Radio Frequency Research Articles

Efficiency scaling of inductively coupled plasmas for radio frequency propulsion systems

AbstractA generalized inductively coupled plasma (ICP) efficiency model is derived, which may be used to predict plasma generation efficiency with many types of radio frequency (RF) electric propulsion system. The analytical ICP discharge model is used to examine device scaling, and investigate trends in ICP performance as a function of geometry and system inputs. The ICP efficiency model is applied to an analytical RF cathode model to predict device behavior. Results from the updated RF cathode model show improvements in agreement with experimental data.

Numerical model of N-level cascade systems for atomic Radio Frequency sensing applications

AbstractA ready-to-use numerical model has been developed for the atomic ladder (cascade) systems which are widely exploited in Rydberg Radio Frequency (RF) sensors. The model has been explicitly designed for user convenience and to be extensible to arbitrary N-level non-thermal systems. The versatility and adaptability of the model is validated up to 4-level atomic systems by direct comparison with experimental results from the prior art. The numerical model provides a good approximation to the experimental results and provides experimentalists with a convenient ready-to-use model to optimise the operation of an N-level Rydberg RF sensor. Current sensors exploit the 4-level atomic systems based on alkali metal atoms which require visible frequency lasers and these can be expensive and also suffer from high attenuation within optical fiber. The ability to quickly and simply explore more complex N-level systems offers the potential to use cheaper and lower-loss near-infrared lasers.

Submyocardial Pacing Threshold Distribution During Cold Saline Application; Exploring Reversible Arrhythmia Inhibition.

Cold saline application through an irrigation catheter may induce reversible inhibition of submyocardial excitation, which may be used to identify in advance an ideal site for radiofrequency (RF) energy delivery around delicate areas. An open irrigation catheter was positioned vertically or parallel with 10-g contact on coronary perfusing porcine hearts and the contacted myocardium was cooled by cold saline at 4°C (20mL/min). A temperature electrode was inserted 2mm below the myocardial surface (intra-myocardial temperature at approximately 2 mm below the surface [Temp-BS]). Pacing threshold inside the ventricular wall was measured using aneight-pole electrode plunge needle inserted 5-8mm close to the ablation catheter, and percent increase of the pacing threshold by the cold saline application (%increase-PT) was calculated. During cooling, pacing at 10V from the myocardial surface interrupted constant capture in 7/10 experiments in vertical and in 9/10 experiments in parallel ablation catheter contact. Minimum Temp-BS was not different in both catheter contact positions (25.9±4.0°C in vertical vs. 25.4±2.6°C in parallel). Large % increase-PT on the surface myocardium decreased as the myocardial depth became deeper, and > 150% increase was at a depth approximately 2-3mm from the surface and > 120% increase around 6-7mm from the surface. After cessation of cold saline application, the increased %increase-PT recovered to the pre-cooling values. Cold saline application through an irrigation catheter reversibly inhibited submyocardial excitation. This simple method may have the potential to pre-determine the ideal ablation site in sensitive areas of the heart, although further studies and technological adjustments are required before clinical use.

Efficacy of Monopolar Radiofrequency or Microwave Ablation in Intrahepatic Cholangiocarcinoma: A Retrospective Multicenter Study from Association des Gastro-Entérologues Oncologues (AGEO)

Background: Several locoregional treatments approaches, including thermoablation, have been tested for the treatment of intrahepatic cholangiocarcinoma (ICC) and have shown encouraging results. However, data are heterogeneous in terms of tumor number, size, and ablation technique. Objective: The aim of this study was to investigate the efficacy and prognostic factors in ICC treated by monopolar radiofrequency (RF) or microwave ablation (MW). Methods: This was a retrospective study including patients treated with RF or MW for ICC in six participating centers. DFS and OS were evaluated by the Kaplan–Meier method and prognostic factors by log-rank test and Cox modeling. Results: From January 2015 to October 2023, 24 patients with 31 nodules were treated with RFA or MW. Overall, 70% had chronic liver disease, with 50% at cirrhosis stage. The median size of lesions was 17 mm (6–35 mm). After a median follow-up of 33 months (5–85), the median DFS was 10.5 months. The median OS was 40.8 months. On univariate and multivariate analysis, only lesion size > 17 mm was associated with a poor OS (HR 3.09; IC [1.02; 9.37] (p = 0.04). Conclusions: Monopolar radiofrequency or microwave ablation is an alternative to surgery for small ICCs. Tumors < 17 mm were associated with better OS.

