Radio Frequency Coupling Research Articles

Summary of Wireless Charging Technology for Electric Vehicles

The rapid popularity of electric vehicles has promoted the rapid development of wireless charging technology. This paper reviews the current research progress and application status of wireless charging technology for electric vehicles. Inductive coupling, magnetic resonance coupling and non-directional radiofrequency radiation, three main wireless power transmission methods, including their principles and advantages, are introduced. In addition, the practical application of the technique, such as near field application and far field application, is also discussed. Finally, the development direction of wireless charging technology for electric vehicles in the future is looked forward, including the key technical paths of optimizing system design, improving energy transmission efficiency and reducing system cost. In summary, this paper aims to provide comprehensive theoretical support and practical guidance for the research and practice of wireless charging technology for electric vehicles.

The preliminary study of etching characteristics of atmospheric pressure trifluoromethane plasma jet etching

Abstract The capacitive coupling radio frequency atmospheric pressure plasma jet for silicon etching, through the carrier gas carrying trifluoromethane gas, varying the gas flow rate for plasma etching. It finds the impact of varying gas flow rates on plasma etching and analyzes the resulting two-dimensional and three-dimensional surface topographies using surface profilometer. Experimental findings indicate that at a trifluoromethane flow rate of 250 sccm and a working distance of 6 mm, the etching rate achieves 38.7 μm/min. Notably, the research emphasizes the crucial role of trifluoromethane (CHF3) gas in plasma etching, highlighting its fluorocarbon ratio and chemical structure as primary factors influencing the etching process on monocrystalline silicon. Ultimately, the study proposes a methodology involving trifluoromethane gas for silicon wafer etching, enabling the transformation of micro-patterns onto crystalline silicon using a mask. This research contributes valuable insights into optimizing plasma etching techniques for microfabrication processes in semiconductor technology.

A wireless, battery-free microneedle patch with light-cured swellable hydrogel for minimally-invasive glucose detection

The escalating global prevalence of diabetes necessitates the development of advanced diagnostic methodologies that are both minimally invasive and devoid of discomfort. This study introduces a wireless battery-free passive microneedle patch with CMC-pHEA GelMA-GOx (CMC: sodium carboxymethyl cellulose; pHEA: polyethylene glycol diacrylate, 2-hydroxyethyl acrylate; GelMA: gelatin methacryloyl; GOx: glucose oxidase) light-cured swellable hydrogel for minimally-invasive glucose detection. The core of this technology combines microneedle with Radio-Frequency (RF) coupling detection, achieving extraction capacity; the microneedle lies in the use of composite hydrogel composed of a freeze-dried CMC-pHEA nanogel and GelMA-GOx, specifically fabricated to be selectively glucose-responsive through cross-linking with glucose oxidase. Upon exposure to interstitial fluid, the hydrogel microneedles swell in proportion to the glucose concentration, enabling glucose binding and facilitating the detection process. A flexible antenna, which is integral to the microneedle substrate as a passive sensing component, detects changes in the swelling of the hydrogel; these are reflected in the RF parameters (frequency, magnitude) variations, which are directly correlated with glucose levels. Furthermore, the results are near field wirelessly detected through a readout coil, simplifying sensing patch configurations. This method not only integrates the glucose monitoring process by combining extraction and detection into a single step but also enhances patient comfort. The platform’s sensitivity, specificity, and minimal invasiveness make it a promising tool for diabetes management and continuous glucose monitoring. By demonstrating the successful application of RF technology in wireless sensing applications, this study paves the way for advanced, user-friendly glucose monitoring solutions.

Coupled stack-up volume RF coils for low-field open MR imaging.

Low-field open magnetic resonance imaging (MRI) systems, typically operating at magnetic field strengths below 1 Tesla, has greatly expanded the accessibility of MRI technology to meet a wide range of patient needs. However, the inherent challenges of low-field MRI, such as limited signal-to-noise ratios and limited availability of dedicated radiofrequency (RF) coils, have prompted the need for innovative coil designs that can improve imaging quality and diagnostic capabilities. In response to these challenges, we introduce the coupled stack-up volume coil, a novel RF coil design that addresses the shortcomings of conventional birdcage in the context of low-field open MRI. The proposed coupled stack-up volume coil design utilizes a unique architecture that optimizes both transmit/receive efficiency and RF field homogeneity and offers the advantage of a simple design and construction, making it a practical and feasible solution for low-field MRI applications. This paper presents a comprehensive exploration of the theoretical framework, design considerations, and experimental validation of this innovative coil design. We demonstrate the superior performance of the coupled stack-up volume coil in achieving 47.7% higher transmit/receive efficiency and 68% more uniform magnetic field distribution compared to traditional birdcage coils in electromagnetic simulations. Bench tests results show that the B1 field efficiency of coupled stack-up volume coil is 57.3% higher compared with that of conventional birdcage coil. The proposed coupled stack-up volume coil outperforms the conventional birdcage coil in terms of B1 efficiency, imaging coverage, and low-frequency operation capability. This design provides a robust and simple solution to low-field MR RF coil design.

