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We are developing a new instrument, the RF Josephson arbitrary waveform synthesizer (RF-JAWS), for communications metrology and quantum information applications. An important aspect of the RF-JAWS design is the accurate and traceable characterization of its superconducting devices. In this article, we present a procedure for characterizing microwave superconducting devices in a cryogenic RF probe station via a vector network analyzer (VNA) calibrated with a custom cryogenic calibration kit colocated with the superconducting device under test (DUT) in the cryogenic environment. By de-embedding lossy and dispersive RF interconnects linking the superconducting DUT to the measurement apparatus at room temperature, we characterize the DUT exactly at the cryogenic on-wafer reference plane. More importantly, we operate our VNA with an external modulated source and our procedure features metrology-grade multiline thru-reflect-line calibration and absolute power and phase corrections, as opposed to the more common relative scattering-parameter correction. In addition, we apply an X -parameter model to account for impedance mismatch in cryogenic Josephson microwave sources. Our techniques are also suitable for cryogenic characterization of microwave superconducting devices for solid-state quantum computers and could help to optimize the quantum-classical interfaces in these systems.

The experimental realization of the two-frequency 14N nuclear quadrupole resonance (NQR) technique with use of the gradiometer radiofrequency (RF) probe for applications in the remote detection of explosives and other substances has been proposed. The planar two-frequency gradiometer has been designed, modeled and manufactured. The regions, where the RF magnetic fields are nearly orthogonal to each other, have been determined by finite-element modeling studies. The two-frequency experiments have been carried out for the detection of hexahydro-1,3,5-trinitro-s-triazine C3H6N6O6 (RDX). The possibility of the combined use of the two-frequency 14N NQR technique and the gradiometer RF probe in practice for detection of explosives hidden under clothes or underground has been also discussed.

In this work, amine-carbon quantum dots (CQDs)/rhodamine B (RhB) ratiometric fluorescent (RF) sensor was employed for effective and selective determination of tamsulosin hydrochloride (TMS) based on a dual-emission fluorescence system. Although the function of amine-CQDs is to transfer the specific interaction between TMS and sensor into detectable fluorescence (FL) signals, RhB as a reference unit has been employed to omit internal and external effects. The FL signal was quenched by adding the TMS at 442 nm; nevertheless, it did not change at 569 nm. The material characterization and investigation of the sensing mechanism were done. The optimization of pH, the volumetric ratio of CQDs to RhB, and interaction time parameters were carried out by the one-variable-at-a-time (OVAT) method. The quantitative analysis of the concentration of TMS for this RF sensor in a linear range of 0.446–7.083 μg mL−1 (1.091–17.338 μM) was obtained (R2 = 0.9969, n = 3) under optimum conditions. The limit of detection and quantitation values were estimated to be 0.033 μg mL−1 (0.081 μM) and 0.109 μg mL−1 (0.267 μM), respectively. The repeatability of intra-day and inter-day were less than one percent. This inexpensive RF probe was well applied to determine TMS in biological fluids, and acceptable achievements were obtained.

PURPOSE: The use of surface radiofrequency (RF) coils is common practice to boost sensitivity in (pre)clinical MRI. The number of transceive surface RF coils is rapidly growing due to the surge in cryogenically cooled RF technology and ultrahigh‐field MRI. Consequently, there is an increasing need for effective correction of the excitation field (B(1)(+)) inhomogeneity inherent in these coils. Retrospective B(1) correction permits quantitative MRI, but this usually requires a pulse sequence‐specific analytical signal intensity (SI) equation. Such an equation is not available for fast spin‐echo (Rapid Acquisition with Relaxation Enhancement, RARE) MRI. Here we present, test, and validate retrospective B(1) correction methods for RARE. METHODS: We implemented the commonly used sensitivity correction and developed an empirical model‐based method and a hybrid combination of both. Tests and validations were performed with a cryogenically cooled RF probe and a single‐loop RF coil. Accuracy of SI quantification and T(1) contrast were evaluated after correction. RESULTS: The three described correction methods achieved dramatic improvements in B(1) homogeneity and significantly improved SI quantification and T(1) contrast, with mean SI errors reduced from >40% to >10% following correction in all cases. Upon correction, images of phantoms and mouse heads demonstrated homogeneity comparable to that of images acquired with a volume resonator. This was quantified by SI profile, SI ratio (error 80% in vivo and ex vivo compared to PIU > 87% with the reference RF coil). CONCLUSIONS: This work demonstrates the efficacy of three B(1) correction methods tailored for transceive surface RF probes and RARE MRI. The corrected images are suitable for quantification and show comparable results between the three methods, opening the way for T(1) measurements and X‐nuclei quantification using surface transceiver RF coils. This approach is applicable to other MR techniques for which no analytical SI exists.

