Radio Frequency Power Levels Research Articles

Investigating the influence of RF power on the surface morphological and optical properties of sputtered TiO2 thin films

Thin films of titanium dioxide (TiO2), with thicknesses ranging from 105 to 231 nm, were deposited on glass substrates using radio-frequency (RF) magnetron sputtering in an argon atmosphere at four distinct RF power levels: 40, 70, 100, and 130 W, with the deposition time kept constant. The crystalline structure, surface morphology and optical and semiconductor properties of the obtained films were analyzed using X-ray diffraction (XRD), Atomic Force Microscopy (AFM) and UV–visible transmittance spectroscopy. These analyses revealed that the crystallinity of the films improves with increasing RF power, corresponding to an increase in film thickness. Consequently, the samples transition from poorly crystalline or amorphous structure to a monocrystalline rutile phase with a (110) texture. However, at the highest RF power studied, this texture is partially disrupted by the formation of nanocrystals with different orientations. The surface roughness exhibited multifractal characteristics, with complexity systematically decreasing and surface stiffness reducing as RF power increased. Refractive indices and optical band gap energies were determined using the Swanepoel and Tauc plot methods, respectively. The films exhibited a notable increase in the refractive index and a decrease in the optical band gap, from 3.81 eV to 3.52 eV, as the RF power was increased. This underscores the influence of RF power on the optical and semiconductor properties of TiO2 films.

Thyroid Radiofrequency Ablation-Thermal Effects on Recurrent Laryngeal Nerve Using Continuous Intraoperative Neuromonitoring Animal Model.

When performing radiofrequency ablation for thyroid nodules, it is essential to avoid thermal injury to the recurrent laryngeal nerve. This porcine animal model study used continuous intraoperative neuromonitoring to investigate the thermal safety parameters of thyroid radiofrequency ablation. Porcine animal study. University animal laboratory. Twelve piglets were tested at different radiofrequency power levels, and the real-time electromyography signal changes were recorded under continuous intraoperative neuromonitoring. The spread heat study (8 piglets) included spontaneous recovery tests and cold water irrigation tests to investigate the safety distance from the recurrent laryngeal nerve to the active tip during 5-second activation with standard stimulation patterns. The residual heat study (4 piglets) investigated the safety cooling durations by touching the recurrent laryngeal nerve with the tip after a 5-second activation. In the spread heat study, substantial signal attenuation events were observed at an spread heat distance of 2, 3, 5, and 5 mm when the power was set as 10, 20, 30, and 50 W, respectively. No signal recovery could be observed in 20 minutes with or without cold water irrigation in the injured recurrent laryngeal nerve area. The residual heat study shows the residual thermal effect of the tip is minimal, and no substantial signal attenuation event was observed at all experiments. This innovative study established the thermal safety parameters for radiofrequency ablation in a porcine model at various power levels, which can potentially assist operators in delineating a precise ablation field and providing effective thyroid ablation treatment safely.

Design and Implementation of a Photonic-Based Electronic Warfare System

Nowadays, the Radio frequency (RF) Photonics become an inevitable candidate to address several military related potential applications including electronic warfare (EW), photonic signal processing (PSP), photonic-based RF transportation, and photonic communications. As part of this emerging technology development/requirement, we designed a photonic-based EW systems (PEWS) in the optisystem environment (later implemented using optoelectronic components) to extract various radar waveforms such as continuous wave (CW), pulsed wave, and frequency/phase modulated wave. All these radar waveforms are transmitted and captured by the proposed/implemented PEW system, and then processed to construct the radar signatures from its electromagnetic (EM) spectrum/signals. The key parameters of various waveforms generated and processed in our research work are varied, over the time, during the performance validation tests. The values of key parameters of the waveforms: RF CW signal frequencies, pulse repetition times (PRTs), pulse-widths, Barker code phase modulations, Frank code poly-phase modulations, sweep frequencies, and RF power levels; are 100 Hz through 8 GHz, 10 ms through 2 µs, 750 ns through 2 ns, 0o /80o, 0o /90o /180o /270o, and -84 dBm through 30 dBm, respectively. The details of PEWS design approaches, their implementation methodologies, and different performance validation experimental results are reported, and analyzed. The limitations, and possible immediate research contributions/requirements are also listed.

