Radio Frequency Input Power Research Articles

Lead phthalocyanine films deposited by ECR plasma-induced sublimation

Lead phthalocyanine (PbPc) thin films deposited by vacuum sublimation with Ar low-temperature electron cyclotron resonance (ECR) plasma treatment are investigated by means of reflection high-energy electron diffraction, atomic force microscopy, infrared spectroscopy, x-ray photoelectron spectroscopy and spectral ellipsometry. The intensity of plasma treatment is varied by the radio-frequency power input and the value of electrical bias applied to the sample. The films grown with and without plasma assistance are compared. The plasma intensity is considered to significantly influence the crystalline structure, surface morphology and film composition. At a low intensity the plasma assistance is analogous to vacuum annealing of films. At a medium intensity, a porous polymer matrix filled with PbPc in crystalline phases (monoclinic and triclinic) is formed in the films. At a high intensity, all the films consist of a compact polymer matrix, similar to a glassy solid, with small inclusions of PbPc molecules. The succession of PbPc molecule destructions in the growing film layer with plasma intensity increase is established by IR spectroscopy. The mechanism of polymer matrix formation is suggested.

32-$\mu{\rm W}$ Wirelessly-Powered Sensor Platform With a 2-m Range

In this paper, the experimental results of a complete battery-less wirelessly-powered 2.45-GHz temperature sensor system with a microcontroller (μC) and an ISM-band transmitter on FR-4 is presented. As the measured results show, the energy harvesting system can provide 2.4 V to turn on the μC , temperature sensor and transmitter with only -15 dBm (32μW) radio frequency input power and up to 0.2°C temperature resolution. The system is able to transmit 32-bit sensor data back to the base station with an extra 16 bits for cyclic redundancy check check at regular intervals. The battery-less μC can be wirelessly powered when located up to a distance of 2 m from a power transmitter supplying less than 50 mW of microwave power using a patch array.

An experimental study of the plasma parameters of a hybrid low-pressure RF discharge

This paper presents an experimental study of the plasma parameters of a hybrid radio-frequency (RF) discharge, which is a new modification of an RF discharge. The discharge is maintained by both vortex and potential RF electrical fields. To generate a hybrid RF discharge, an RF power input unit is used in the form of a parallel-connected inductor and capacitor coatings. A blocking capacitor is included in the capacitive channel of the discharge. The paper presents data from the study of the influence of power coupled to the plasma, argon pressure, and blocking capacitance on the plasma parameters, i.e., the electron energy distribution, temperature, and density and plasma potential. The role of the capacitive channel in the variations in properties and the characteristics of the discharge are considered.

Superconducting RF Metamaterials Made With Magnetically Active Planar Spirals

Superconducting metamaterials combine the advantages of low-loss, large inductance (with the addition of kinetic inductance), and extreme tunability compared to their normal metal counterparts. Therefore, they allow realization of compact designs operating at low frequencies. We have recently developed radio frequency (RF) metamaterials with a high loaded quality factor and an electrical size as small as $\sim$$\lambda$658, ($\lambda$ is the free space wavelength) by using Nb thin films. The RF metamaterial is composed of truly planar spirals patterned with lithographic techniques. Linear transmission characteristics of these metamaterials show robust Lorentzian resonant peaks in the sub- 100 MHz frequency range below the $T_c$ of Nb. Though Nb is a non-magnetic material, the circulating currents in the spirals generated by RF signals produce a strong magnetic response, which can be tuned sensitively either by temperature or magnetic field thanks to the superconducting nature of the design. We have also observed strong nonlinearity and meta-stable jumps in the transmission data with increasing RF input power until the Nb is driven into the normal state. We discuss the factors modifying the induced magnetic response from single and 1-D arrays of spirals in the light of numerical simulations.

Performance characterization of a helicon double layer thruster using direct thrust measurements

The performance of a helicon double layer thruster (HDLT) has been characterized using a pendulum type thrust stand and retarding field energy analyser. Data recorded for a fixed propellant flow rate of 16 sccm of krypton and fixed magnetic field topology show that the thrust generated increases linearly with increasing radio frequency input power over a range 250–650 W. Over the power range investigated thrust levels of approximately 1–2.8 mN were achieved. A maximum effective specific impulse of 280 s was determined using the thrust data. Ion energy distribution functions indicate that increasing power corresponds to improved plasma generation processes as general trends show increasing plasma and beam currents with increasing power.