This paper describes three-dimensional numerical simulations and Radio Frequency (RF) measurements of wave propagation in microwave-heated magnetized plasmas of ion sources. Full-wave solution of Maxwell's equations has been addressed through the Finite Element Method (FEM) commercial software COMSOL. Our numerical model takes into account the strongly inhomogeneous and anisotropic magnetized "cold" plasma medium. The simulations reproduce the main features of the wave-plasma interaction of the Flexible Plasma Trap (FPT) that recently came into operations at INFN-LNS. A two-pins RF probe has been ad-hoc developed and used as a plasmaimmersed antenna for measuring local wave electric fields in the FPT device. The measurements of plasma electron density and RF electric field, performed for different external magnetic field configuration, allowed a direct comparison with the assumed simulation model.

A prototype RF probe card is assembled to test the feasibility of Pogo-pins as robust probe tips for the automized testing of multiple-port millimeter-wave circuits. A custom-made ceramic housing machined from a low-loss dielectric holds an array of 157 Pogo-pins, each with 2.9 mm-length in fixed positions. The ceramic housing is then mounted onto a probe-card PCB for power-loss measurements on two signal-ground Pogo-pin connections arbitrarily selected from the array. The probing results on a test circuit with a simple thru-line indicate a successful power transfer with a small insertion loss of less than 0.5 dB per single Pogo-pin connection up to 25 GHz. A new probe card design using shorter Pogo-pins is being prepared to extend the operation frequency to beyond 40 GHz.

Radiofrequency ablation of the renal tumors considered the least invasive technique to get rid of malignancies cells. High-frequency waves in the range of 0.9 – 2.5 GHz were applied to the cancerous cells. Consequently, resistive heating was generated used to destroy the cancerous cells. In this paper, this technique had been applied to a 3D accurate model of the kidney with similar dimensions and shape including its artery, vein, and ureter. The next step was to design an RF probe to get high values of specific absorption rate for the cancerous cells and minimum values for the normal cells of the kidney. Simulation results showed that the shape of the model has the greatest effect on the resulting lesion volume and shape. In this work, the internally cooled electrode using Gil was designed from aluminum material with its tines revolved to 270° and Gaussian signal as the excitation signal.

A high-temperature superconducting (HTS) radio frequency (RF) probe has been designed for nuclear magnetic resonance spectroscopy that is constructed of two newly developed HTS elliptical–coupled resonators that are placed on either side of the sample. The probe has a higher quality factor and a more uniform magnetic field along the z -axis than one with square resonators. The measured unloaded quality factor ( Qu ) of a pair of elliptical–coupled resonators fabricated using YBa2Cu3Oy thin films on an Al2O3 substrate was about 30 000 at 15 K, which is about 82 times higher than the simulated Qu of a copper counterpart at room temperature. Measurement of the input power dependence of Qu showed that a Qu of over 20 000 was obtained up to 16 dBm. Measurement of the RF magnetic field profile along the z -axis showed that the RF magnetic field was more than 85% uniform around the sample region.

Antenna tests require precise positioning of an RF probe — at rest and during dynamic motions. Positioning includes the actual position of the tip of this probe and its vectorial orientation. This paper presents the automation and control concept for a novel crane-based measurement system. The system consists of a measurement gondola mounted to the hook of an overhead crane and designed such that it carries the probe and rotates it about two orthogonal axes. This system allows to arbitrarily position and orientate the probe in space on a given scanning surface. As the gondola is positioned using a crane, sway, skew, and tilting oscillations must be taken into account. Therefore a control concept is proposed that extends standard crane control by two additional degrees of freedom. For motion control with good trajectory tracking behavior, a flatness-based two-degree-of-freedom (2-DOF) state controller is applied for each axis. An extended Kalman filter is used for state estimation so that nonlinear effects and coupling between different axes are considered. The effectiveness of the proposed control concept is demonstrated by means of experimental results.

