RF Power Levels Research Articles

UNCERTAINTY EVALUATION USING LAW OF PROPAGATION AND MONTE CARLO SIMULATION METHODS WITH THE AUTORFPOWER MEASUREMENT SOFTWARE

RF power measurement is essential in RF and microwave metrology. For reliable and accurate power measurement, automatic measurement is preferred. A software application in C#, named AutoRFPower, was developed for automatic RF power measurement and uncertainty calculations at this study. According to the GUM document, this application is enhanced for uncertainty calculations by utilizing the Law of Propagation method and the Monte Carlo Simulation method. Trial measurements were performed at different RF power levels and frequencies between 50 MHz and 18 GHz using the AutoRFPower software. Law of Propagation and Monte Carlo Simulation uncertainty calculations were carried out by AutoRFPower based on the trial measurements and by the Oracle Crystal Ball simulation application. All measurements and their uncertainty calculations were compared with each other, and this study validated the uncertainty calculation of AutoRFPower. In addition, it was observed that in the Monte Carlo Simulation, uncertainty calculation results were non-symmetrical normal distribution, contrary to the assumption of symmetrical normal distribution according to the Low of Propagation method. Moreover, it has been observed that the statistical distribution of uncertainty changes depending on the dominant component of the parameters in the model function used for the uncertainty calculation with the Monte Carlo Simulation method.

Design and implementation of RF power levels measurement system from indoor to outdoor in Isparta province

This paper presents a novel, low-cost, and portable RF power measurement system, operating in GSM 900 and GSM 1800 frequency bands. This measurement model consists of four basic circuits; microstrip folded dipole antenna (MFDA) that received the ambient RF signals, a power meter that generates DC output voltage according to received RF signal power level, a microprocessor that converts the data's analog to digital, and a computer to record and screen the time-varying data. Seventeen measurements, each for six hours, were performed in nine locations in Isparta for the indoor-to-outdoor scenario. The range between the minimum and maximum power values of the average RF power levels obtained in time-dependent measurements was calculated as approximately 15 dB, 18 dB, and 33 dB for indoor, semi-indoor, and outdoor ambients, respectively. The indoor/semi-indoor/outdoor ambient RF power levels were respectively varied between −55.1 dBm to −4.13 dBm, −43.92 dBm to −6.12 dBm, −44.89 dBm to 0.1 dBm in all measurements.

H− Ion Source RF Plasma Testing with 13 MHz and 27 MHz at the Spallation Neutron Source (SNS)1

The baseline RF-driven H− ion source configuration at the Spallation Neutron Source (SNS) facility uses a continuous wave (CW) 600 W 13 MHz RF system to ignite and maintain a low-density plasma inside the ion source vacuum chamber. After the continuous low-density 13 MHz plasma has been established, a pulsed (typical 1 ms pulse width and 60 Hz pulse repetition rate) 80 kW 2 MHz RF system is used to increase the plasma density to produce the pulsed H− ion beam. Incremental upgrades and improvements to the SNS ion source systems have resulted in the ability to reliably operate an H− ion source for SNS neutron production run cycles that can last up to four months. Conditions inside the SNS H− ion source evolve throughout a four-month run cycle due to changes in impurity levels, sputtering, and erosion. As the internal ion source conditions change during the run cycle, there can also be changes in plasma stability and the 13 MHz RF power level required to ignite the plasma. This paper presents the preliminary results of testing performed on the SNS Ion Source Test Stand (ISTS) system where we looked at plasma ignition and plasma stability using 27 MHz RF in place of the baseline 13 MHz RF system.

Electromagnetic Waves’ Impact on Hydraulic Conductivity of Granular Soils

Electromagnetic (EM) waves, traditionally used for purposes such as geophysical characterization, impact properties to be measured. This paper describes the effects of radio frequency (RF) waves on the hydraulic conductivity of glass beads and natural sand. A series of tests was conducted using a customized, rigid-wall, cylindrical permeameter inside a resonant cavity made of Plexiglas covered with electrically conductive transparent films. Constant-head ASTM-D2434 tests were performed to measure the samples’ hydraulic conductivity. RF stimulation was performed using a magnetically coupled loop antenna at various frequencies and input RF-power levels. The hydraulic conductivity of both natural sand and glass-bead samples increased with RF stimulation. Furthermore, the measurement of the electric field component of RF waves was also performed to illustrate the pattern of the electric field, as well as evaluate RF’s impact on the hydraulic conductivity tests. The electric field was numerically simulated and validated against experimentally measured electric fields. A finite-difference numerical model was developed in MATLAB to analyze the seepage flow, which was then validated against the experimental results. An optimization scheme was then used to develop a governing equation for RF’s impact on hydraulic conductivity.