Characteristics of hydrogen production of an Enterobacter aerogenes mutant generated by a new atmospheric and room temperature plasma (ARTP)

A novel atmospheric and room temperature plasma (ARTP) which used helium as the working gas was employed to generate mutants of Enterobacter aerogenes for improving the hydrogen production. For the mutation, 50 μl of the E. aerogenes culture (OD 600 = 2.0) was dipped onto a sterilized stainless steel plate (5 mm in diameter). The plate was then treated for 3 min by ARTP at the gas flow rate of 15.0 slpm (standard liters per minute) and 100 W of radio-frequency power input. The positive mutation rate defined by the ratio of the mutants with the increase of hydrogen productivity to the total mutants reached about 10%, and a mutant with improved cell growth and hydrogen productivity was then selected. The total hydrogen yield per mole glucose was increased by 26.4%, mainly dependent on the increase of hydrogen production by the NADH pathway. Two important parameters of the ATP yield and oxidation state balance indicated that the cellular metabolism was changed in the mutant. The genetic stability of the mutant for hydrogen production was maintained after more than 25 subcultures.

DOUBLE AND TRIPLE LANGMUIR PROBES MEASUREMENTS IN INDUCTIVELY COUPLED NITROGEN PLASMA

The double and triple Langmuir probe diagnostic systems with their necessary driving circuits are developed successfully for the characterization of laboratory built low pressure inductively coupled nitrogen plasma, generated by 13.56MHz radio frequency (RF) power supply along with an automatic impedance matching network. Using the DC properties of these two probes, the discharge plasma parameters like ion saturation current (Iio), electron temperature (kTe) and electron number density (ne) are measured at the input RF power ranging from 250 to 400W and fllling gas pressures ranging from 0.3 to 0.6mbar. An increasing trend is observed in kTe and ne with the increase of input RF power at a flxed fllling gas pressure of 0.3mbar, while a decreasing trend is observed in kTe and ne with the increase of fllling gas pressure at a flxed input RF power of 250W.

Ultra-efficient microwave harvesting system for battery-less micropower microcontroller platform

The experimental results of a micro-powered 2.45 GHz voltage multiplier with and without the charge-pump integrated circuit (IC) driving a microcontroller on FR-4 are presented. Five different rectifier designs are built and compared under different input power levels. Results show that a multi-stage voltage multiplier delivers higher voltage levels to the microcontroller without the need for the charge-pump IC. However, a single-diode design performs best when the charge-pump IC is present. The measurement results show that the energy harvesting system can provide 2 V to turn on the microcontroller with only −15.6 dBm (27.5 µW) radio frequency input power and that the battery-less microcontroller can be wirelessly powered when located up to a distance of 57 cm from a transmitter supplying a total of just 100 mW of microwave power.

DESIGN OF A MICROSTRIP BALANCED MIXER FOR SATELLITE COMMUNICATION

The design and measured results of a compact, low cost, low conversion loss microstrip single balanced Schottky diodes mixer is proposed. This mixer is designed for Ka-band satellite transponder simulator to convert the 30GHz radio-frequency (RF) signal down to the 20GHz intermediate-frequency (IF) signal with 9.8GHz local oscillator (LO) frequency. This design takes full advantage of the frequency relationship of the RF, IF and LO, which is 3 : 2 : 1. A microstrip rat-race ring is designed at the LO frequency, which also functions as a 180-degree hybrid coupler at the RF frequency by its intrinsic multi-band characteristic. The amplitude and phase balance at both LO and RF frequency are analyzed, which guarantee the state- of-art performance of this single balanced mixer. The multi-function open/short stubs and a lowpass fllter (LPF) with bonding wires across the rat-race ring are optimized to realize this low conversion loss mixer. The measured results show that the conversion loss is less than 9dB at the IF frequency from 20.0 to 21.6GHz, and the power of the second harmonic of LO is i45dBm with +6:5dBm LO drive power. The 3rd order inter-modulation products (IMD3) could be lower than i50dBc with LO power higher than +7:8dBm at the input RF power of i15dBm.

