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The results of investigating gas hydrate decomposition processes in model porous media using a Micro-CT Test System were analyzed. The objects of the study were natural gas hydrates produced at a specified pressure and temperature using porous media consisting of sand with three particle size ranges (0.85-1.18, 1.18-2.85, and 2.85-4.8 mm). The microstructural characteristics and the porosity of the obtained gas hydrates in the decomposition process were studied. The dependence of microstructural characteristics of gas hydrates on the nature of the porous medium, based on which the hydrates were produced, was also investigated. The results indicate that the hydrate is distributed uniformly and fills the pores of the porous media almost completely.

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

A novel compact dual-wideband bandpass filter (BPF), with two multi-mode resonators (MMRs), a quad-mode one (QMR) and a triple-mode one (TMR), is proposed in this paper. The first passband is generated by a QMR loaded with a short-ended stub and two open-ended stubs, and the second one is realized by a TMR loaded with a square ring and a short-ended stub. Each passband can be tuned separately by controlling the corresponding resonator. The classical even-/odd-mode analysis is applied to characterize the presented MMRs due to their symmetric configurations. In order to validate the design methodology, a dual-wideband BPF prototype centered at 2.34 and 3.46 GHz with fractional bandwidths of 25.6% and 21.4% for WLAN and WiMAX applications is designed, fabricated and measured. Measurements have good agreement with simulations.

In this paper, A novel compact co-planar waveguide (CPW)-fed tri-band antenna with dual band-notched characteristic is proposed. This antenna consists of a circular element, two inverted L-shaped slots, and a T-shaped slot etched into the circular element, which lead to the desired high attenuation at the two notch frequencies: 2.56 GHz – 3.25 GHz and 3.8 GHz – 4.96 GHz. The proposed tri-band antenna is CPW-fed and printed on an low-cost FR-4 substrate with only 20 mm × 28 mm surface area. The antenna is successfully simulated by the full-wave electromagnetic (EM) simulator HFSS and measured to cover the bandwidth for WLAN and WiMAX (2.40 GHz – 2.54 GHz, 3.24 GHz – 3.76 GHz, 4.96 GHz – 6.65 GHz) applications. Experimental results show that, the proposed tri-band antenna is obtained with promising performances, including omnidirectional radiation patterns and stable gains across its whole operation bands.

In this article, a novel compact triple-band monopole antenna for WLAN/WiMAX applications is proposed. The proposed antenna is designed on an FR-4 substrate with thickness of 0.8 mm, relative permittivity of 4.4 and loss tangent of 0.02. It consists of a square ring, an open ended stub, and an inverted T-shaped stub. Three bands covering 2.3-2.76, 3.387-3.73, and 4.97-6.28 GHz are achieved, which cover all the 2.5/3.5/5.5 GHz WiMAX and 2.4/5.2/5.8 GHz WLAN operation bands. Moreover, the presented antenna has a compact size of 24 × 36 mm 2 . Experimental results show that the proposed antenna gives good gains and has nearly omnidirectional radiation patterns across all the operation bands.

In this article, a novel miniaturized tri-band monopole antenna for WLAN/WiMAX applications is presented and investigated. The proposed antenna consists of a horizontal H-shaped patch, an L-shaped open end stub, and a deformed inverted T-shaped strip. The patch attached to the 50-› feed-line through a matching line can increase the bandwidth of the proposed antenna. The bandwidths under the condition of jS11j • i10dB of the proposed antenna are 340MHz (2.4{2.74GHz), 340MHz (3.41{3.75GHz), and 640MHz (5.24{5.88GHz), respectively, indicating this antenna is suitable for WLAN (2.45{2.4835, 5.16{5.35, and 5.725{5.85GHz) and WiMAX (2.5{2.69, 3.4{3.69, and 5.28{ 5.85GHz) applications. The antenna is successfully simulated and measured. Experimental results show that the proposed antenna with compact size of 30£20£0:8mm 3 has nearly omnidirectional radiation characteristics and stable gains across all the operating bands with a simple structure.

In this article, a compact dual-band bandpass filter (BPF) using coupled open-loop resonators and an embedded center-grounded stepped-impedance resonator (CGSIR) is proposed. This filter operates at 2.1/5.2 GHz for WCDMA/WLAN applications. The first passband is generated by the proposed CGSIR, and the second one is created by the coupled open-loop resonators. Each passband can be controlled independently by adjusting the dimension parameters of corresponding resonators. Five transmission zeros (TZs) are generated due to the 0 ◦ feed structure and signal cancellation effects between electric couplings and magnetic couplings, which improve the filter band-to-band isolation level and skirt selectivity significantly. Moreover, the overall circuit size is very compact due to the embedded configuration. The measured filter performances are in good agreement with the simulated ones.