Technical design of an IH-type buncher for KoBRA at RAON

To satisfy the beam requirement of the KoBRA experiment (0.5 nsec in 1σ), rebunching is required in the energy range up to 15 A MeV and for particles with an A/q range from 1 to 7. In cooperation with IBS and Hanmac Corporation, BEVATECH proposed a five-gap IH-buncher cavity which has excellent bunching properties from 5 to 15 MeV/u. Main challenges in this project are the wide energy range and CW operation at RF power levels up to 20 kW. The cavity will offer an effective voltage amplitude of up to 1 MV. To provide the required cooling channels and cooling efficiency, the stems and drifttubes of this cavity will be 3D printed. This paper will discuss the technical design approach and give a status on the development of the buncher cavity.

Physics design, fabrication, RF measurement and beam commissioning of a dual beam drift tube linac

A novel type dual-beam drift tube linac (DB-DTL) prototype was firstly designed to prove the feasibility of the multi-beam type DTL at the institute of modern physics. The physics design, cavity fabrication, low-power RF measurement, RF conditioning and beam commissioning of the DB-DTL cavity were completed and presented in this paper. Operating at 81.25 MHz, the DB-DTL was designed to accelerate 10 mA proton from 0.56 MeV to 2.5 MeV. The field distribution of the DB-DTL cavity were measured at low RF power level and particle tracing using measured field were done, which both agree well with the physics design. The measured Q 0 value and the shunt impedance are 11606 and 172 MΩ/m, respectively. The RF conditioning and the first beam commissioning of the DB-DTL cavity were completed. The beam experiment platform was built at the Lanzhou university due to the academy research cooperation between the institute of modern physics, Sun Yat-sen university and Lanzhou university. Based on the existing experiment condition, 2.5 MeV proton acceleration and measurement were successfully achieved at 42 kW (0.85*Q 0)) RF power of the DB-DTL cavity, which match the physics design very well.

Physics design, construction and commissioning of the ICRH system for the stellarator Wendelstein 7-X

The ICRH antenna for the stellarator Wendelstein 7-X (W7-X) aims at delivering RF power levels up to about 1.5 MW in the frequency range 25–38 MHz with pulse lengths up to 10 s. The antenna was constructed and tested in the institute IEK-4 of the Research Centre Jülich, and subsequently installed at W7-X. The paper will review the physics design, the construction and installation in W7-X, and the commissioning plans for the ICRH system in the coming months.

Design and Prototyping of a Low-Cost High Frequency Antenna for Vicinity Coupling Devices

This paper describes the development of a high frequency (HF) antenna for high output power vicinity coupling devices (VCDs) operating at 13.56 MHz. Key design parameters, such as RF power level, antenna size, and communication protocol, and their link to the antenna features and requirements, have been discussed. For efficient reader interrogation, detection, and recovery of transponder responses, a tuning circuit necessary to adjust the antenna power matching and resonance characteristics was designed and prototyped. The antenna was fed to an industry standard reader and evaluated for read range performance with vicinity cards. The designed antenna on the reader achieved a good read range, which demonstrated fair agreement with the calculated theoretical results.

Reducing the β-Ga2O3 Epitaxy Temperature to 240 °C via Atomic Layer Plasma Processing

In this work, we report on low-temperature as-grown single-phase epitaxial beta-gallium oxide (β-Ga2O3) films on c-plane sapphire at the substrate temperature of 240 °C using plasma-enhanced atomic layer deposition (PEALD). The films were deposited using triethylgallium (TEG) and Ar/O2 plasma as the metal precursor and oxygen co-reactant, respectively. Growth experiments were performed with an rf-power level of 50 W. Additionally, each unit ALD cycle was followed by in situ Ar-plasma annealing treatment, which consisted of Ar-plasma exposure for 20 s at 250 W rf power. X-ray diffraction (XRD) of the sample on sapphire revealed epitaxial Ga2O3 film signature with the monoclinic β-phase. On the other hand, GIXRD of the samples grown on Si and glass displayed polycrystalline β-Ga2O3 films. High-resolution transmission electron microscopy (HR-TEM) confirmed the epitaxial relationship of the Ga2O3 layers grown on sapphire substrates. X-ray photoelectron spectroscopy (XPS) shed light on the chemical bonding states of pure β-Ga2O3 layers outlining the Ga–O bonding states. STEM-EDX measurements confirmed the pristine nature of the β-Ga2O3 film with carbon atomic composition falling below the tool’s detection levels.