Background: Radiofrequency ablation (RF) is already a viable alternative to surgical resection for focal liver tumors treatment. The use of RF ablation in combination with surgery or chemotherapy and the large panel of RF tools need new experimental models to develop new opportunities for this kind of therapy. Purpose: The purpose of this study was to identify the optimal RF parameters that will allow in situ colic cancer liver metastases destruction with minimal secondary effects. Materials and Methods: The CC531s colic cancer tumor cells were used to induce liver metastases in 30 synergic Wag/Rij rats. When metastases reached at least 1 cm in diameter, RF generator RITA 1500X, and expandable tip RF probe Starburst SDE (Angiodynamics, USA) was used for the RF ablation. The animal survival rate and the RF-induced lesions have been studied, while only the generator delivered power has been modified (90W, 20W, and 10W, respectively). Results: Survival was significantly low in the group with 90W-delivered power RF. Moreover, statistically significant differences were revealed between groups with high and low RF power, regarding the morphological changes of the liver parenchyma and the adjacent organs, without significant difference on the RF therapeutically effect. Conclusions: In an experimental setting, an increased RF generator power induces important lesions of the abdominal organs with subsequently important mortality rate, without improving the RF therapeutic efficiency.

In this paper, we present a guideline to optimize the layout floorplan by minimizing the impact of on-wafer neighbouring structures in very high frequency (1 GHz to 220 GHz) on-wafer measurements of Si electronic devices. To present the guideline, a 3D electromagnetic (EM) simulation is carried out extensively using a realistic EM model of a commercial RF probe. First layout design dependent factors influencing the DUT characteristics are identified which are 1) way of positioning of the on-wafer structures w.r.t. DUT (e.g. in line or checkerboard pattern) and 2) the spacing between on-wafer structures and the DUT. Afterwards, a guideline to reduce the influence of on-wafer neighbours on the DUT characteristics is presented. The optimization of the layout floorplan with minimal on-wafer neighbours prior to their fabrication also permits to reduce the costs with respect to occupied Si area.

This paper presents the preliminary measurement result of the wide-band radio frequency (RF) moisture sensor for oil and gas pipe thermal insulator. The thermal insulator with metal jacket such as fiberglass, mineral wool, rock wool, cellulose, polyurethane foam, polyurethane, etc. is employed around pipelines, piping and other equipment to control the temperature during transfer of substance. The corrosion under thermal insulator (CUI) due to salt water is the most dangerous problem when undetected. The indirect method for detecting CUI employs the thermal insulator moisture data. The advantages of the proposed wide-band RF moisture sensor are a wide detection rage compared to the conventional technique and high accuracy. The proposed system consists the voltage control oscillate (VCO) of 1.2 GHz to 2.7 GHz, the power detector, the microcontroller and transmitting (Tx) RF probe and receiving RF probe.

In this article, we present on-wafer thru-reflect-line (TRL)-calibrated measurements of silicon test structures fabricated using STMicroelectronics’ B55 technology up to 500 GHz. The structures are fabricated in two subsequent runs, and the respective structure in each run has a different design. The improvements in the test structures layout design are presented on the terminal capacitances of “open-M1,” which is an important test structure for the deembedding of the transistor accesses. The improvements are examined using high-frequency structure simulator (HFSS) electromagnetic (EM) simulations, including the RF probe models and the neighboring structures.

The paper reports investigation result of long-term stability for on-wafer measurement system adopting an automatic probing system developed by NMIJ-AIST. To RF probe coordinates in X-, Y-, Z-directions and tilt angle, their origins can automatically be adjusted by using actual measured S-parameter in the measurement system. The measurements were continued for 3 months to investigate on the stability by using same calibration and verification devices. A matched transmission line was used as the verification device. A standard deviation of measured refection coefficient achieved to approximately −50 dB, and that of measured transmission coefficient reached to approximately −60 dB. These deviation values are comparable to the short-term repeatability in measurement presented by other laboratory, even if the measurements are proceeded for long period, i.e. 3 months.