Scientific and technical ways of reducing quantitative indicators of false alarms during the operation of an airboard radar station on the background of the underlying surface (earth)

The purpose of the research is development of scientific and technical ways to reduce the quantitative indicators of false alarms when operating an on-board radar station against the background of the underlying surface (earth) against the background of passive interference.Methods. When conducting scientific research, methods of probability theory, mathematical statistics, statistical radio engineering and computational mathematics were used. The study identified a number of methods and technical solutions based on them that make it possible to increase the efficiency of the functioning of airborne radar stations against the background of passive interference. The paper proposes a method for expanding the signal spectrum to 1 GHz by reducing the resolved volume of airborne radar stations. Physically, this is determined by the fact that with a decrease in the resolved volume, the size of the underlying surface area from which the signal is reflected decreases. In order to improve the quality of detection of objects against the background of the underlying surface, a method of using polarization modes is proposed.Results. In the course of the research: a technical solution was proposed based on the method of expanding the signal spectrum to 1 GHz by reducing the resolution volume of airborne radar stations designed to convert radio frequency signals into digital form, using a mixed signal receiver with direct digitization at radio frequency, such as the AD6688 ; a design of a low-baseline radar system has been developed, consisting of two positions, the antennas of which are located within the average width of the lobe of the backscattering diagram of the irradiated object; a feature of the antenna is the ability to receive and emit signals of the same linear polarization, but orthogonal to the polarization of the first position (including . horizontal and vertical polarization signals); an important relation was obtained for a lowbaseline polarization measuring system (MPIS) when the distance between two partial antennas can be much less than the distance to the measured object. Conclusion. The scientific article proposes methods and technical solutions based on these methods to reduce the quantitative indicators of false alarms when operating an on-board radar station against the background of the underlying surface (ground) against the background of passive interference. The proposed approach allows us to move on to the synthesis of a low-baseline polarization measuring system.

Positioning Sensor Data Mining and Correlation Analysis Based on Multi-mode Radio Frequency Identification

Real-time positioning and sensor data mining are critical for various Internet of things (IoT) applications, but current approaches face challenges such as limited accuracy, high cost, and energy inefficiency. This paper proposes a novel fusion intelligent structure that combines radio frequency identification (RFID) technology and wireless sensor networks (WSN) to enable accurate and efficient positioning and data mining. The proposed method consists of two key components: an energy heterogeneity strategy for optimizing network energy consumption, and a data association feature analysis technique for mining sensor data. The results demonstrated that the proposed approach achieved superior positioning accuracy compared to other algorithms, with an average error of less than 0.300 under various conditions. The data detection accuracy was also high, with a maximum false detection rate of 3%. Furthermore, the proposed energy heterogeneity strategy significantly improved network energy utilization and stability. Real-world scenario testing validated the practicality of the proposed approach, with an average positioning error of less than 0.500 meters. These results validate the effectiveness of the proposed RFID-WSN fusion structure for real-time positioning and sensor data mining, providing a promising solution for IoT applications.

Design of multi-row parallel-transmit coil arrays for enhanced SAR efficiency with deep brain electrodes at 3T: an electromagnetic simulation study.

Tissue heating near the implanted deep brain stimulation (DBS) during magnetic resonance imaging (MRI) poses a significant safety constraint. This study aimed to evaluate the performance of parallel transmit (pTx) head transmit radiofrequency (RF) coils in DBS patients, with a focus on excitation fidelity under specific absorption rate (SAR) control for brain imaging at 3T MRI. We employed electromagnetic simulations to assess different coil configurations, including multi-row pTx coils of 16-24 channels arranged in 1, 2, and 3 rows, and compared these to a circularly polarised and pTx birdcage coil using a realistic human model without and with DBS leads and electrodes. Two- and three-row pTx coils with overlapping loop elements exhibited similar performance, which was superior in excitation homogeneity and local SAR compared to the single-row coil and the birdcage coil both without and with DBS. These findings suggest that multi-row coils can enhance the safety and efficacy of MRI in patients with DBS devices, so potentially improving imaging performance in this expanding patient population. There was a minimal difference in performance between the 2 and 3-row coils, favouring the simpler, lower channel count design for practical implementation.

