiding occupying extra size. Owing to the 0 ° tapped-feed structure and the intrinsic characteristics of the SIR, multiple transmission zeros are created to improve the selectivity of the filter. The bands of the designed tri-band BPF are located at 1.57 GHz (GPS application), 3.5 GHz (WiMAX application) and 5.8 GHz (WLAN application). Good agreement between the simulated and the measured results is observed.

Compact Dual-Band Bandpass Filter Using Quadruple-Mode Square Ring Loaded Resonator (SRLR)

A compact quadruple-mode square ring loaded resonator (SRLR) is proposed in this letter. Distinct mode splitting characteristics of the quadruple-mode SRLR are investigated and explained by using even- and odd-mode analysis. It results to excite four resonant modes which are applied to produce two pairs of transmission poles for dual-band bandpass filter (BPF) design. Based on the unique characteristics of the proposed SRLR, a miniaturized dual-band BPF operating at 2.45 GHz and 5.20 GHz for WLAN applications was designed and fabricated. Multiple transmission zeros are generated to improve the selectivity of the filter. Measurements are in good agreement with the simulations. Also, the circuit size occupies only 0.11λg×0.23λg, where λg is the guided wavelength at the center frequency of the first passband.

Single-Feed Slotted Bowtie Antenna for Triband Applications

In this letter, a triband bowtie antenna for 3.5/4.5/5.8-GHz applications using slot technique is presented. The proposed microstrip-fed antenna forms operating frequencies by inserting two pairs of slots with different lengths on the isosceles triangle microstrip patch without increasing the overall antenna area. The size of the proposed antenna is determined by the middle resonant frequency f0, and thus it is compact in nature. The geometry of the bowtie antenna is symmetrical to the direction of the feedline. The proposed antenna is designed, analyzed, and verified by simulations and measurements.

Compact High-Temperature Superconducting Filter Using Multimode Stub-Loaded Resonator

A simple multimode resonator loaded by open- and short-end stubs is proposed in this paper. Its transmission characteristics and equivalent circuit models are investigated by even-odd mode analysis. In addition, the multiband filter design theory using the proposed resonator is explained, and the desired passbands can be conveniently allocated by properly choosing the dimension parameters of the stub-loaded resonator. For demonstration purposes, a compact high-temperature superconducting (HTS) filter operating at 1.57, 2.6, and 3.50 GHz is designed and fabricated. To sharpen the passband skirts of the filter, a source-load coupling configuration with interdigital structure is arranged to produce several transmission zeros. Then, multipath coupling diagrams are constructed, and the relative phase shifts of each path are studied to explain the responses of the triple-band filter. Furthermore, a grounding technique of the short-end stub is realized by subtly connecting with the metal wall packaging instead of via holes in the substrate. In consideration of the inaccuracy in HTS fabricating and packaging, an optimization scheme is proposed. The results of the sensitivity analysis revealed that the optimization scheme is viable. Finally, measurements are in good agreement with the electromagnetic simulations and verify the circuit design methodology.

Compact Triple-Band High-Temperature Superconducting Filter Using Multimode Stub-Loaded Resonator for ISM, WiMAX, and WLAN Applications

A compact triple-band high-temperature superconducting (HTS) bandpass filter using multimode stub-loaded resonator is proposed in this paper. The resonant characteristics of the multimode resonator are investigated by the even/odd-mode analysis. To sharpen the passband skirts, a source-load coupling configuration with a nonresonant node is arranged to produce several extra transmission zeros for realizing high-selectivity performances. For demonstration purposes, a triple-band filter operating at 2.45 GHz (ISM band), 3.5 GHz (WiMAX band), and 5.2 GHz (WLAN band) is designed, fabricated, and measured. Measurements are in good agreement with the electromagnetic simulations. The measured minimum insertion losses of the triple-band HTS filter are 0.16, 0.55, and 0.22 dB, whereas the return losses are greater than 16.7, 10.2, and 17.5 dB, respectively. Its overall size is only 8.3 mm

Compact Tri-Band Bandpass Filter Using Quintuple-Mode Stub-Loaded Resonator

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Observation of tunable nonlinear effects in an analogue of superconducting composite right/left hand filter

8.6 mm.

Compact quad-band superconducting metamaterial filter based on split ring resonator

Abstract A miniaturized tri-band bandpass filter using a quintuple-mode stub-loaded resonator and a folded half-wavelength resonator is presented. The characteristics of the quintuple-mode resonator are investigated by using even- and odd-mode analysis, generating tri-band response. By adding a half-wavelength resonator, the bandwidth of the second passband can be controlled easily. Three passbands of the filter are designed at 1.8, 2.4, and 3.5 GHz for global system for mobile communication, wireless local area networks, and worldwide interoperability for microwave access applications. The center frequencies of the three passbands can be independently controlled, and their bandwidths can be tuned properly by controlling the dimension parameters of the filter. In addition, six transmission zeroes are produced to improve the selectivity of this filter. Measured results have good agreement with simulations.

A Miniaturized Dual-Mode Bandpass Filter Using Slot Spurline Technique

Artificial structures with negative permittivity or permeability have attracted significant attention in the science community because they provide a pathway for obtaining exotic electromagnetic properties not found in natural materials. At the moment, the great challenge of these artificial structures in microwave frequency exhibits a relatively large loss. It is well-known that superconducting thin films have extremely low surface resistance. Hence, it is a good candidate to resolve this constraint. Besides, the reported artificial structures with negative permittivity or permeability are mainly focusing on linear regime of wave propagation. However, any future effort in creating tunable structures would require knowledge of nonlinear properties. In this work, a tunable superconducting filter with composite right/left-hand transmission property is proposed and fabricated. Its nonlinear effects on temperature and power are studied by theoretical analysis and experiments.

Microstrip tri-band bandpass filter using dissimilar stepped-impedance-resonator with controllable multiple transmission zeros

In this Letter, a multi-resonant split ring resonator (SRR) is proposed for multi-band application. Its equivalent circuit model and even/odd-mode analysis are investigated. To verify this design methodology, a quad-band high-temperature superconducting (HTS) metamaterial structure is designed and fabricated with a compact size of 11.1 mm × 14.95 mm (about 0.149 λ g by 0.2 λ g). The insertion losses at each passband are 0.13, 0.07, 0.135, and 0.2 dB, respectively. The temperature effects and power handling capability of the quad-band HTS filter are also studied and the results show that the device has both perfect quad-band bandpass performance (temperature 100 K) for the multi-band communication and superconductor switch applications.