Enhancement of the thermoelectric performance of (BiSb)2Te3 films by single target sputtering

In this study, (BiSb)2Te3 thin films were deposited onto glass substrates at a temperature of 300 °C, utilizing radio frequency (RF) sputtering across a range of growth conditions. The primary focus of this investigation was to analyzse the effects of varying RF power, chamber gas pressure, and annealing temperature on the thermoelectric properties of the films, deposited by an exclusively-made single target.Notably, it was observed that increasing the annealing temperature significantly boosted both the deposition rate and grain size. Through carefully optimizsing growth conditions and subsequent annealing procedures, it was discerned that thin films cultivated at higher RF power levels exhibited markedly improved electrical conductivity, attributed to a discernible rise in carrier concentration. Furthermore, films generated under the RF power of 37.5 W showed a noteworthy augmentation in the Seebeck coefficient, recording approximately 147 μV/K. This enhancement in Seebeck coefficient correlated with the attainment of the highest power factor, reaching an impressive 220.57 μW/mK2.

Zero-Field ODMR and relaxation of Si-vacancy centers in 6H-SiC

Silicon vacancies in silicon carbide (SiC) have been proposed as interesting candidates for quantum technology applications such as quantum sensing and quantum repeaters. SiC exists in many polytypes with different plane stacking sequences, and in each polytype, the vacancies can occupy a variety of different lattice sites. In this work, we focus on the three important charged silicon vacancies in the 6H-SiC polytype. We record the photoluminescence and continuous-wave optically detected magnetic resonance (ODMR) spectra at different radio-frequency power levels and different temperatures. We individually select the zero-phonon lines of the different silicon vacancies at low temperatures and record the corresponding ODMR spectra. ODMR allows us to correlate optical and magnetic resonance spectra and thereby separate signals from V 1 and V 3. The results also explain the observed sign change of the ODMR signal as a function of temperature.

Phase nonlinearity reduction of a complex receiver having multiple phase correlators

AbstractThis article analyzes and describes phase nonlinearity reduction techniques in detail for ultra wideband complex receivers to qualify airborne system requirements. Phase nonlinearity directly affects the final frequency resolution coming from unknown threats. Thereby, the reduction of phase nonlinearity of all radio frequency (RF) channels including phase correlators is very essential. A simple phase nonlinearity calculation step has been shown in this article without taking the help of any coding (software). A detail excel sheet–based phase nonlinearity calculation has been explained and estimated with examples. Power and phase corrections are especially done to keep the RF response flat over a wide frequency spectrum to enhance better phase linearity. This is done by designing various equalizers with different slope gradients and adjusting power levels by using attenuation pads or reducing feeds by other means. Phase nonlinearity has been kept under control by tracking the phase of mixers, other passive/active components within ±5°, and all the RF channels within ±15°. The power level has been adjusted within P1dB or just beyond the P1dB to keep the harmonic level less, which in turn controls phase nonlinearity in all the active devices. The performance of phase correlators against various power levels has been analyzed to finalize uniform RF and LO power levels (feed) at the input of the phase correlators. The level of uniform feed has been decided after reviewing phase nonlinearity responses of the correlators. Thus, the final resolved frequency become accurate (<3 MHz root mean square). Finally, four receivers have successfully been developed and evaluated over temperature (−40°C to +71°C) and vibration to establish the method for mass production.

