Home About us Contact
|
Home About us Contact | ||
|
|
||
RF Power (rf + power)
Selected AbstractsA method of accurate determination of azimuthal distribution of received RF powerINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 2 2001A. A. Alexandridis Abstract In this paper, we introduce a method for the determination of directional distribution of received RF power, with angular resolution independent of receiving antenna radiation pattern. The proposed method is based on a series of measurements taken while rotating, at fixed predefined steps, a usual directional antenna of known radiation pattern on the azimuthal plain. It is proved that the resolution accuracy of the measurement method depends only on the angular step of the antenna rotation and it is independent of the antenna beamwidth. As a result of this feature, the proposed method allows the determination of the RF power angular distribution with fine resolution using a directional antenna of much wider beamwidth for the measurements. Copyright © 2001 John Wiley & Sons, Ltd. [source] VHF high-power tunable RF bandpass filter using microelectromechanical (MEM) microrelaysINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 5 2001Robert D. Streeter Abstract A VHF RF bandpass filter tuned through the use of MEM microrelays was operated at a 25 W RF power input level. The filter insertion loss was less than 1 dB at the tuned frequencies of operation, and the filter operating Q was about 10. The MEM microrelays were life tested for 53 million operating cycles at 25 W RF power, and no significant degradation to the contacts was noted. The development of the microrelay and the use of a CAE tool in the filter development are discussed. © 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE 11: 261,275, 2001. [source] Plasma-induced graft polymerization of poly(ethylene glycol) on poly(methyl methacrylate) surfaces for improving antistatic propertyJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2010Yanlin Wei Abstract Ar plasma-induced graft polymerization of poly(ethylene glycol) (PEG) on Ar plasma pretreated poly(methyl methacrylate) (PMMA) surfaces was carried out to improve the antistatic properties. The surface composition and microstructure of the PEG-grafted PMMA surfaces from plasma induction were characterized by attenuated total reflectance Fourier transfer infrared (ATR-FTIR) spectroscopy, water contact angles (CA), and atomic force microscopy (AFM) measurements. The measurements revealed that the antistatic properties can be remarkably improved with the surface resistivity of PEG-grafted PMMA surface decreasing significantly by 3,6 orders of magnitude, with the optimum condition for polymerization grafted onto the Ar plasma pretreated PMMA surface being 40 W for RF power and 3 min for glow discharge time. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Gold-Tip Electrodes,A New "Deep Lesion" Technology for Catheter Ablation?JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 7 2005In Vitro Comparison of a Gold Alloy Versus Platinum, Iridium Tip Electrode Ablation Catheter Radiofrequency (RF) catheter ablation is widely used to induce focal myocardial necrosis using the effect of resistive heating through high-frequency current delivery. It is current standard to limit the target tissue,electrode interface temperature to a maximum of 60,70°C to avoid char formation. Gold (Au) exhibits a thermal conductivity of nearly four times greater than platinum (Pt,Ir) (3.17 W/cm Kelvin vs 0.716 W/cm Kelvin), it was therefore hypothesized that RF ablation using a gold electrode would create broader and deeper lesions as a result of a better heat conduction from the tissue,electrode interface and additional cooling of the gold electrode by "heat loss" to the intracardiac blood. Both mechanisms would allow applying more RF power to the tissue before the electrode,tissue interface temperature limit is reached. To test this hypothesis, we performed in vitro isolated liver and pig heart investigations comparing lesion depths of a new Au-alloy-tip electrode to standard Pt,Ir electrode material. Mean lesion depth in liver tissue for Pt,Ir was 4.33 ± 0.45 mm (n = 60) whereas Au electrode was able to achieve significantly deeper lesions (5.86 ± 0.37 mm [n = 60; P < 0.001]). The mean power delivered using Pt,Ir was 6.95 ± 2.41 W whereas Au tip electrode delivered 9.64 ± 3.78 W indicating a statistically significant difference (P < 0.05). In