This frequency band can be confirmed by the experimental results of transmission (S 21 ) phase of SSR and FR4, shown in Figure 7 where 6.92-7.14 GHz for SSR is noticed as frequency region in which transmission phase increases while decreases in the remaining frequencies like FR4. This increase of transmission phase shows that backward waves propagate in this frequency band.Because of negative group delay and propagation of backward waves, it is confirmed that SSR (of dimensions given in the caption of Fig. 3) behaves as LHM at 6.92-7.14GHz frequency band. COMPARISON OF ANALYTICAL AND EXPERIMENTAL RESULTSThe comparison of frequencies at which the permeability of SSR becomes negative, using analytical and experimental results is given in Table 1. In the experimental result, frequency band (where SSR acts as LHM), is included as permeability and permittivity both are negative in LHM. The analytical solution of SSR shows that SSR's permeability achieves negative value at 7.47GHz and the experimental results show LH frequency band at 6.92-7.14 GHz, i.e., SSR's permeability has negative value at 6.92-7.14 GHz according to the experimental results. So, the analytical and the experimental results of SSR are found in good agreement and the expression for the effective permeability of SSR, presented in this article, is verified. CONCLUSIONSA simple expression for the effective permeability of SSR is presented in this article. Experimental results are included for the verification of the analytical work. The results, obtained from both approaches, are found in good agreement. So, the analytical work presented in this article is verified and can be used to predict LH frequency band of SSR.ABSTRACT: A microstrip line ultra-wideband (UWB) bandpass filter with high performances using a pair of multiple-mode resonators (MMRs) is proposed in this letter. A pair of MMRs and aperture on background are adopted in the filter to tighten the coupling strength of inter-digital capacitor, and good impedance match is implemented by stepped impedance feeders so as to achieve high performances. Based on the design above, a UWB filter with high performances is simulated, fabricated, and measured. Simulated results show that the proposed filter has good UWB passband performances with insertion loss lower than 0.5 dB from 3.11 to 9.52 GHz and return loss higher than 20 dB from 3.28 to 10.36 GHz as well as group delay variation less than 0.1 ns. Good agreements are obtained between its measured and simulated results.
A dual band‐notched planar ultra‐wideband (UWB) monopole antenna using hybrid resonators is presented in this article. By etching a complementary electric‐LC resonator on the ground plane and a split ring resonator on the regular octagon radiation patch, dual band‐notched characteristics are achieved. Details of the antenna design, the radiation pattern and the measured results of voltage standing wave ratio (VSWR) are given. Experimental results demonstrate that the proposed antenna operates over a UWB frequency range from 2.9 to 12.4 GHz for VSWR < 2 while providing dual band‐stop function in the frequency bands of 3.3–3.6 and 5.2–5.8 GHz. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26033
A novel dual wideband and low cross‐polarization printed dipole antenna for wireless local area network applications is proposed in this article.Two H‐slots are etched symmetrically on the radiating arms which produce the dual band characteristic. By using the tapered U‐shaped structures, good wide band impendence matching can be achieved without additional matching circuit, and then dual wideband can be obtained conveniently. Based on this concept, a prototype of this antenna has been designed, fabricated, and measured. The experimental results show that the proposed antenna yields two operating bands of 2.17–2.95 GHz and 5.05–6.46 GHz with −10 dB return loss, which can cover all the wireless local area network operating bands. Moreover, the radiation patterns are almost omnidirectional in the H‐plane and low cross‐polarization levels are observed in both the E‐ and H‐plane. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2846–2848, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27173
frequencies using equivalent circuit model and THz-TDS system. We found that the structure could be used as a bandpass filter with narrow transmission band and very sharp edges in the terahertz wave region. Because of the charming features of compact size, easy fabrication, flexibility, and low fabrication cost, the terahertz wave filter based on the structure have been attracted much attention, and which will be crucial in the implementation of future terahertz communications systems.ABSTRACT: A novel printed dipole antenna for wireless local area networks (WLAN) applications is presented in this article. The proposed antenna, characterized by dual-band, low cross-polarization, and smallsize, consists of two asymmetric tapered arms. A novel feed scheme is employed to realize a balanced feed. For validation, the antenna prototype is fabricated and measured. The performance of the antenna is verified and characterized in terms of return loss, radiation pattern, and gain. The simulated and measured results show good agreement. Details of the proposed antenna design and tested results are presented and discussed.ABSTRACT: This article presents a high efficiency current-mode class-D (CMCD) amplifier using a GaN high electron mobility transistor (HEMT) for class-S system-a digitally controlled by deltasigma modulation. To enhance a drain efficiency of CMCD amplifier, the chip-on-board (COB) technique, which can reduce the external parasitic components of the packaged transistor and allow fast switching operation at high frequencies by minimizing distortion of the pulse waveform, is adopted. A LC-resonance circuit with adequate Q values between each transistor and output matching network controls harmonic signal by using the lumped elements to extract pure fundamental frequency of the output signal. For a high efficiency pushpull operation of CMCD amplifier, low-loss rat-race baluns are integrated at input and output circuits. From the measured results for a continuous wave of 3.35 GHz, the CMCD amplifier using COB technique shows a maximum output power of 35.88 dBm and a maximum power gain of about 10 dB. Also, the proposed CMCD amplifier provides a high power-added-efficiency (PAE) of 63.1% and a drain efficiency of 76.3% at maximum output power. The drain efficiency is still remained over 70% in the frequency range of 200 MHz.
Baicalein (BA), one of the major bioactive flavonoids isolated from Scutellariae Radix, possesses various pharmacological activities. The present study aimed to investigate the protective effects of BA on tert‑butyl hydroperoxide (t‑BHP)‑induced hepatotoxicity, and to investigate the potential mechanisms in LO2 cells. BA was demonstrated to possess protective properties against t‑BHP injury in LO2 cells, as evidenced by MTT and lactate dehydrogenase assays. BA significantly prevented t‑BHP‑induced depolarization of mitochondrial membrane potential (MMP), decreased the percentage of apoptotic cells caused by t‑BHP, and prevented intracellular reactive oxygen species (ROS) generation in LO2 cells. Furthermore, BA slightly triggered autophagy in LO2 cells, as evidenced by the elevation of LC3‑II expression, while BA combined treatment with an autophagy inhibitor (chloroquine) or activator (rapamycin) did not alter the hepatoprotective properties. In conclusion, BA may possess a hepatoprotective effect against t‑BHP‑induced liver cell injury, dependent on ROS removal. Therefore, BA may represent a potential drug candidate in protecting hepatotoxicity.
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