Wideband Power-Dependent Power Limiter Based on Distributed Low-Temperature Superconductor rf-SQUIDs for Cryogenic RF Receivers

A novel design of a radio-frequency (RF) power limiter for protecting sensitive superconductor receiver components from high-power microwave signals is presented. In this approach, two low- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${T} _{c}$ </tex-math></inline-formula> superconductor microstrip lines, one of which is coupled with an array of RF superconducting quantum interference devices (rf-SQUIDs), are combined with a pair of hybrid couplers to provide the power limiting operation at very low RF power levels. The key concept is built on the fact that a microstrip line coupled to an array of rf-SQUIDs behaves as a power-dependent phase shifter and its phase can be controlled by the input RF power. This phenomenon is exploited to achieve the desired RF power-limiting operation. The device is fabricated using an eight-layer niobium-based superconducting process node SFQ5ee by MIT Lincoln Laboratory (MIT-LL). A monolithically integrated wideband hybrid coupler is used in this design as it dictates the bandwidth of the overall device. The operating frequency of the power limiter is 10 GHz with a 2-GHz bandwidth. The performance of the device is measured for input RF power levels ranging from −30 to +10 dBm, as well as arising intermodulation products are experimentally investigated. The output power increases linearly with the input power up to −15 dBm, and for higher power levels, the device offers an increasing attenuation to limit the output RF power starting above −15 dBm.

A wideband hybrid combiner design for ITER ion cyclotron radio frequency source.

The high-power radio frequency source for ion cyclotron heating and current drive of ITER tokamak consists of two identical 1.5MW amplifier chains. These two chains will be combined using a wideband hybrid combiner with adequate coupling flatness, phase balance, return loss, and isolation response to generate 2.5MW radio frequency (RF) power in the frequency range of 36 to 60MHz. As part of the in-house development program at ITER-India, a wideband hybrid combiner with coupling flatness and return loss/isolation better than 0.4 and -25 dB, respectively, has been simulated. A detailed analysis for matched load performance of the hybrid combiner for the output power level of 3MW as well as mismatched load performance for load power of 2.5MW with voltage standing wave ratio 2.0 and 3.0MW with voltage standing wave ratio 1.5 has been performed. Based on the simulation, a prototype model was in-house fabricated, and the simulated results have been validated experimentally in splitter and combiner mode. To evaluate performance as a combiner, two solid-state power amplifiers were combined through the prototype combiner for input power levels up to 2.5 kW on matched and mismatched load conditions. In the power splitter experiment, the RF power level up to 1.5MW from a single amplifier chain was split through the prototype combiner to be dumped in the high power loads in the frequency range of 36 to 60MHz.

Hybrid Power Harvesting From Ambient Radiofrequency and Solar Energy

In this letter, a power harvester with a Schottky diode and a photodiode has been designed to harvest ambient radiofrequency (RF) and solar power in a cooperative way. The RF power is collected by a coplanar waveguide-fed circularly polarized antenna operating in wifi band and converted into the dc one by a rectifying circuit composed of the Schottky diode, and meanwhile the solar energy is harvested by the photodiode to bias the Schottky diode in the rectifying circuit. With the RF and solar power simultaneously injecting into the rectifying circuit, the resulting power conversion efficiency is greatly increased for the same RF and solar power levels in a range from −20 to 0 dBm. The prototype of the proposed harvester is fabricated, and the measured results demonstrate a maximal total PCE of 73% and a maximal output power of 1450 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> W.

Performance analysis of multi hole directional coupler for different hole profiles

The most critical and efficient circuits in guide wave single-mode systems are directional couplers. For Radio Frequency (RF) system designers, the directional coupler is a useful measurement unit. It offers not only an amplitude measured image of RF power levels but also identifies forward and reflected signal components to better characterize loads. They have been used in various telecommunications instruments, such as splitters, wavelength-dividing multiplexers, optical switches, etc. The paper streamlines the designing process of the waveguide coupler and its performance thereafter. The effects of hole shape and count for waveguide directional couplers are further investigated and compared in this study. The directional coupler with elliptical-shaped holes has been found to be more effective than its circular-holed counterpart. Also, compared to a coupler with circular holes, an elliptical hole directional coupler looks to be able to achieve high coupling with a reduced number of holes.

A Study on the Characteristics of Inductively Coupled Plasma Nitridation Process

In this study, we investigated the nitridation of silicon oxide film surfaces using an inductively coupled plasma source. The plasma parameters and nitride film characteristics were measured under various nitrogen gas pressures and radio frequency power levels. Plasma parameters such as electron density, electron temperature, and ion density were measured and analyzed using several instruments. The nitridation characteristics of the thin films were characterized using X-ray photoelectron spectroscopy. The findings provide information on the correlation between nitridation rate and process parameters.