Radiofrequency Energy Harvesting Systems for Internet of Things Applications: A Comprehensive Overview of Design Issues

Radiofrequency energy harvesting (RF-EH) solutions have evolved significantly in recent years due to the ubiquity of electromagnetic waves in any environment. This review presents a comprehensive report on autonomous wireless sensor (WS) design considerations based on RF-EH. The obtainability of RF-EH-WS is driven by development efforts in the areas of RF-EH circuit design, known as rectifying antenna (Rectenna), the minimization of the energy budget of WS (MEB-WS), and finally, power management modules (PMM). The PMM aims to optimize the energy efficiency of the WS. In addition to these three factors, examining the RF power levels harvested related to the rectenna feeding technique (RFT) is essential. Since we did not find any review presenting a holistic view of these design considerations, we strived to provide a detailed picture of recent advances and new enhancements in this review. To address this issue, this review gives an overview of the seminal and contemporary studies in the RF-EH-WS field. The IoT issues are also discussed in terms of their basic requirement to support reduced size or miniaturized smart objects, which are common matters in current applications of WS nodes. Potential open issues that might be considered for future research are also discussed in this article. For a more detailed description of all presented concepts, many significant references are provided for the readers.

Transition between monoclinic and tetragonal β phases induced by reactive oxygen gas in RF-sputtered V2O5 thin films

Thin films of V2O5 are promising materials for applications in chromogenic devices, such as gas sensors and contactless optical thermal sensors. Therefore, controlling the formation of the various phases of V2O5 is important. The device performance, in relation to satisfactory coloration efficiency and fast response, strongly depends on the characteristics of the phase incorporated in the film structure. To better understand the phase formation in these films, thin films of V2O5 were deposited by RF magnetron sputtering using an O2-reaction technique from a metallic V target, and the influence of RF power and O2 levels on the transition between the β-monoclinic and β-tetragonal phase structures was investigated by X-ray diffractometer. The films were also evaluated using Auger-electron, Raman-, and UV-vis spectrometers to determine their composition, chemical, and electronic properties to assess the effects of the two sputtering parameters. The mechanism underlying the development of film properties is related to the plasma characteristics and species observed by optical emission spectroscopy. Increasing the RF power resulted in a higher phase content of the β-monoclinic and α-orthorhombic phase, whereas an increasing the oxygen levels induced a phase transition towards the β-tetragonal phase of V2O5. Films with different phase contents exhibited different optical energy bandgaps. Plasma diagnostics showed that increasing the RF power increased the thickness of plasma sheaths on the target surface. The thinner sheath on the target surface further increased the β-tetragonal phase content. The variation between β-monoclinic and β-tetragonal phase content was expected because of the bombardment of energetic O− ions that were accelerated from the plasma sheath toward the growth surface. A deeper understanding of the transition between β phases in V2O5 films can enable better phase control, which can improve film application towards various sensing devices, particularly chromic- or temperature-sensors.

Oxygen plasma cleaning of copper for photocathode applications: A MEIS and XPS study

MEIS and XPS studies have been conducted for a range of oxygen plasma treated copper samples (and one treated with Ar plasma), as part of a study of the preparation of photocathode surfaces. This procedure was seen to remove hydrocarbon contamination, but left an oxide film whose thickness depended on the treatment conditions used. The film thickness was seen to increase with longer treatment time and higher RF power levels with behaviour characteristic of a diffusion limited process. Annealing led to a removal of the oxide layer by diffusion of oxygen into the bulk of the samples. This indicates that where the oxide layer is sufficiently thin, it should be possible to produce a surface with low enough oxygen content to have adequate conductivity and high enough surface escape probability to allow photoemission at UV wavelengths. Ar plasma treatment was seen to result in a very thin oxide film which could satisfy these requirements and thus might be preferable. Data from single crystal copper samples showed similar total oxygen content for all the surfaces analysed.