Lesion characteristics of long application time ablation using unipolar half-normal saline irrigation and bipolar normal saline irrigation.

Unipolar radiofrequency (RF) ablation using half-normal saline irrigation (UNIP-HNS) and bipolar RF ablation using normal saline irrigation (BIP-NS) are effective to treat arrhythmias from inside thick myocardium. However, differences between these two ablations when using a long application time had not fully been studied. UNIP-HNS, BIP-NS and unipolar RF ablation using normal saline irrigation (UNIP-NS) were applied for 120 seconds (30 W and 20-g contact) to porcine endocardial wall (≧15.0 mm thickness). All ablations (30 applications each in UNIP-HNS and BIP-NS, and 20 applications in UNIP-NS) were successfully accomplished without steam-pop. Total impedance decline was largest in BIP-NS followed by UNIP-HNS and UNIP-NS. UNIP-HNS created larger surface lesions and greater maximum lesion width under the surface than those by UNIP-NS and BIP-NS. Endocardial lesion depth in UNIP-HNS and BIP-NS were deeper than that in UNIP-NS, but with no difference between UNIP-HNS and BIP-NS, when selecting non-transmural lesions. Similar results were obtained when all lesions (non-transmural and transmural) were included and endocardial lesion depth of the transmural lesions (13/30 applications of BIP-NS) was estimated as 50% of the myocardial thickness. Lesion length in the transverse myocardial wall (endocardial plus epicardial lesions) was greatest in BIP-NS. Longer application time ablation (30 W) targeting the thick myocardium was performable in UNIP-HNS and BIP-NS. Since a transmural lesion and/or a deeper lesion into the myocardial wall are created, BIP-NS is preferable if two ablation catheters can be positioned on either side of the target.

Computer Modeling Study of the Effects of Radio Frequency EM Radiation on Humans

Computer Modeling Study of the Effects of Radio Frequency EM Radiation on Humans

Suppression of Short-Channel Effects in AlGaN/GaN HEMTs Using SiNx Stress-Engineered Technique

In this work, we present the novel application of SiNx stress-engineering techniques for the suppression of short-channel effects in AlGaN/GaN high-electron-mobility transistors (HEMTs), accompanied by a comprehensive analysis of the underlying mechanisms. The compressive stress SiNx passivation significantly enhances the barrier height at the heterojunction beneath the gate, maintaining it above the quasi-Fermi level even as Vds rises to 20 V. As a result, in GaN devices with a gate length of 160 nm, the devices with compressive stress SiNx passivation exhibit significantly lower drain-induced barrier lowering (DIBL) factors of 2.25 mV/V, 2.56 mV/V, 4.71 mV/V, and 3.84 mV/V corresponding to drain bias voltages of 5 V, 10 V, 15 V, and 20 V, respectively. Furthermore, as Vds increases, there is an insignificant degradation in transconductance, subthreshold swing, leakage current, or output conductance. In contrast, the devices with stress-free passivation show relatively higher DIBL factors (greater than 20 mV/V) and substantial degradation in pinch-off performance and output characteristics. These results demonstrate that the SiNx stress-engineering technique is an attractive technique to facilitate high-performance and high-reliability GaN-based HEMTs for radio frequency (RF) electronics applications.

Enhancing activated carbon supercapacitor electrodes using sputtered Cu-doped BiFeO3 thin films.

This work describes the fabrication of a composite supercapacitor electrode made of Cu-doped BiFeO (Cu-BFO) films on an activated carbon (AC) electrode using radio-frequency (RF) magnetron sputtering. To prevent exfoliation of Cu-BFO and AC upon immersion in an electrolyte, the nickel foam sandwiching electrode technique was introduced. The Cu-BFO films significantly enhanced electrochemical properties, increasing specific capacitance by up to 151% compared to that of an AC electrode. This was attributed to Faradaic reactions and specific surface area in the Cu-BFO/AC electrode. The highest specific capacitance achieved was 169 F at 0.5 A , and cycling stability retention was 93.12% after 500 cycles. However, the remaining percentage of the specific capacitance decreased differently with increasing thickness, which is also discussed. Furthermore, an asymmetric supercapacitor using Cu-BFO/AC and AC electrodes demonstrated a high energy density of 4.71 Wh , power density of 2.66 kW , and over 90% retention after 1000 cycles, highlighting its durability. The uniform RF magnetron sputtering deposition is vital for mass production. Combined with impressive retention in asymmetric supercapacitors, this scalability suggests a promising pathway for large-scale manufacturing. Consequently, this work could pave the way for the large-scale production of supercapacitors.