Effect of hydrogen plasma treatment on reduction process of iron oxide nanoparticles

Fe3O4 nanoparticles coated with oleic acid as a surfactant were reduced by hydrogen plasma generated by 13.56 MHz Radio-Frequency (RF). With increasing input RF power to the inductive coil, Fe3O4 nanoparticles could be transformed to almost single phase of Fe3C and finally to α-Fe. The average grain sizes of Fe3C and α-Fe nanoparticles are 19 – 23 nm and 52 -59 nm, respectively. Saturation magnetizations of Fe3C and α-Fe nanoparticles at 5 K were almost same as these of bulk Fe3C and α-Fe. Field cooling procedure from room temperature to 5 K in the magnetic measurement revealed a formation of FeO phase from Fe3O4 by weak reduction. The desired ranges of electron temperature and electron density in order to obtain Fe3C and α-Fe phases were determined by investigating plasma characteristics.

Reducing SAR and enhancing cerebral signal‐to‐noise ratio with high permittivity padding at 3 T

Previous works have shown that placement of a high-dielectric pad can improve image intensity in a region adjacent to the pad, or that placement of dielectric pads around a large surface of the head can improve image homogeneity on an entire plane through the head in high-field MRI. Here, experimental results show that use of high-dielectric pads around the human head can reduce the required input radiofrequency power by 50% while enhancing image signal-to-noise ratio by 20-40% throughout the cerebrum at 3 T. Thus, dielectric pads may be used to provide a relatively simple and low-cost method for improving quality and safety of MRI in a variety of applications at 3 T.

SOME OBSERVATIONS FROM STUDIES OF RF PLASMA PYROLYSIS OF WASTE TIRES

Pyrolysis treatment of waste tires was studied in a capacitively-coupled radio frequency (RF) plasma reactor. Using RF input power between 1600 and 2000 W and a reactor pressure between 3000 and 8000 Pa, a reactive plasma environment with a temperature between 1200 and 1800 K can be reached. Under these conditions, pyrolysis experiments with tire powder showed that two product streams were obtained: a combustible gas and a pyrolytic char. The main gaseous components were H2, CO, and CH4. When adopting double sets of electrodes in this plasma reactor, the gas yield and concentrations of H2 and CO can be enhanced. The energy utilization efficiency of this RF plasma pyrolysis reactor system was also analyzed.

Deposition of silicon oxide hard coatings by low‐temperature radio‐frequency plasmas

AbstractIn this study, the deposition of silicon oxide (SiOx) hard coatings on polycarbonate (PC) substrates was attempted with low‐temperature radio‐frequency (RF) plasmas from tetramethyldisiloxane (TMDSO) with the addition of oxygen. The coating uniformity and deposition rate were investigated in terms of substrate size, glow uniformity, and RF power input. The hardness of the resulting SiOx plasma coatings was examined by the ASTM pencil hardness test method. The hardness of the resulting SiOx plasma coatings was mainly determined by the TMDSO–O2 ratio in the plasma gas mixture. Ultraviolet–visible transmission spectra showed that these plasma coatings were transparent in the visible light region. Fourier transform infrared–attenuated total reflection analysis results indicated that the resulting SiOx plasma coatings were inorganic in nature. The interfacial adhesion, which is a common problem in the deposition of hard protective coatings on polymeric substrates, was also significantly improved by the deposition of an ultrathin plasma polymer interlayer from TMDSO before the deposition of the SiOx plasma coatings on the PC substrates. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Study of Optoelectronic Sampler Linearity for Analog-to-Digital Conversion of RF Signals

Photoconductive sampling of 10-GHz radio- frequency (RF) signal is demonstrated using interdigitated photoswitches made from low-temperature grown GaAs. We study the linearity of the device for RF input power ranging from -3 to 20 dBm. For moderate levels, the sampler shows a spurious-free dynamic range (SFDR) better than 40 dB. For the largest values, it exhibits a nonlinear response that deteriorates both SFDR and resolution. This nonlinearity is attributed to drift velocity saturation in the semiconductor material.

Stable Poly(Acrylic Acid) Films from Acrylic Acid/Argon Plasmas: Influence of the Mixture Composition and the Reactor Geometry on the Thin Films Chemical Structures

Thin films from acrylic acid and Ar mixtures were deposited on polypropylene films, aluminum foils and silicon 100 wafers by radiofrequency (RF) plasma polymerization. Different deposition conditions were investigated, varying the gas-mixture feed composition and the reactor geometry. For every tested condition, stable coatings (as assessed by long time immersion in phosphate buffer saline) were obtained by varying the RF power input. The influence of the gas carrier on the layer stability was discussed. The films were further characterized by water contact angle measurements, attenuated total reflectance infrared spectroscopy, X-ray photoelectron spectroscopy and atomic force microscope. Moreover, retention of carboxylic acid groups in the stable layers were investigated by means of ion-exchange reaction with thionin acetate. Results show a strong influence of the gas feed composition and the reactor geometry on the chemical structure of the deposited coatings, especially in their carboxylic groups concentration.