Quad-Band Rectenna for Ambient Radio Frequency (RF) Energy Harvesting.

RF power is broadly available in both urban and semi-urban areas and thus exhibits as a promising candidate for ambient energy scavenging sources. In this research, a high-efficiency quad-band rectenna is designed for ambient RF wireless energy scavenging over the frequency range from 0.8 to 2.5 GHz. Firstly, the detailed characteristics (i.e., available frequency bands and associated power density levels) of the ambient RF power are studied and analyzed. The data (i.e., RF survey results) are then applied to aid the design of a new quad-band RF harvester. A newly designed impedance matching network (IMN) with an additional L-network in a third-branch of dual-port rectifier circuit is familiarized to increase the performance and RF-to-DC conversion efficiency of the harvester with comparatively very low input RF power density levels. A dual-polarized multi-frequency bow-tie antenna is designed, which has a wide bandwidth (BW) and is miniature in size. The dual cross planer structure internal triangular shape and co-axial feeding are used to decrease the size and enhance the antenna performance. Consequently, the suggested RF harvester is designed to cover all available frequency bands, including part of most mobile phone and wireless local area network (WLAN) bands in Malaysia, while the optimum resistance value for maximum dc rectification efficiency (up to 48%) is from 1 to 10 kΩ. The measurement result in the ambient environment (i.e., both indoor and outdoor) depicts that the new harvester is able to harvest dc voltage of 124.3 and 191.0 mV, respectively, which can be used for low power sensors and wireless applications.

Influences of Oxygen Plasma Posttreatment on Electrical Characteristics of Amorphous Indium–Gallium–Zinc–Oxide Thin‐Film Transistors

A thin‐film transistor (TFT) using amorphous indium–gallium–zinc oxide (a‐IGZO) as an active layer is annealed at 300 °C after deposition and then treated with oxygen plasma. To analyze the effect of radio frequency (RF) power of the plasma generator on the a‐IGZO TFT, as‐deposited and plasma‐treated devices using RF power levels of 60, 120, and 180 W are fabricated and characterized. It is demonstrated that the RF power setting of the plasma generator influences the threshold voltage (V th), electron mobility, on/off current ratio and subthreshold swing of the devices alongside the transmittance and absorption coefficient of the a‐IGZO layer. The a‐IGZO TFT with oxygen plasma treatment at 60 W shows the best performance with a V th of 0.4 V, electron mobility of 14.8 cm2 V−1 s−1, an on/off current ratio of 4.8 × 108, and a subthreshold swing of 0.6 V dec−1. In addition, compared to the as‐deposited device, the bandgap widens from 3.65 to 3.72 eV, and the absorption coefficient of the 2.0–3.7 eV energy range decreases, which is due to the decreased density of tail states, and that improves electron mobility. When the RF power applied in the oxygen plasma treatment is increased to 120 and 180 W, the optical, electrical, and surface characteristics deteriorate.

Radio frequency mixing modules for superconducting qubit room temperature control systems.

As the number of qubits in nascent quantum processing units increases, the connectorized RF (radio frequency) analog circuits used in first generation experiments become exceedingly complex. The physical size, cost, and electrical failure rate all become limiting factors in the extensibility of control systems. We have developed a series of compact RF mixing boards to address this challenge by integrating I/Q quadrature mixing, intermediate frequency/LO (local oscillator)/RF power level adjustments, and direct current bias fine tuning on a 40 × 80mm2 four-layer printed circuit board with electromagnetic interference shielding. The RF mixing module is designed to work with RF and LO frequencies between 2.5 and 8.5GHz. The typical image rejection and adjacent channel isolation are measured to be ∼27 dBc and ∼50 dB. By scanning the drive phase in a loopback test, the module short-term amplitude and phase linearity are typically measured to be 5 ×10-4 (Vpp/Vmean) and 1 ×10-3 radian (pk-pk). The operation of the RF mixing board was validated by integrating it into the room temperature control system of a superconducting quantum processor and executing randomized benchmarking characterization of single and two qubit gates. We measured a single-qubit process infidelity of 9.3(3) × 10-4 and a two-qubit process infidelity of 2.7(1) × 10-2.