Orientation-independent quantification of macromolecular proton fraction in tissues with suppression of residual dipolar coupling.

Quantitative magnetization transfer (MT) imaging enables noninvasive characterization of the macromolecular environment of tissues. However, recent work has highlighted that the quantification of MT parameters using saturation radiofrequency (RF) pulses exhibits orientation dependence in ordered tissue structures, potentially confounding its clinical applications. Notably, in tissues with ordered structures, such as articular cartilage and myelin, the residual dipolar coupling (RDC) effect can arise owing to incomplete averaging of dipolar-dipolar interactions of water protons. In this study, we demonstrated the confounding effect of RDC on quantitative MT imaging in ordered tissues can be suppressed by using an emerging technique known as macromolecular proton fraction mapping based on spin-lock (MPF-SL). The off-resonance spin-lock RF pulse in MPF-SL could be designed to generate a strong effective spin-lock field to suppress RDC without violating the specific absorption rate and hardware limitations in clinical scans. Furthermore, suppressing the water pool contribution in MPF-SL enabled the application of a strong effective spin-lock field without confounding effects from direct water saturation. Our findings were experimentally validated using human knee specimens and healthy human cartilage. The results demonstrated that MPF-SL exhibits lower sensitivity to tissue orientation compared with , , and saturation-pulse-based MT imaging. Consequently, MPF-SL could serve as a valuable orientation-independent technique for the quantification of MPF.

On the Effect of Randomly Oriented Grain Growth on the Structure of Aluminum Thin Films Deposited via Magnetron Sputtering

The microstructure of aluminum thin films, including the grain morphology and surface roughness, are key parameters for improving the thermal or electrical properties and optical reflectance of films. The first step in optimizing these parameters is a thorough understanding of the grain growth mechanisms and film structure. To investigate these issues, thin aluminum films with thicknesses ranging from 25 to 280 nm were coated on SiOx/Si substrates at ambient temperature under high-vacuum conditions and a low argon pressure of 3 × 10−3 mbar (0.3 Pa) using the radio frequency magnetron sputtering method. Quantitative analyses of the surface roughness and nanograin characteristics were conducted using atomic force microscopy (AFM), transmission electron microscopy (TEM), and X-ray diffraction. Changes in specular reflectance were measured using ultraviolet–visible and near-infrared spectroscopy. The low roughness values obtained from the AFM images resulted in high film reflectivity, even for thicker films. TEM and AFM results indicate monomodal, randomly oriented grain growth without a distinct columnar or spherical morphology. Using TEM cross-sectional images and the dependence of the grain size on the film thickness, we propose a grain growth mechanism based on the diffusion mobility of aluminum atoms through grain boundaries.

Tunable and Reconfigurable Fundamental, Frequency-Doubled and Dual-Frequency RF Signal Generator

Tunable and Reconfigurable Fundamental, Frequency-Doubled and Dual-Frequency RF Signal Generator

Lithium lanthanum zirconate thin films investigated using spectroscopic and microscopic techniques

ABSTRACT In this work, thin film growth of lithium lanthanum zirconate (LLZO) on p-type Si substrate was carried out using radio frequency (RF) sputtering and was characterized using microscopic and various spectroscopic techniques including X-ray absorption spectroscopy. Films were deposited at a sputtering power of 70 W at a based pressure of 4 × 10−5 Torr. Deposited films were annealed at 700°C for 1 h. The as-deposited films were amorphous and no transition to a crystalline phase was observed after annealing. Although films are amorphous Raman spectroscopic measurements exhibit the bands that are characteristics of LLZO. The thickness of the as-deposited film estimated from Rutherford backscattering spectroscopy (RBS) was 100 nm and remained unchanged after annealing. The thickness of the annealed films as determined from scanning electron microscopy (SEM) was 48 ± 21 nm. The composition of these films determined from RBS is almost analogues to that estimated from SEM-energy-dispersive spectroscopic measurements. However, O K-edge near edge X-ray absorption fine structure spectra showed slight modification with annealing but a drastic change was observed in the spectra measured in total electron yield and total fluorescence yield measurements. This change is due to the difference like the interaction of oxygen ions with its neighbouring atoms on the surface and in the bulk of the films.