Development and Evaluation of Ferrite Core Inductively Coupled Plasma Radio Frequency Ion Source for High-Current Ion Implanters in Semiconductor Applications.

This study presents the development of a ferrite core inductively coupled plasma (ICP) radio frequency (RF) ion source designed to improve the lifetime of ion sources in commercial ion implanters. Unlike existing DC methods, this novel approach aims to enhance the performance and lifetime of the ion source. We constructed a high-vacuum evaluation chamber to thoroughly examine RF ion source characteristics using a Langmuir probe. Comparative experiments assessed the extraction current of two upgraded ferrite core RF ion sources in a commercial ion implanter setting. Additionally, we tested the plasma lifetime of the ICP source and took temperature measurements of various components to verify the operational stability and efficiency of the innovative design. This study confirmed that the ICP RF ion source operated effectively under a high vacuum of 10-5 torr and in a high-voltage environment of 30 kV. We observed that the extraction current increased linearly with RF power. We also confirmed that BF3 gas, which presents challenging conditions, was stably ionized in the ICP RF ion sources.

Engineering design and manufacturing of a radio frequency plasma driver without Faraday shield for NBI application

A radio frequency (RF) driven ion source is favorable for high-power and long-pulse neutral beam injection (NBI) system. To reduce the damage caused by the isotropic heat and particle fluxes from the plasma, the traditional RF plasma driver of the NBI ion source introduces a Faraday shield (FS) for protection. However, the simulations and experiments show that the FS seriously affects the RF coupling and around 50 % of the input power deposits on the FS. The water-cooled discharge tubes with a double-layer ceramic structure have been developed to avoid using the FS structure. It's expected to improve the RF power transfer efficiency and to promote the development of high-power and long-pulse RF ion source. To verify the feasibility of the double-layer ceramic structure, the paper has carried out the fluid-thermal-structural coupling analysis and the fracture mechanical analysis on two proposed types: the alumina ceramic brazing structure and the silicon nitride ceramic bonding structure. The sample tests and the prototype manufacturing have been completed. Preliminary tests of the plasma discharge on the prototype of the alumina ceramic brazing structure have been launched. A plasma discharge of 30 kW and 20 s have been achieved.

A model of radiofrequency and plasma coupling for compact ion sources and design

Inductive coupling of radiofrequency power to plasma is a complicate process, since it depends from the density of plasma itself, because ionization is a chain reaction process, and, at low density a capacitive coupling may mix with inductive coupling (with no Faraday screen). Plasma temperature Te , density ne and vector potential are closely coupled, giving nonlinear and singular systems of Partial Differential equations, which require slow iterative solutions, motivating the consideration of a 2D model, also as rapid design and first approximation tool. Plasma conductivity and heating depend on collision rate, which includes also the so-called stochastic collisions (mainly electron collisions with walls), proportionally more important at low gas density ng . Conductivity is also affected by static and radiofrequency magnetic fields; results for skin depth and stochastic collision estimates are reported. The transport of Te and ne inside source can be controlled by a magnetic filter B f . Considering a 5 cm radius H- ion source as example, solution of ne and Te are reported as a function of filter strength B fa, applied rf power and wall status; solver convergence methods andkey plasma observables are briefly discussed. Due to small dimension, a filter strength B fa in the order of 8 mT is needed to achieve electron temperature lower than 2 eV (for negative ion production) at extraction.