An Innovative Lens Type FinLine to Microstrip Transition

Due to the disadvantages of vacuum tubes in terms of warm-up time, size, and high-voltage needs, solid-state power amplifiers (SSPAs) with gallium nitride (GaN) monolithic microwave integrated circuits (MMICs) are the key solution for power levels up to some kilowatts in continuous wave. An SSPA is the most convenient solution for these RF power levels due to its low weight, small size, negligible warm-up time, low-voltage operation, and high reliability. Spatial power amplifiers (SPAs) combining techniques are the best candidates for SSPAs due to the intrinsic low attenuation in dividing and combining functions. SPAs mainly use two types of probes: transverse and longitudinal, such as FinLines. This paper describes a broadband FinLine to microstrip (FLuS) transition based on dielectric lens theory. Comparative simulations with traditional FinLine transitions show a significant improvement in matching performances and a very significant increase in mechanical resistance of the transition. The proposed innovative FLuS uses a substrate shaping designed according to dielectric lens theory. Frequency simulations of a FLuS inside the WR22 waveguide are shown. These evidence the better performances of this transition than the classic FLuS transition using quarter-wave transformer (QWT) matching. A Q band spatial power combiner with dielectric lens FLuS was made and measured, showing the excellent performances of this innovative FLuS transition.

Synthesis of Ag-decorated vertical graphene nanosheets and their electrocatalytic efficiencies

Herein we report the successful preparation of silver (Ag)-decorated vertically oriented graphene sheets (Ag/VGs) via helicon wave plasma chemical vapor deposition (HWP-CVD) and radiofrequency plasma magnetron sputtering (RF-PMS). VGs were synthesized in a mixture of argon and methane (Ar/CH4) by HWP-CVD and then the Ag nanoparticles on the prepared VGs were modified using the RF-PMS system for different sputtering times and RF power levels. The morphology and structure of the Ag nanoparticles were characterized by scanning electron microscopy and the results revealed that Ag nanoparticles were evenly dispersed on the mesoporous wall of the VGs. X-ray diffraction results showed that the diameter of the Ag particles increased with the increase in Ag loading, and the average size was between 10.49 nm and 25.9 nm, consistent with the transmission electron microscopy results. Ag/VGs were investigated as effective electrocatalysts for use in an alkaline aqueous system. Due to the uniquely ordered and interconnected wall structure of VGs, the area of active sites increased with the Ag loading, giving the Ag/VGs a good performance in the oxygen evolution reaction. The double-layer capacitance (C dl) of the Ag/VGs under different Ag loadings were studied, and the results showed that the highest Ag content gave the best C dl (1.04 mF cm−2). Our results show that Ag/VGs are likely to be credible electrocatalytic materials.

A 900 MHz, Wide-Input Range, High-Efficiency, Differential CMOS Rectifier for Ambient Wireless Powering.

This paper presents a wide dynamic-range CMOS rectifier with high efficiency and high sensitivity for RF energy harvesting. A new adaptive-biasing scheme is implemented using stacking diodes with dynamic threshold voltage to mitigate the reverse-leakage current of the NMOS rectifying devices at high RF power levels. The proposed design employs the adaptive-biasing technique to control the conduction of the PMOS rectifying devices with self-bulk biasing of the feedback diodes to minimize the leakage current. The proposed novel techniques extend the dynamic range of the RF-to-DC power converter with high efficiency, which is 17 times better than a conventional cross-coupled rectifier. The prototype is implemented using a standard 65 nm CMOS technology and occupies a 0.0093 mm2 active area. The proposed design achieves a peak power conversion efficiency (peak PCE) of 73%, −18.8 dBm 1-V sensitivity, and a superb dynamic range of 17.3 dB with efficiency greater than 80% of its peak PCE, which outperforms the state-of-the-art RF CMOS rectifiers, when operating at UHF 900 MHz with a 100-KΩ load.

A LUT-based scheme for LNA linearization in direct RF sampling receivers

Direct RF sampling receiver – a fully digital receiver architecture – undoubtedly becomes a favored choice for HF/VHF as this approach inherently bypasses the legacy nonlinearities caused by analog components. In DRF-RF and wideband multichannel in general, LNA is still an indispensable component to ensure the receiver’s sensitivity. However, with the presence of multiple channels, the total RF power often surpasses the linear threshold that LNA and the amplified signal become severely distorted. This paper proposed a method for mitigating the LNA distortion using the look-up table (LUT) approach. Specifically, our receiver is designed with two modes of operation. In training mode, a built-in signal circuit generates a training signal for extracting the LNA characteristic and eventually reconstructs the inverse LNA nonlinear model in the form of a LUT memory. During the receiving mode, a linearization circuit reverses the distortion impact by matching the RF power level with the inverse nonlinear model pre-stored in the LUT. The effectiveness of the proposed distortion compensation method first is evaluated by a MATLAB simulation with a multi-channel DRF-RF model. The simulation results show that the proposed approach significantly improved the SNDR for the channel of interest. Furthermore, the model has been practically verified, where the actual distorted signals are sampled from a commercial LNA (ZFL-500LN+) by a customized FPGA board. Results from measurements show an improvement of ∼7 dB for SNDR and 27% for EVM in a strong distortion scenario of QPSK modulation signal.