This paper details the design, fabrication, and testing of a new portable magnet, generically termed the Proteus magnet, that can undertake a wide range of MR measurements. The Proteus magnet is intended for 1H measurements of liquids and is fully functional when submersed in the sample of interest. The Proteus magnet is fabricated from a pair of low-cost, commercial, NdFeB disk magnets, axially polarized, with their North and South poles aligned. The two N52 NdFeB magnets – 31.75 mm diameter and 6.35 mm thickness were separated by 10 mm. The gap between the magnets is sufficient for a RF shield and transverse rectangular solenoid RF probe. The sensor was evaluated through a series of measurements including bulk CPMG, saturation recovery T1, self-diffusion, T1 – T2, and D – T2.

As a core component of the NMR two-phase flow probe, the RF coil plays an important role in signal transmission and magnetic field excitation. The traditional solenoid coil reduces the uniformity of the magnetic field due to the end effect, which affects the measurement accuracy of the resonance signal. To solve this problem, a new type of winding structure with multi-stage dense combination is proposed. In this paper, the comsol simulation tool is used to numerically simulate the distribution characteristics and matching relationship between the static magnetic field and the RF field in the detection area, and optimize the design of the coil structure parameters under the constraints of the size of the tubing. The simulation and experimental results show that the optimized coil structure has high signal-to-noise ratio, and the magnetic field is stable and uniformity within the error tolerance range within ±20 cm of the axial distance of the sensor, which effectively solves the end effect. The problem of rapid magnetic field drop has important reference value for the design of NMR two-phase flow RF probe.

In this paper, surface acoustic wave (SAW) devices with various designs were fabricated on two types of piezoelectric substrates of LiNbO3 bulk material and thin piezoelectric ZnO film on silicon. Different sizes, orientation and types of SAW devices were laid out on the same mask to compare their RF performance with a same fabrication. Devices were fabricated using lift-off technology with a double photoresist technique to achieve a steeper and narrower SAW pattern with a depth-to-width ratio of 1.27 and a steep resist angle of 85°. The devices were then characterized using RF probe station together with vector network analyzer. RF performance was also verified by 2D computer simulation implementing both electrical and piezoelectric physics models using the same device dimensions in the mask layout. RF response of 128°Y LiNbO3 from experiments agrees with simulation fairly well while the devices on ZnO/Si have larger frequency distribution due to process variation of the ZnO thin film on silicon wafer. Quality factor of 34,000 was obtained from the SAW device fabricated in LiNO3 substrate and this Q value has a strong dependency on the numbers electrodes of IDT fingers and reflectors. Temperature dependency was also measured for future wireless sensor application. The temperature coefficient of frequency of 16 μm wavelength devices of LiNbO3 substrate was −87.5 ppm/°C and was −72.41 ppm/°C for 12 μm wavelength devices.

Objective The aim of this study was to evaluate the effect of bipolar radiofrequency (RF) energy on canine stifle joint fluid temperature. Materials and Methods A standard stifle arthroscopy was performed on 15 canine large breed cadaveric stifle joints. A bipolar RF (VAPR III, 2.3-mm side effect electrode; Depuy Mitek, Raynham, Massachusetts, United States) unit was activated in the joint (1) with or without direct tissue contact, (2) with or without additional 18-gauge needle outflow and (3) for 15 and 30 seconds. The joint fluid temperature was monitored with two fibre optic intra-articular sensors. Results The stifle joint fluid temperature was significantly higher when there was no contact between the tissue and RF probe (mean: 58.6°C with 95% confidence interval [CI]: 53.3–64.0°C) compared with when tissue was contacted (mean: 29.0°C with 95% CI: 26.3–31.6°C). An 18-gauge egress needle had minimal effect on reducing joint fluid temperature. The temperature was higher during the 30-second application of RF energy than the 15-second group. Clinical Significance Bipolar RF energy without firm tissue contact rapidly and significantly increased joint fluid temperature beyond the level reported to damage chondrocytes (above 45°C). Caution is required in the use of bipolar RF energy in the canine stifle joint.