Triple-Stacked FET Distributed Power Amplifier Using 28 nm CMOS Process

A broadband 28 nm complementary metal–oxide–semiconductor (CMOS) power amplifier was implemented using a distributed amplification design. To develop a model library for high-frequency design, various test patterns for active and passive elements were fabricated and compared through measurements. As a result, a symmetrical n-channel field-effect transistor (NFET) was used as the active device, and a co-planar waveguide (CPW) with floating bottom metal layers was chosen as the transmission line for the passive element. These choices demonstrated superior radio frequency (RF) characteristics at high frequencies compared to other device candidates. Furthermore, to address the low breakdown voltage of CMOS, a triple-stacked FET structure was designed as the gain cell of the distributed power amplifier (DPA). The fabricated DPA showed a maximum small-signal gain of 22 dB and a minimum of 10 dB from DC to 56 GHz, with a maximum saturated output power of 20 dBm and a minimum of 13 dBm from 1 to 39 GHz. Notably, these results were achieved on the first attempt by designing solely based on measurement data from the test patterns.

Abstract 4136869: Time Course and Predictors of PVC Recurrence After Acutely Successful Catheter Ablation

Introduction: In prior studies, predictors of long-term success following acutely successful radiofrequency (RF) ablation have included female-sex, single-PVC morphology and EGM-QRS > 24ms. Time course and predictors of PVC recurrence following acutely successful ablation has been less well documented. Use of extended ambulatory monitoring in the immediate post-procedural period can help to identify those with early recurrence. Goals: To define time to recurrence and predictors of recurrence of PVCs after RF ablation following acutely successful ablation. Methods: Consecutive patients from January 1 st , 2016 through December 31 st , 2023 undergoing PVC ablation with available post-ablation extended ambulatory monitoring (Zio, iRhythm, San Francisco, CA) were retrospectively analyzed. Recurrence was defined as an increase in PVC burden to >5% during monitoring after acute success or failure to have sustained reduction in PVC burden of >80%. Acute success was defined as elimination of the targeted PVC after the last ablation lesion. Long-term succes was defined as absence of targeted PVC's during all follow-up visits and PVC-burden < 5% on follow-up monitoring. Results: Among 121 patients who underwent successful PVC ablation, 101 (83.4%) had long-term success and 20 (17%) had recurrence. Patients with recurrence were older (62.4 ± 12 vs 55 ± 13., p = 0.019), had a higher incidence of CAD (13 (13%) vs 9 (45%), p = 0.001) and CHF (40 (40%) vs 15 (75%), p = 0.004). At time of ablation, the recurrence group was also more likely to have >1 PVC morphology (6 (6%) vs 8 (40%), p = <0.001). Location and earliest activation time of the predominant PVC were not assocated with likelihood of recurrence. Within the recurrence group, 13 (65%) had recurrence in the immediate 2 week post-procedural period with an average time to recurrence of 3.9 days. Conclusion: Recurrence occured in slightly less than 20% of cases with a relatively high proportion of those occuring within the immediate 2 week post-procedural period during extended ambulatory monitoring. The presence of greater than 1 PVC morphology at time of ablation is a risk factor for recurrence suggesting a higher likelihood of acute suppression without durable resolution in those instances.