Experimental Investigation on the Effect of “Linear-Rise” Amplitude Modulation on a Pulsed Capacitively Coupled Radio-frequency Argon Discharge

Objective: This work focused on the effect of “linear-rise” amplitude modulated waveform on the time evolution of some typical electrical and plasma parameters in a pulsed radio-frequency capacitively coupled argon discharge. Methods: The pulse-on phase of a square wave pulse is divided into two distinct stages, namely, the “linear rise” phase (T1 phase) and “constant amplitude” phase (T2 phase). The study focused on exploring the impact of varying T1 durations on the temporal evolutions of these parameters. In the experiment, the electron density was measured time-resolved by a hairpin probe. Phase-resolved optical emission spectroscopy was employed to determine the spatial-temporal distribution of the electron impact excitation dynamics. Additionally, we determined the amplitudes and the relative phase of the discharge voltage and current, as well as the power deposition by analyzing the waveforms obtained from a voltage and a current probe. Results: It was found that with the increase of T1, the critical voltage value required for the plasma ignition becomes lower, and the RF power and the light intensity overshoot less significantly. Upon the overshoot, the plasma when the light intensity exhibits the maximum is dominated by the “overshoot” mode. After the pulse is turned off, the electron density under different T1 durations first decreases with the same rate, and then the decay rate is decreased with the increase of T1. This is because for a longer T1, the neutral gas temperature gets lower, leading to a higher density of neutral gas, so the electron diffusion loss is suppressed. Conclusion: Compared to the square pulse modulated radio frequency capacitively coupled plasmas, the “linear rise” amplitude modulation approach introduces external control knobs to modulate the plasma parameters, which benefits practical material processing. This paper is an experimental measurement implemented in an electropositive gas Ar discharge, and is expected to be extended to the plasmas operated in complex electronegative gases in the future.

Comparison of ion cyclotron wall conditioning discharges in hydrogen and helium in JET

This paper explores the plasma parameters of helium and hydrogen Ion Cyclotron Wall Conditioning (ICWC) discharges performed in JET as part of a He/H fuelling changeover experiment. The conducted study shows that plasma with a higher density is formed in helium than in hydrogen. A distinct glow in the ion cyclotron resonance zone is observed throughout the discharge in He. In H-ICWC discharges, a lower radio-frequency coupling efficiency and coupled power was observed than in He-ICWC discharges. While the helium concentration decreased with the number of H-ICWC pulses and the same for hydrogen in He-ICWC, which is the intended result of the plasma wall interaction in the ICWC changeover procedure, the main features of hydrogen as well as the helium IC discharge do not change dramatically.

Sensing System for Mixed Inorganic Salt Solution Based on Improved Double Label Coupling RFID

As a crucial part in sewage, high-salt wastewater contains abundant corrosive components and heavy metal elements, which makes it difficult for invasive monitoring. Therefore, based on coupling Radio Frequency Identification(RFID) tags, this paper proposes a non-invasive monitoring method for concentration of inorganic salt in sewage. In this method, Cole-Cole model and Slit Cylindrical Capacitance(SCC) model are combined to explore the relationship between capacitance of RFID and concentration of inorganic salt in sewage pipeline. A New Efficient Levenberg-Marquardt(NELM) algorithm is used for regression between relative permittivity and concentration of inorganic salt categorically. Then, measurement data is processed under modified relative permittivity mixing rule of electrolyte and solvent. Finally the concentration of each component in the multi-component inorganic salt wastewater are obtained. Experimental results show that the maximal relative error (MRE) and average relative error(ARE) of single inorganic salt solution are 1.1% and 0.5%, while mixed solution are 2.6% and 1.89%. Such results indicate significant improvement comparing with previous works. Great potential of RFID in working sewage monitoring is sufficiently confirmed.

Attachable DC Coil Array for Improved Functional MRI at 7T

The prefrontal cortex (PFC) has long been concerned as an important part in cognitive control of neuroscience field. Functional magnetic resonance imaging (fMRI) has been introduced as an effective neuroimaging technique to explore neural activity. However, images within PFC region are subject to susceptibility artifacts, which give rise to undesired image distortion and signal drop-out. In this work, we proposed a method of adding a static magnetic field with high-order spatial pattern for artifact correction. Based on that, a compact attachable 8-channel coil array was constructed. Two toroid chokes were optimized and connected to each coil loop to minimize radiofrequency coupling. To evaluate the array performance, bench measurements and MRI experiments over phantoms and a human subject at 7T were conducted. With the proposed array applied, only 0.3 MHz and 1 MHz frequency shift were introduced to the RF coil, and no apparent RF performance change was observed; the inhomogeneity was reduced by 15%∼24%; in fMRI images over the human subject, “notorious” artifacts within target region were relatively mitigated. The present setup offers a feasible means for practical artifact correction, which is promising for the research that focuses on PFC regions.