In this study, a novel ratiometric fluorescent sensor for ultrasensitive and visual quantitative detection of Ag+ with naked eyes was rationally designed and synthesized by encapsulating formamide-derived N-doped carbon dots (FA-CDs) in the cavities of Eu(III)-based metal-organic frameworks (Eu-MOFs). Benefiting from the specific coordination interaction of C N groups with Ag+, the firstly synthesized FA-CDs could selectively sense Ag+ based on the turn-off mode with a low detection limit (LOD) of 0.5 nM. After embedding FA-CDs in Eu-MOFs, owing to the robust self-calibration function and excellent accumulation effect of Eu-MOFs, the developed FA-CDs@Eu-MOFs-based ratiometric fluorescence (RF) probe has a more prominent selectivity toward Ag+ with an ultrasensitive fluorescence response across a broad range of 0.3–100 nM and an ultralow LOD of 80 pM, which is the lowest LOD value recorded of all the reported CDs-based and MOFs-based Ag+ sensors. The fabricated RF probe was successfully applied for the quantitative determination of Ag+ in environment water samples and commercial antibacterial Ag+ solution. More importantly, a novel FA-CDs@Eu-MOFs-based RF hydrogel sensor was successfully fabricated for the visual quantitative detection of Ag+ in commercial antibacterial Ag+ solution with naked eyes, which can be easily conducted without fluorophotometer-based calibration and provides an effective route to facilitate the evolution of visual fluorescent sensors from qualitative/semi-quantitative to quantitative detection.

For the IFMIF/EVEDA accelerator prototype RFQ linac, a 175 MHz rf input coupler based on a 6 1/8 in. co-axial waveguide is designed and manufactured. The rf coupler has cooling channels into the loop antenna and inner/outer-conductors around the RF window for CW operation mode, and the rf vacuum window module is replaceable by flanged connection. For rf power capability, nominal rf power of 160 kW and maximum transmitted rf power of 200 kW are required. In order to test the rf power capability, rf power tests using a high-voltage standing waves on a high-Q load circuit are carried out. For manufactured nine rf couplers including one spare, a stable 14 s CW operation at the equivalent rf power of 200 kW were achieved within 3–5 days rf aging. No rf contact defects, no unnecessary low-Q value and no extraordinary outgassing were validated.

Microwave wireless power transmission (MWPT) is a promising technique for low and medium power applications such as wireless charging for sensor network or for biomedical chips in case with long ranges or in dispersive media such. A key factor of the MWPT technique is its efficiency, which includes the wireless power transmission efficiency and the radio frequency (RF) to direct current (DC) voltage efficiency of RF–DC converter (which transforms RF energy to DC supply voltage). The main problem in designing an RF–DC converter is the nonlinear characteristic of Schottky diodes; this characteristic causes low efficiency, higher harmonics frequency and a change in the input impedance value when the RF input power changes. In this paper, rather than using harmonic termination techniques of class E or class F power amplifiers, which are usually used to improve the efficiency of RF-DC converters, we propose a new method called “optimal input impedance” to enhance the performance of our design. The results of simulations and measurements are presented in this paper along with a discussion of our design concerning its practical applications.

The evaluation of dielectric properties in the radio frequency (RF) bandwidth is highly relevant to characterize the physical or physiological state of organic materials. This paper reports on the implementation of an easy-to-use and contactless RF dielectric sensing technique used for the monitoring of the heat-induced gelation of a white egg sample. The sensing technique basically consists in the distant monitoring of a high-quality factor inductive RF resonator operating at 98 MHz, which is electromagnetically coupled to the egg white sample. A lumped element modeling of the contactless RF probe interacting with the egg white is proposed. It is used to estimate both the conductivity and the permittivity of the sample during its gelation, starting from the impedance changes measured at the ends of the RF probe, and after probe calibration carried out using a reference NaCl solution. The results obtained during a 10 h monitoring experience allow the dynamics of the egg white gelation to be analyzed. These results open the way to the development of easy-to-implement and non-invasive dielectric monitoring of organic materials, with many prospects in agrifood as well as health monitoring applications.