Proton bunch monitors for the clinical translation of prompt gamma-ray timing

Objective. Prompt gamma-ray timing is an emerging technology in the field of particle therapy treatment verification. This system measures the arrival times of gamma rays produced in the patient body and uses the cyclotron radio frequency signal as time reference for the beam micro-bunches. Its translation into clinical practice is currently hindered by observed instabilities in the phase relation between the cyclotron radio frequency and the measured arrival time of prompt gamma rays. To counteract this, two proton bunch monitors are presented, integrated into the prompt gamma-ray timing workflow and evaluated.Approach. The two monitors are (a) a diamond detector placed at the beam energy degrader, and (b) a cyclotron monitor signal measuring the phase difference between dee current and voltage. First, the two proton bunch monitors as well as their mutual correlation were characterized. Then, a prompt gamma-ray timing measurement was performed aiming to quantify the present magnitude of the phase instabilities and to evaluate the ability of the proton bunch monitors to correct for these instabilities.Main results. It was found that the two new monitors showed a very high correlation for intermediate proton energies after the first second of irradiation, and that they were able to reduce fluctuations in the detected phase of prompt gamma rays. Furthermore, the amplitude of the phase instabilities had intrinsically decreased from about 700 ps to below 100 ps due to cyclotron upgrades.Significance. The uncertainty of the prompt gamma-ray timing method for proton treatment verification was reduced. For routine clinical application, challenges remain in accounting for detector load effects, temperature drifts and throughput limitations.

ICRF resonance cones in the low-density scrape-off-layer of ASDEX Upgrade

Abstract The ICRF slow wave is a potential carrier for parallel RF electric fields known to cause unwanted plasma-wall interactions in magnetic confinement fusion experiments.
In nowadays machines the slow wave is usually confined to the far scrape-off layer or the limiter shadow, but conditions in future experiments and reactors may allow the slow wave to be propagative in a larger region.

Simulations with RAPLICASOL for various geometries show that the ICRF slow waves appear as the so-called resonance cones characterized by large localized electric fields.
The resonance cones emerge from the points along the plasma-antenna interface where (in the cold plasma approximation) the radio frequency electric field diverges.
We demonstrate that in the parameter range of interest, the propagation of the resonance cones in a plasma with a density gradient is defined by a simple geometric model, using the local plasma density and the frequency as input parameters.
In the context of experiments at ASDEX Upgrade, simulations illustrate that the resonance cones can emerge from a single tile of the ICRF antenna limiter.
Experiments at the Ion-cyclotron System Hardware Test ARrangement (ISHTAR) were conducted to test the detection principle in a simple environment.
In agreement with simulations and with predicted characteristics which depend on operation parameters, the resonance cones are excited by an RF antenna and propagate through the relatively homogeneous plasma in ISHTAR. 
The cones are detected at a distance from the antenna using two probes scanning through the plasma.
In ASDEX Upgrade, a single tile of an antenna limiter was modified to launch RF power into a specially tailored low-density scrape-off layer.
Probes at the midplane manipulator were then used to detect the wave electric fields at a distance from the RF source.
The detected RF signals show that the signal maxima are located close to the lower hybrid resonance density and are highest when the source and the probes are connected along magnetic field lines.
These observations agrees with the model for resonance cones from the simulations.

A Radio Frequency Interference Screening Framework—From Quick-Look Detection Using Statistics-Assisted Network to Raw Echo Tracing

Synthetic aperture radar (SAR) is often affected by other high-power electromagnetic devices during ground observation, which causes unintentional radio frequency interference (RFI) with the acquired echo, bringing adverse effects into data processing and image interpretation. When faced with the task of screening massive SAR data, there is an urgent need for the global perception and detection of interference. The existing RFI detection method usually only uses a single type of data for detection, ignoring the information association between the data at all levels of the real SAR product, resulting in some computational redundancy. Meanwhile, current deep learning-based algorithms are often unable to locate the range of RFI coverage in the azimuth direction. Therefore, a novel RFI processing framework from quick-looks to single-look complex (SLC) data and then to raw echo is proposed. We take the data of Sentinel-1 terrain observation with progressive scan (TOPS) mode as an example. By combining the statistics-assisted network with the sliding-window algorithm and the error-tolerant training strategy, it is possible to accurately detect and locate RFI in the quick looks of an SLC product. Then, through the analysis of the TOPSAR imaging principle, the position of the RFI in the SLC image is preliminarily confirmed. The possible distribution of the RFI in the corresponding raw echo is further inferred, which is one of the first attempts to use spaceborne SAR data to ‌elucidate the RFI location mapping relationship between image data and raw echo. Compared with directly detecting all of the SLC data, the time for the proposed framework to determine the RFI distribution in the SLC data can be shortened by 53.526%. All the research in this paper is conducted on Sentinel-1 real data, which verify the feasibility and effectiveness of the proposed framework for radio frequency signals monitoring in advanced spaceborne SAR systems.