Apparent thermal death kinetics of adult red flour beetle (Tribolium castaneum) in stored canola (Brassica napus L.) seeds using a pilot-scale 50-Ω radio frequency (RF) heating system

Adult Tribolium castaneum infesting canola seeds at 9% moisture content were treated using a 50-Ω radio frequency heating system and the thermal mortalities of the insects were determined. The infested seeds were treated at temperatures of 24–65 °C with radiofrequency (RF) heating power at 3 kW, 5 kW, and 7 kW. More than 80% of the insects were killed at 65 °C at all the three power levels. The survival rate of the adult T. castaneum decreased with temperature and RF power level. The effect of selective heating on mortality of insects increased at the higher RF powers. An inverse simulation was used to estimate the kinetic parameters of thermal death in adult T. castaneum. The thermal kinetic models developed in this study were solved using the 4th order Runge-Kutta method on a MATLAB platform. The thermal death kinetics for adult T. castaneum followed the 1st order reaction with Ea of 97.50 kJ/mol and k0 of 6.5 × 1013. The lethal time (LTs) calculated using the thermal death kinetic model developed in the study agreed well with the LTs determined experimentally.

Physical principles of radio-frequency magnetron sputter deposition of calcium-phosphate-based coating with tailored properties

The influence of radio-frequency (RF) magnetron sputter deposition conditions (RF power discharge density, working gas atmosphere, deposition time, and electrical substrate bias) on the properties (microstructure, texture, Ca/P ratio) of nanocomposite calcium-phosphate (CaP) coatings has been reported. A phenomenological model was developed to explain the formation of the RF magnetron sputter-deposited hydroxyapatite (HA) coating depending on the various deposition conditions. In the initial deposition stages, a nanocrystalline or quasi-amorphous CaP layer is formed. As both the film thickness and temperature gradient across the film thickness increased, the crystallisation of the HA phase occurred, which led to the formation of the fibre 〈002〉 texture in the films. The increase in the coating thickness also resulted in an increase in the grain size and a decrease in the residual microstress. The cross-section of the coating revealed a polycrystalline fibre structure with wedge-shaped columns. The addition of water vapour to an Ar atmosphere allowed to restore the hydroxyl groups in the composition of the HA coatings. The topography of the СaP coating surface that had irregular grains with different form and shape grown out of the coating plane was established, which extended the well-known structural zone models (Thornton, Monsieur, Movchan and Demchishin, Anders, etc.) and was formed both at a relatively low substrate temperature of 160–200 °С and RF power level when the substrate was bombarded with positive ions with an energy of ~100 eV, regardless of the working gas atmosphere used (argon or oxygen), resulting in a the growth of a coating with a preferably amorphous or nanocrystalline structure.

A Self-Gating RF Energy Harvester for Wireless Power Transfer With High-PAPR Incident Waveform

In this article, we propose a self-gating radio frequency (RF) energy harvester (RFEH) for reaching a high-power harvesting efficiency (PHE) at a low incident RF power level with a high peak-to-average power ratio (high-PAPR) waveform. It includes a power switch between a cross-coupled rectifier and its supplied load to cut off the reverse leakage current in between the short power bursts. The power switch is dynamically controlled based on an indication of the ability of the RFEH to effectively charge the load at the instantaneous incident power level. This is achieved by comparing the load voltage with the open-circuit voltage of a replica rectifier. A comparator with optional proteresis (reversed hysteresis) is proposed for compensating its logic delay at the start and at the end of the short RF power bursts. As a result, the power switch is accurately turned on only during the power bursts. The self-gating RFEH was prototyped for 2.45-GHz wireless power transfer (WPT). It includes a cross-coupled rectifier with the proposed self-gating circuit fabricated in a 65-nm process, a discrete balun, a parasitic-aware-sized π matching network, and an off-the-shelf power management unit (PMU) with maximum power point tracking (MPPT). Measurement results show sensitivity as low as -26.7 dBm with a peak PHE of 32.3% at -14.1-dBm incident power. Compared with the state-of-the-art works, the proposed design significantly improves the RFEH performance at the target low average incident power.