Passive High Power RF Comb Filters Using Epitaxial GaN/NbN/SiC HBARs.

This report presents the first demonstration of passive RF comb filters made using epitaxial GaN/NbN/SiC high overtone bulk acoustic resonators (epi-HBARs). The two-port device is fabricated on electronic-grade GaN, electrically transduced, and acoustically coupled. The multi-mode epi-HBAR comb filter demonstrated here has 158 sharp filter passbands periodically distributed between 1 and 4 GHz (L-S-bands) with a free spectral range (FSR) of 17 MHz. The individual passbands of the epi-HBAR comb filter demonstrate transmission bandwidths (BWs) up to 800 kHz, f × Q values of up to 7×1014 Hz, and an average [Formula: see text] figure of merit of 41.2 at room temperature. The GaN/NbN/SiC epi-HBAR comb filter is capable of operating at high RF power levels, with linear and distortion-free performance seen up to at least 1 W of continuous wave (CW) power and up to at least 10 W of pulsed power. The compact epi-HBAR comb filters can be co-fabricated with GaN-based electronics and could potentially replace larger, off-chip or discrete-component comb filters. They can be used for spectrum sensing and as signal processing elements for remote sensing and pulsed radar.

A Reconfigurable RF-to-DC Converter using an Adaptive Control Loop for a Passive Wake-up Receiver

In this paper, a new reconfigurable RF-DC converter structure with an adaptive control loop is proposed for the efficient implementation of passive-type wake-up receivers, which are essential for wireless sensor networks using IoT devices. The proposed reconfigurable RF-to-DC rectifier structure automatically determines the number of rectifier units used for power conversion based on the output DC voltage obtained from the input RF power signal. Thus, high power-conversion efficiency is always maintained regardless of the input RF power level. In addition, a 4-bit switched capacitor bank is used to adjust the impedance matching network required for RF rectifiers. It is automatically configured by the proposed adaptive control loop according to the input RF power. The rectifier was implemented using a 0.25-μm CMOS process. The DC output voltage was obtained with a 100-kΩ load resistor and 915-MHz RF input frequency. When this output voltage is more than 0.5 V, the performance of the converter has a very wide power range of RF input of more than 25 dB (from -22 dBm to 5 dBm). It also has a power conversion efficiency above 30%.

Power Measurement of Radio Frequency Signals Based on Subsampling and Negative Loop Feedback

A component or system's output signal level is often the critical factor in the design and ultimately the purchase and performance of almost all RF and microwave equipment. Because signal power level is so important to the overall system performance, it is critical when specifying the component that builds up the system. Most of power sensors convert high frequency power to a DC or low frequency signal that the power meter can then measure and relate it to a certain RF power level. The three main types of sensors for sensing power are thermistor, thermocouple and diode detector. In this paper, we explain a new method used for power measurement in the frequency range of 10MHz to 1GHz. In this method, a D-type flip-flop was used to convert the main signal to a low frequency signal.

Thermal analysis for fundamental power coupler of HALF 499.8 MHz superconducting cavity

The preliminary research work of Hefei Advanced Light Facility (HALF), a fourth generation diffraction limit storage ring, is in progress. Two 499.8 MHz superconducting cavities may be used in the HALF RF system. RF power will be feed into each cavity through a coaxial fundamental power coupler (FPC). Thermal design of the coupler is very important because of the large power losses on the coupler will cause overheating. Accurate and fast thermal analysis is a challenge in the thermal design. In this paper, two thermal analysis methods for evaluating the cooling effect of the coupler were compared. Computational Fluid Dynamics (CFD) code is used to perform thermal-fluid coupled analysis for the coupler in the first method, which is quite accurate but time-consuming. In the second method, average convective heat transfer coefficient calculated by correlation equations based on experimental results is used to evaluate the heat transfer between the fluid and the cooling pipe wall. The calculation time of the first method is about four times that of the second method. The simulation results of the two methods are consistent well at high flow rate, especially for turbulent flow. Therefore, the second method was used to perform thermal simulation under different cooling conditions and RF power levels. The influence of thermal radiation on the heat load to the cryogenic environment was also given in this paper. Simulation results show that thermal radiation has a slight impact on the heat load. When the copper emissivity equal to 0.02, the total static and dynamic heat load to 4.5 K are 0.833 W and 2.614 W at the power level of 200 kW, and the heat load to 4.5 K cryogenic environment caused by thermal radiation is 0.065 W.