Guang-Ming Wang

A Miniaturized Triple-Band Branch-Line Coupler Based on Simplified Dual-Composite Right/Left-Handed Transmission Line

A miniaturized triple-band branch-line coupler based on the simplifled dual-composite right/left-handed transmission line (S-D-CRLH-TL) is proposed in this paper. The electromagnetic characteristics of S-D-CRLH-TL are analyzed by the simulator and equivalent circuit model, and the results prove that there are three frequency points with phase of i90-degree in the passbands; this characteristic can be used to design triple-band quadrature microwave components. The proposed branch-line coupler is fabricated and measured, the measured and simulated results are in good agreement with each other, showing that the triple-band operating at 3.06GHz, 4.00GHz and 5.54GHz, the useful bandwidths are 2.97GHz{3.16GHz, 3.82GHz{4.12GHz and 5.48GHz{5.67GHz. In addition, compared with the conventional branch-line coupler, the whole size of the proposed one is 17mm£14:4mm (0:173‚£0:147‚) (‚ is the wavelength in low frequency), it realizes a 73% size reduction. Moreover, compared with the triple-band branch-line coupler based on the double-Lorentz transmission line metamaterial, the proposed branch-line coupler is more efiective in the situation, which is sensitive to phase-changing, as the sign of phase difierence in the two outputs at the three frequency points keeps the same.

Novel microstrip left-handed resonator with dual notched bands and its application in miniaturized triple-band 3-dB power divider

A novel microstrip left-handed resonator (LHR) is proposed in this paper by embedding narrow central symmetric spiral lines in the rectangular gap of the main microstrip line. According to the EM simulated results, the proposed LHR has two narrow notched bands, which is produced by the magnetic resonance and sudden change of the effective permeability and effective permittivity; the phase characteristics of the proposed LHR show that there are two frequency points with −90-degree phase shift and one frequency point with +90-degree phase shift in the passbands. According to the electromagnetic characteristics of the proposed LHR, we use it to replace the 70.7 Ω transmission line of conventional Wilkinson power divider, and a compact triple-band 3-dB power divider is presented. After fabrication, the presented triple-band power divider is measured by using Anritsu ME7808A vector network analyzer, the measured and simulated results are in good agreement with each other, showing that, the fabricated power divider operating at 2.20, 3.40, and 7.50 GHz with bandwidths of 84.5, 35.8, and 15.2%; in the passbands, the return loss is better than 15 dB, the insertion loss is between 3.4 ± 0.2 dB, and the isolation between port 2 and 3 is better than 20 dB. Moreover, the out-of-band rejection among three operating bands is also very good, which benefits from the two narrow notched bands. Simultaneously, the effective area of the fabricated power divider is 0.121 λg by 0.116 λg (where λg is the guided wavelength at 2.20 GHz), about 55.2% relative to that of conventional one operating at 2.20 GHz. Besides, the presented power divider is uniplanar, and there is no defected ground structure or lumped element.

Novel Simplified Dual-Composite Right/Left-Handed Transmission Line and its Application in Bandpass Filter with Dual Notch Bands

In this article, a novel simplifled dual-composite right/left- handed transmission line (S-D-CRLH-TL) is proposed according to the theory of dual-composite right/left-handed transmission line. The electromagnetic characteristics of S-D-CRLH-TL are analyzed by simulator, and the results indicate that the proposed structure has two narrow stopbands; they can be controlled by changing the geometry parameters of the structure. Then, a bandpass fllter with dual notched bands is designed by using the unit cell of S-D-CRLH-TL, and the designed fllter is simulated, fabricated and measured, the measured and simulated results are in good agreement with each other, showing that the two notched bands centered at 3.60GHz and 5.50GHz, and the bandwidths are 9.7% and 7.3%. This designed fllter can avoid the interference to UWB communication system efiectively, which comes from the signals of WiMAX and WLAN. Besides, in comparison with the other bandpass fllter with notched-bands, the designed fllter has good electromagnetic performances.