vitro pig heart tissue Au ablation (n = 20) increased significantly the lesion depth (Au: 4.85 ± 1.01 mm, Pt,Ir: 2.96 ± 0.81 mm, n = 20; P < 0.001). Au tip electrode again applied significantly more power (P < 0.001). Gold-tip electrode catheters were able to induce deeper lesions using RF ablation in vitro as compared to Pt,Ir tip electrode material. In liver and in pig heart tissue, the increase in lesion depth was associated with a significant increase in the average power applied with the gold electrode at the same level of electrode,tissue temperature as compared to platinum material. [source] An experimental load matching technique for RF CMOS power amplifierMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2008YunSeong Eo Abstract A load matching method for CMOS PA (power amplifier) design is proposed. The contours for RF power and efficiency can be drawn while considering external L and C as tunable X and Y variables. On the basis of the existence of this contour, the realization of load matching of CMOS PA is easily achieved and optimized. A tested CMOS PA based on 0.18 ,m CMOS technology shows a design example whose P1dB is 17.8 dBm and power efficiency 37%, respectively. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 899,902, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23248 [source] Spectral shaping of acousto-optic tunable filter: A method to tune the bandwidth, wavelength, and attenuationMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2006S. Veeriah Abstract In this article, we presented a method, which will allow multiple parameter control of the 3-dB bandwidth, centre-notch wavelength, and attenuation level in a fiber-based acousto-optic tunable filter. The method basically involves the variation of the interaction length, RF frequency, and RF power on a single fiber device, to achieve multiple parameter tuning of the optical filter. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1781,1785, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21783 [source] Steerable Sheath Catheter Navigation for Ablation of Atrial Fibrillation: A Case-Control StudyPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 7 2008CHRISTOPHER PIORKOWSKI M.D. Background: Lack of stable access to all desired ablation target sites is one of the limitations for efficacious circumferential left atrial (LA) pulmonary vein (PV) ablation. Targeting that, new catheter navigation technologies have been developed. The aim of this study was to describe atrial fibrillation (AF) mapping and ablation using manually controlled steerable sheath catheter navigation and to compare it against an ablation approach with a nonsteerable sheath. Methods and Results: In this case-control-analysis 245 consecutive patients (controls) treated with circumferential left atrial PV ablation were matched with 105 subsequently consecutive patients (cases) ablated with a similar line concept but mapping and ablation performed with a manually controlled steerable sheath. One hundred sixty-six patients were selected to be included into 83 matched patient pairs. Ablation success was measured with serial 7-day Holter electrocardiograms. Patients ablated with the steerable sheath showed an increase in the success rate (freedom from AF) from 56% to 77% (P = 0.009) after a single procedure and 6 months of follow-up. With respect to procedural data no difference could be found for procedure time, fluoroscopy time, irradiation dose, and radiofrequency (RF) burning time. With the steerable sheath mean procedural RF power (33 ± 9 vs 41 ± 4 W; P < 0.0005) and total RF energy delivery (97,498 vs 111,864 J; P < 0.005) were significantly lower and the rate of complete PV isolation significantly increased from 10% to 52% (P < 0.0005). The complication rate was the same in both groups. Among different arrhythmia, procedure, and patient characteristics, the lack of early postinterventional arrhythmia recurrences was the only but powerful predictor for long-term ablation success. Conclusions: An AF mapping and ablation approach solely using a manually controlled steerable sheath for catheter navigation improved the outcome of circumferential left atrial PV ablation at similar intervention times and similar complication rates. The 6-month success rate after a single LA intervention increased from 56% to 77%. [source] Plasmas for texturing, cleaning, and deposition: towards a one pump down process for heterojunction solar cellsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010Mario Moreno Abstract Low temperature plasma deposition of a-Si:H thin films has emerged as a promising alternative for high efficiency hetero junction (HJ) solar cells. In this work we study plasma processes for texturing and cleaning c-Si wafers pursuing a low cost dry fabrication process of HJ solar cells. We have studied two independent plasma processes: i) Texturing of c-Si wafers using SF6 - O2 plasmas in a RIE system, in order to reduce the surface reflectance and therefore improve the light trapping. The effects of the RF power and gas ratio on the c-Si surface texture have been studied in detail. Highly textured surfaces, with very low reflectance values (around 6% in the range of 300 , 1000 nm) have been achieved. ii) Etching of the native oxide and passivation of the c-Si surface by plasma, in a standard RF PECVD system. We used SiF4 plasma with optimized conditions for an efficient native oxide removal, and without breaking the vacuum, 40 nm of a-Si:H were deposited in order to passivate the c-Si surface. High effective lifetime values were obtained (,eff , 1.5 ms), providing high implicit open circuit voltages (Voc , 0.713 V) and low surface recombination velocities (Seff < 9 cm s -1). (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] AlGaN/GaN dual-gate high electron mobility transistors on SiC substrates for high-power mixersPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2005K. Shiojima Abstract We have demonstrated dual-gate AlGaN/GaN high-electron-mobility transistors on SiC substrates for high-power mixers and examined DC and up-conversion RF measurements with drain-source bias voltages (VDS) to analyze the possible output level. The 0.7 × 300 µm-gate device exhibited the maximum transconductance of 47 mS, maximum RF power of 19.6 dBm and up-conversion gain of 11 dB at 2 GHz when VDS = 15 V. For VDS of over 15 V, the devices occasionally broke down, because, although the device can handle more drain current, but the voltage swing reached the breakdown voltage of about 30 V. These results indicate that a Watt-class output mixer can be easily achieved with this simple dual-gate structure. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Rotational and Vibrational Temperature Measurements in a High-Pressure Cylindrical Dielectric Barrier Discharge (C-DBD)CONTRIBUTIONS TO PLASMA PHYSICS, Issue 1 2005N. Masoud Abstract The rotational (TR) and vibrational (Tv) temperatures of N2 molecules were measured in a high-pressure cylindrical dielectric barrier discharge (C-DBD) source in Ne with trace amounts (0.02 %) of N2 and dry air excited by radio-frequency (rf) power. Both TR and Tv of the N2 molecules in the C 3,u state were determined from an emission spectroscopic analysis the 2nd positive system (C 3,u , B3,g). Gas temperatures were inferred from the measured rotational temperatures. As a function of pressure, the rotational temperature is essentially constant at about 360 K in the range from 200 Torr to 600 Torr (at 30W rf power) and increases slightly with increasing rf power at constant pressure. As one would expect, vibrational temperature measurements revealed significantly higher temperatures. The vibrational temperature decreases with pressure from 3030 K at 200 Torr to 2270 K at 600 Torr (at 30 W rf power). As a function of rf power, the vibrational temperature increases from 2520 K at 20 W to 2940 K at 60 W (at 400 Torr). Both TR and Tv also show a dependence on the excitation frequency at the two frequencies that we studied, 400 kHz and 13.56 MHz. Adding trace amounts of air instead of N2 to the Ne in the discharge resulted in higher TR and Tv values and in a different pressure dependence of the rotational and vibrational temperatures. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Efficient low-power heteronuclear decoupling in 13C high-resolution solid-state NMR under fast magic angle spinningMAGNETIC RESONANCE IN CHEMISTRY, Issue S1 2007Mrignayani Kotecha Abstract The use of a low-power two-pulse phase modulation (TPPM) sequence is proposed for efficient 1H radio frequency (rf) decoupling in high-resolution 13C solid-state NMR (SSNMR) under fast MAS conditions. Decoupling efficiency for different low-power decoupling sequences such as continuous-wave (cw), TPPM, XiX, and ,-pulse (PIPS) train decoupling has been investigated at a spinning speed of 40 kHz for 13C CPMAS spectra of uniformly 13C - and 15N -labeled L -alanine. It was found that the TPPM decoupling sequence, which was originally designed for high-power decoupling, provides the best decoupling efficiency at low power among all the low-power decoupling sequences examined here. Optimum performance of the low-power TPPM sequence was found to be obtained at a decoupling field intensity (,1) of ,,R/4 with a pulse flip angle of ,, and a phase alternation between ± ,(, = ,20° ), where ,R/2, is the spinning speed. The sensitivity obtained for 13CO2,, 13CH, and 13CH3 in L -alanine under low-power TPPM at ,1/2, of 10 kHz was only 5,15% less than that under high-power TPPM at ,1/2, of 200 kHz, despite the fact that only 0.25% of the rf power was required in low-power TPPM. Analysis of the 13CH2 signals for uniformly 13C- and 15N-labeled L -isoleucine under various low-power decoupling sequences also confirmed superior performance of the low-power TPPM sequence, although the intensity obtained by low-power TPPM was 61% of that obtained by high-power TPPM. 13C CPMAS spectra of 13C -labeled ubiquitin micro crystals obtained by low-power TPPM demonstrates that the low-power TPPM sequence is a practical option that provides excellent resolution and sensitivity in 13C SSNMR for hydrated proteins. Copyright © 2007 John Wiley & Sons, Ltd. [source] Characterizations of nanostructured silicon-carbon films deposited on p-layer by PECVDPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010U. Coscia Abstract Nanostructured silicon carbon films composed of silicon nanocrystallites embedded in the amorphous silicon carbon matrix are prepared by a rf-PECVD system at 250 °C from silane and methane gas mixture highly diluted in hydrogen onto 7059 Corning glass and p-layer deposited on tin oxide substrates by varying rf power from 25 to 65 W. The structural and compositional properties of the films have been investigated. The study demonstrates that rf power controls the crystalline fraction as well as the silicon crystallite size and that p-layer/tin oxide structure enhances the nucleation of silicon grains as compared to Corning glass (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Nanocrystallites formation in a-SiC by low power plasma enhanced chemical vapour depositionPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010Ayana Bhaduri Abstract Formation of nanocrystallites in the amorphous silicon carbide thin films deposited from silane methane mixture diluted in argon by plasma enhanced CVD has been studied under different levels of rf power density and Ar dilution. Systematic transformations between different polymorphic phases of SiC have been observed with changes in rf power and Ar dilution. At low Ar dilution no H-SiC (,-SiC) nanocrystallites was observed. Only traces of ,-SiC of Si were observed. With increase in Ar dilution formation of ,-SiC nanocrystallites was observed. Increase of rf power density at this dilution enhanced ,-SiC nanocrystallites but reduced ,-SiC slightly. Variation of SiC peak in the infra red absorption corresponds closely with the changes in ,-SiC nanocrystallites in the layers. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Reactive ion etching of dielectrics and silicon for photovoltaic applicationsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 7 2006Prakash N. K. Deenapanray Abstract This paper investigates the reactive ion etching of SiO2, Si3N4, and Si using CHF3/O2 plasma. In particular, we have characterized the time and rf power dependence of the carrier lifetimes in n- and p-type FZ Si. The time dependence of reactive ion etching (RIE) at different rf powers provide insight into the two competing processes of damage accumulation and damage removal in the near-surface region of the Si during plasma etching. The carrier lifetime, measured using the quasi-steady-state photoconductance (QSSPC) technique, has a quadratic dependence on the rf power, which can be related to changes in the dc self-bias generated by the plasma at different rf powers. The change in carrier lifetime is similar in both n- and p-type Si of the same doping concentration. Using this fact, together with the electronic properties of defects obtained by deep level transient spectroscopy (DLTS), we have modeled the injection-dependence of the measured carrier lifetimes using the Shockley,Read,Hall model. The isochronal annealing behavior of plasma etched Si has also been studied. Copyright © 2006 John Wiley & Sons, Ltd. [source] | ||||||||||||||||