Batteryless and Self-Reconfigurable Multimode RF Network using All-Passive Energy Smart-Sensing

In recent years, replacing the external control stimuli with internal control using characteristics of radio frequency (RF) signals (such as waveform or power level) has attracted considerable attention to the design of reconfigurable multifunctional RF devices. However, even with the most exciting techniques, the control process always needs a chip-based system to sense the power level or waveform of the incident RF signal, which is realised by additional supporting electronic components of the sensing and microcontroller circuits. Therefore, to achieve a batteryless structure, a majority of conventional works focus on using energy harvesters to convert energy from external environmental sources to DC energy for the electronic circuits. Herein, we propose a novel alternative approach to replace the traditional energy harvesters in batteryless RF devices with all-passive energy smart-sensing circuits. By exploiting the features of a nonlinear semiconductor device under different incident RF power values, the proposed network can passively self-sense the RF power level and dynamically self-control RF signal flow and power ratio. The operation of the proposed network can be considered as purely self-adaptation with control from the RF power level. Moreover, normal RF devices can be transformed to all-passive and batteryless purely self-reconfigurable devices via integration with the proposed structure. As proof of concept, the proposed network is integrated with a two-port antenna to experimentally demonstrate its purely self-reconfigurable polarisation. The proposed strategy is hereby expected to extend the field of batteryless self-reconfigurable multifunctional RF devices and pave promising new paths for the development of future intelligent, smart RF devices.

Effect of Radio Frequency Low Pressure Cold Plasma on Total Phenol, Antioxidant Activity and Colour Degradation Kinetics of Red Chilli Pepper Powder

The study was aimed to analyse the effect of low pressure cold plasma treatment [operated at 60.8 kPa on the quality parameters of red chilli pepper powder (RCPP)]. The experiments were conducted at two radio frequency power levels (60 W, 120 W) over a time range from 0 to 10 min. Total phenols, antioxidant activity, colour, and moisture content were determined. Results showed that radio frequency operating power and treatment time had significant negative effects (p &lt; 0.05) on the quality parameters analysed. Cold plasma treatment reduced the redness, total phenol content, moisture content, and increased the antioxidant activity of the RCPP. Changes in the quality of the treated samples, especially the colour degradation were significant after 4 min of treatment. Degradation kinetics was determined for parameters studied to ascertain their order of reaction during cold plasma treatment. The order of reaction was decided from best fit models with the highest R2, minimum bias, and error sum of squares. Total phenol followed a zero-order, whereas antioxidant activity and colour followed first-order reactions. The study explored the possibilities and impact of using cold plasma for powdered food materials.

Effects of geometry and orientation of food products on heating uniformity during radio frequency heating

In radio frequency (RF) assisted heat treatment of food products, heating behavior depends on the composition and geometry of a product. In this study, the effect of salt added to a food simulant on its dielectric properties and penetration depth (dp) were determined across a temperature range from 5 to 80 °C. Three primitive geometries (cube, cylinder and sphere) of a food simulant having a standardised volume (3.98 × 10−4 m3) heated in a custom-built 50 Ω RF system to investigate the impact of sample geometry and orientation on power absorption and heating uniformity. Experimental results revealed vertical oriented cylinder samples followed by cubes showed better temperature uniformity. The temperature at the core of food simulant samples after 6 min RF heating using 500 W power was 44 ± 7.1 °C, 45.3 ± 0.9 °C and 52.9 ± 3.5 °C in cube, cylinder, and sphere sample, respectively. However, the sphere sample was characterized by having the hottest spot at the bottom section. RF power level also played a significant role in heating uniformity with lower power input resulting not only in a slower heating rate but also in less uniform temperature distribution. This study provided a potential insight on the use of food simulants for evaluating RF heating design and performances.