Metamaterial beam scanning leaky-wave antenna based on quarter mode substrate integrated waveguide structure*

In this paper, we first propose a metamaterial structure by etching the same two interdigital fingers on the upper ground of quarter mode substrate integrated waveguide (QMSIW). The simulated results show that the proposed QMSIW-based metamaterial has a continuous phase constant changing from negative to positive values within its passband. A periodic leaky-wave antenna (LWA), which consists of 11 QMSIW-based metamaterial unit cells, is designed, fabricated, and measured. The measured results show that the fabricated antenna achieves a continuous beam scanning property from backward −43° to forward +32° over an operating frequencyrange of 8.9 GHz–11.8 GHz with return loss better than 10 dB. The measured antenna gain keeps consistent with the variation of less than 2 dB over the operating frequency range with a maximum gain of 12 dB. Besides, the measured and simulated results are in good agreement with each other, indicating the significance and effectiveness of this method.

Novel improved metamaterial transmission line and its application in wideband leaky-wave antenna with wide beam-scanning angle range and low cross-polarization

Abstract In this paper, a novel-improved metamaterial transmission line (MTM TL) is investigated and applied to design periodic leaky-wave antenna (LWA) with wide beam-scanning angle range and low cross-polarization. The improved MTM TL consists of metallic holes and interdigital fingers (which embedded in the main microstrip line). By introducing the metallic holes loaded in the interdigital fingers, the parasitic resonant modes of conventional MTM TL can be eliminated effectively. Considering the continuous phase constants changing from negative to positive values of the improved MTM TL under the balanced condition, a continuous beam-scanning property from backward to forward directions of the resultant periodic LWA can be obtained. For verification, a periodic LWA, which consists of 20 unit cells of the improved MTM TL, is fabricated and measured. The measured and simulated results are in good agreements with each other in all condition. According to the measured results, the fabricated periodic LWA operates from 3.38 to 4.60 GHz with a bandwidth of 30.57%, and achieves a continuous beam-scanning property from backward –65° to forward +71° (including broadside radiation) over the operating frequency band. Moreover, the measured cross-polarization remains at a level of more than 30 dB below the co-polarization across the entire radiation region. The presented LWA should find promising applications in modern wireless communication systems due to these wonderful electromagnetic performances.

Design of Compact Wideband Bandpass Filter with Good Performances Based on Novel CRLH Resonator

A novel miniaturized composite right/left-handed (CRLH) transmission line based on the structure of spiral inter-digital is proposed and analyzed in this article. Compared with the conventional inter-digital CRLH, the proposed CRLH realizes a 25% resonance frequency shift, and the miniaturization is realized. Then, a compact bandpass filter centered at 1.00 GHz with minimum insertion loss 0.42 dB was designed, fabricated and measured. The measured results show that the bandwidth is 61.6% and that the sharpness at the two edges of passband is 212.5 dB/GHz and 607.1 dB/GHz. This designed filter has very high selectivity. Besides, the whole size of the designed filter is 0.114λ×0.054λ. The filter realizes the miniaturization effectively, and this designed bandpass filter has good performances and smaller size than the same works in references.

Beam Scanning Antenna with Wideband Broadside Radiation Based on Multilayered Substrate Integrated Waveguide Composite Right/Left-Handed Structure

Abstract In this paper, a novel multilayered substrate integrated waveguide (SIW) composite right/left-handed (CRLH) structure is proposed to design beam scanning antenna for wideband broadside radiation. The unit cell of the SIW-CRLH structure is formed by spiral interdigital fingers etched on the upper ground of SIW, and a parasitic patch beneath the slot, has a continuous change of phase constant from negative to positive value within its passband. The proposed beam scanning antenna, which consists of consists of 15 identical elementary cells of the SIW-CRLH, is simulated, fabricated and measured. According to the measured results, the proposed antenna not only realizes a continuous main beam scanning from backward –78° to forward +80° within the operating frequency range from 8.25 to 12.2 GHz, but also obtains the measured broadside gain of 11.5 dB with variation of 1.0 dB over the frequency range of 8.8–9.25 GHz (4.99 %). Besides, compared with the same works in the references, this one has the most wonderful performance.