Improved CoQ10 Production of Rhodobacter sp. Treated by Atmospheric Pressure Capacitive Coupled Radio Frequency Plasma Jet

Improved CoQ10 Production of Rhodobacter sp. Treated by Atmospheric Pressure Capacitive Coupled Radio Frequency Plasma Jet

Study of the Neon Dielectric Barrier Discharge on a Capacitively Coupled Radio Frequency at a Low Pressure with Metastable Atom Density: Effect of the Pressure

We study the neon dielectric barrier discharge with metastable atom density on a capacitively coupled radio frequency at a pressure of about 4–12 Torr. The transport parameters of neon are dependent on the electron energy, and their range is about 0.04–50 eV. A one-dimensional fluid model and the drift-diffusion theory are used to describe the neon dielectric barrier discharge. The effect of the gas pressure on the properties of neon dielectric barrier discharge is presented for the cycle-averaged regime. It is shown that the particle densities, electric potential, and metastable atom density increase with the pressure. In addition, the surface charge concentration and the gap voltage increase as well.

Substrate-Induced Dissipative and Non-Linear Effects in RF Switches: Probing Ultimate Performance Based on Laser-Machined Membrane Suspension

With the evolution of radio frequency (RF)/microwave technology, there is a demand for circuits that are able to meet highly challenging RF front end specifications. Silicon-on-insulator (SOI) technology is one of the leading platforms for upcoming wireless generation. The degradation of performance due to substrate coupling is a key problem to address for telecommunication circuits, especially for the high throw count switches in RF front ends. In this context, a fast, flexible and local laser ablation technique of the silicon handler allows for the membrane suspension of large millimeter-scale circuits. This approach enables the evaluation of the ultimate performance in the absence of the substrate, i.e., without dissipative losses and substrate-induced non-linear effects, on capacitive comb coupling structures and RF switches. Compared to high-resistivity SOI substrates, the high frequency characterization of RF membrane switches reveals a superior linearity performance with a reduction in second and third harmonics by 17.7 dB and 7.8 dB, respectively. S-parameter analysis also reveals that membrane suspension entails insertion losses that are improved by 0.38 dB and signal reflection lowered by 4 dB due to a reduced off-state capacitance. With reference to a trap-rich substrate, the membrane suspension also achieves an additional 7.8 dB reduction in the second harmonic, indicating that there is still scope for improvement in this figure of merit. The obtained results demonstrate a new way to evaluate optimized circuit performance using post-fabrication substrate engineering.

Diagnostics of RF coupling in H- ion sources as a tool for optimizing source design and operational parameters.

Radio frequency (RF) driven H- ion sources are operated at very high power levels of up 100 kW in order to achieve the desired performance. For the experimental setup, these are demanding conditions possibly limiting the source reliability. Therefore, assessing the optimization potential in terms of RF power losses and the RF power transfer efficiency η to the plasma has moved to the focus of both experimental and numerical modeling investigations at particle accelerator and neutral beam heating sources for fusion plasmas. It has been demonstrated that, e.g., at typical neutral beam injection ion source setups, about half of the RF power provided by the generator is lost in the RF coil and the Faraday shield due to Joule heating or via eddy currents. In a best practice approach, it is exemplarily demonstrated at the ITER RF prototype ion source how experimental evaluation accompanied by numerical modeling of the ion source can be used to improve η. Individual optimization measures regarding the Faraday shield, the RF coil, the discharge geometry, the RF driving frequency, and the application of ferrites are discussed, which could reduce the losses by a factor of two. The provided examples are intended as exemplary guidelines, which can be applied at other setups in order to achieve with low-risk effort an optimized ion source design in terms of reduced losses and hence increased reliability.

Wireless Power Transfer Device Based on RF Energy Circuit and Transformer Coupling Procedure

It is possible to transmit electricity wirelessly without the need for cables. Wireless power transmission makes it possible to link remote places that would otherwise be cut off from access to reliable electricity. A wireless connection to the power supply is expected in the future. This study describes the experimental results of Wireless Power Transfer (WPT) utilizing a transformer coupling approach and its future potential. This WPT device (WPTD) is used to transmit power using two procedures of energy transfer: radiofrequency coupling and transformer coupling, both of which are magnetic based, in principle. The distance between the transmitter and receiver of the system affects the amount of power that can be sent. Research is performed to establish how far apart the system's transmitter and receiver should be. Magnetic fields may transmit energy between two coils, but the distance between the two coils must be too close for this approach to work. Aside from that, it assesses the setting parameter of a value that has been tabulated using a certain application, in the findings and discussion parts.