Nonlinear instability dynamics in a high-density, high-beta plasma

Entrainment and periodic pulling of an ion acoustic instability have been observed in the power spectra of a low-pressure high-beta plasma. The observed nonlinear phenomena can be modeled by using the van der Pol equation with a forcing term. Experimental results of the nonlinear processes are presented. Ion density fluctuations are detected on a negatively biased Langmuir probe for magnetic fields and input powers above 30 G and 900 W at 7.2 MHz respectively, and gas pressure below 1.5 mTorr. This low-frequency instability is observed in the central plasma blue core (argon II emission) and can be controlled by amplitude modulation of the radio frequency input power at frequencies close to the instability frequency.

A Wideband Power Detection System Optimized for the UWB Spectrum

A wideband radio-frequency (RF) power detection system is presented. The detection technique uses NMOS devices operating in the triode regime to generate an average current proportional to RF input power; this current is converted to voltage and amplified using a piecewise linear logarithmic approximation. Optimization of the NMOS devices is discussed, and a method of gain control is proposed for compensation of temperature and process variation. The power detector occupies an active area of 0.36 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> in a 0.18 mum CMOS process and consumes 10.8 mW from the power supply. Error between the output and a linear-in-dB best-fit curve is plusmn2.4 dB for a 20 dB input range, when measured at discrete frequencies. The output response is frequency independent, varying by less than 1.8 dB for a fixed input power as frequency is swept across the UWB spectrum.

Characterization of thin TiO 2 films prepared by plasma enhanced chemical vapour deposition for optical and photocatalytic applications

Thin titanium oxide films were deposited using a radio frequency (RF) plasma enhanced chemical vapour deposition method. Their optical properties and thickness were determined by means of ultraviolet–visible absorption spectrophotometry. Films of the optical parameters very close to those of titanium dioxide have been obtained at the high RF power input. Their optical quality is high enough to allow for their use in a construction of stack interference optical filters. At the same time, these materials exhibit strong photocatalytic effects. The results of structural analysis, carried out by Raman Shift Spectroscopy, show that the coatings posses amorphous structure. However, Raman spectra of the same films subjected to thermal annealing at 450 °C disclose an appearance of a crystalline form, namely that of anatase. Surface morphology of the films has also been characterized by Atomic Force Microscopy revealing granular, broccoli-like topography of the films.

Study on Radio Frequency Cathode for Ion Engines

A new cathode with inductively coupled plasma for ion engines was designed and then evaluated experimentally in this study. The fabricated cathode, which named “ICP/C (Inductively Coupled Plasma Cathode)”, employed electromagnetic fields induced by RF (Radio Frequency) current at 13.56 MHz, and had the new ignition method that spark discharge occurred by induced voltage was used. Through the experimental investigations, the new method using “C-shaped” type electrode enabled the ICP/C to ignite instantaneously without other electron source. And the cathode achieved high neutralization performance, which was over 1700 mA of extracted electron current at 80 W of RF input power, and 3.0 sccm of Xe flow rate, when target voltage simulating ion beam was 20 V. Additionally, the application of ICP/C as a main cathode of direct current ion thruster was confirmed. As these results, ICP/C may permit instantaneous ignition and simple handling to ion engines, and it may even allow a longer lifetime of ion engines.

Pyrolysis treatment of waste tire powder in a capacitively coupled RF plasma reactor

A capacitively coupled radio-frequency (RF) plasma reactor was tested mainly for the purpose of solid waste treatment. It was found that using a RF input power between 1600 and 2000 W and a reactor pressure between 3000 and 8000 Pa (absolute pressure), a reactive plasma environment with a gas temperature between 1200 and 1800 K can be reached in this lab scale reactor. Under these conditions, pyrolysis of tire powder gave two product streams: a combustible gas and a pyrolytic char. The major components of the gas product are H 2, CO, CH 4, and CO 2 The physical properties (surface area, porosity, and particle morphology) as well as chemical properties (elemental composition, heating value, and surface functional groups) of the pyrolytic char has also been examined.