Constructive Quantum Interference in Photochemical Reactions.

Interferences emerge when multiple pathways coexist together, leading toward the same result. Here, we report a theoretical study for a reaction scheme that leads to constructive quantum interference in a photoassociation (PA) reaction of a 87Rb Bose-Einstein condensate where the reactant spin state is prepared in a coherent superposition of multiple bare spin states. This is achieved by changing the reactive scattering channel in the PA reaction. As the origin of coherent control comes from the spin part of the wavefunction, we show that it is sufficient to use radio frequency (RF) coupling to achieve the superposition state. We simulate the RF coupling on a quantum processor (IBMQ Lima), and our results show that interferences can be used as a resource for the coherent control of photochemical reactions. The approach is general and can be employed to study a wide spectrum of chemical reactions in the ultracold regime.

An Electrical Impedance-Based Technique to Infer Plasma Density in a 13.56-MHz Magnetized Capacitive Coupled RF Discharge

Plasma density in a magnetized, capacitive-coupled, radio frequency (RF) discharge has been determined using the electrical impedance characteristics of the discharge. The effective impedance between the parallel plate electrodes has been treated as an equivalent electric circuit consisting of resistive and reactive components, expressed in terms of high-frequency plasma conductivity. Hence the model is used to connect the externally measured RF voltage, current, and their relative phase to plasma density. Additionally, a triple Langmuir probe (TLP) is used to substantiate the results of the electrical impedance model. The plasma density obtained using the direct probe measurement is found to be in good agreement with those determined from the passive measurements based on electrical impedance of the discharge as outlined in this article.

Radio-frequency evaporation in an optical dipole trap

We present an evaporative cooling technique for atoms trapped in an optical dipole trap that benefits from narrow optical transitions. For an appropriate choice of wavelength and polarization, a single laser beam leads to opposite light shifts in two internal states of the lowest-energy manifold. Radio-frequency coupling between these two states results in evaporative cooling at a constant trap stiffness. The evaporation protocol is well adapted to several atomic species, in particular to the case of Lanthanides such as Er, Dy, and fermionic Yb, but also to alkali-earth metals such as fermionic Sr. We derive the dimensionless expressions that allow us to estimate the evaporation efficiency. As a concrete example, we consider the case of $^{162}\mathrm{Dy}$ and present a numerical analysis of the evaporation in a dipole trap near the ${J}^{\ensuremath{'}}=J$ optical transition at $832\phantom{\rule{0.16em}{0ex}}\mathrm{n}\mathrm{m}$. We show that this technique can lead to runaway evaporation in a minimalist experimental setup.

Design and development of radio frequency system for pulse positron low energy beam and its electron beam trials

Details of the design and development of radio frequency (RF) system at 37.5 MHz and 150 MHz and initial test results of electron beam trials of a pulsed positron beam line being developed at BARC, Mumbai are presented in this paper. The RF part of the beam line is based on the conventional positron pulsing technique of chopper-pre buncher-buncher arrangement. Picosecond (ps) pulsing is achieved by a 150 MHz quarter wave resonator, which times focuses the chopped positron beam onto the sample. The chopper and pre buncher, preceding the buncher, are designed to operate at one-fourth of the frequency of the buncher. The reflection type grid chopper uses sinusoidal waves riding on a DC offset to chop the incoming beam into less than 2 ns pulses. These various structures were excited by the RF power coupled from an overall two frequency RF system. This RF system comprises of amplifiers at 37.5 MHz and 150 MHz that derive a single common input from an arbitrary frequency generator (AFG) to reduce the timing distortion, their respective impedance matching units and RF coupling lines made of RF components used for amplitude and phase adjustments and then, feeds the RF power to these structures. The RF system was initially tested on a prototype setup before incorporating in the main pulsed positron beam line. RF interference suppression techniques like filtering and shielding were used to ensure minimum interference between RF signals and the various detector electronics. Before positron beam trials, electron beam trials were performed in the positron beam line. A final pulse width 280 ps was measured with an electron beam.