This paper presents a systematic design methodology for impedance matching circuits of an RF energy harvester to maximize the harvested energy for a range of input power levels with known distribution. Design of input matching networks for RF rectifier differs from those for traditional RF circuits such as low-noise amplifier because the transistors in the RF rectifiers operate in different regions. In this work, it is shown that the input impedance of the rectifier estimated based on small signal simulation of transistors at the peak of input signal in the rectifier when the transistors are biased with stable DC operating voltage provides the largest harvested energy from a fixed input power. For variable input power levels, a matching network selection strategy is proposed to maximize expected harvested energy given the probability density distribution of input power levels. As an experimental sample, an RF energy harvester circuit is designed to maximize the harvested energy in the 902928MHz band employing an off-chip impedance matching circuit designed using the proposed methodology. The proposed RF energy harvester exhibits a measured maximum power conversion efficiency (PCE) of 32% at 15dBm (32W) and delivers an output DC voltage of 3.2V to a 1M load.

In the frequency dissemination system over fiber, users can obtain highly stable RF frequency signal from one frequency source. To ensure that the stability loss of the system meets the user's need, performance evaluation for RF frequency dissemination over fiber is necessary. Considering the numerous users over fiber links and the long dissemination distance, traditional transfer quality evaluation method is not very practical, because the cost of the loop-back configuration is relatively large. In this paper, we propose a method to directly evaluate the radio frequency transfer quality via fiber links at the remote site. At the local site, the radio frequency signal is amplitude-modulated on continuous-wave lasers with two wavelengths. After multiplexing, the frequency signal is disseminated to the remote site. At the remote site, RF signal is detected from the continuous-wave optical carrier and transfer performance can be evaluated by measuring the phase fluctuation difference between two different RF signals. The remote signal does not need to be sent back to the local site. It will greatly simplify the structure of the frequency dissemination link, like in an antenna array system.

In this paper, a new method of designing RF ring oscillator using current-mode technology is presented. The current-mode low frequency oscillator theory is transferred to facilitate the design of RF ring oscillator. As an example, a current-mode RF quadrature ring oscillator (RFQRO) for $L$ -band wireless communication applications is presented. The current-mode RFQRO consists of two first-order all-pass filters, and it provides four quadrature RF sinusoidal outputs. The proposed current-mode RFQRO is verified with GlobalFoundries’ $0.18~\mu \text{m}$ 1P6M CMOS RF process. The simulated and measured results demonstrate that the proposed RFQRO works at 1.03 GHz, and its frequency tuning range is from 648.9 MHz to 1.17 GHz by adjusting the bias voltage from 0.62 to 1 V. The measured phase noise of the RFQRO is −105.5 dBc/Hz at 1 MHz offset, and it consumes 2.5 mW from 1 V supply voltage.

WOS: 000417961300025 Despite their reliability, on-site measurements are time-consuming and costly actions for the evaluation of new devices. Channel emulators are widely utilized measurement instruments to generate desired environmental channel effects in laboratory environments. Within these instruments, baseband emulators are expensive, and reverberation chambers provide limited control of the channel. However, radio-frequency (RF) circuit implementation of channel emulators provides an affordable and easy tool to test performances of new systems and methods under different channel effects. In this paper, a new RF domain Doppler emulator, which is compact and easy to control, is presented for measuring signal characteristics under frequency dispersive channel conditions. The circuit has been implemented using variable attenuators, switches, and power splitters to emulate the Doppler spread of air-ground channels, and the performance is evaluated through measurements. It is observed that the emulator indeed generates the desired Doppler model close enough to replicate environmental channels for mobile applications in laboratory environments. Savronik [SV.SOZ.E/0043.14.008] This work was supported by Savronik under Project SV.SOZ.E/0043.14.008'. The Associate Editor coordinating the review process was Dr. Huang-Chen Lee. (Corresponding author: Murat Karabacak.)

In the test of most devices in the radio frequency field, we need to know the value of current/voltage of a certain part on PCB, making sure it won’t show nonlinearity. Aiming at the difficulties of current/voltage measurements in the RF, this paper designs a new scheme of Rogowski coil called current loop, creating a high transmission impedance and small insertion loss by designing an overlapping structure, and the experiment proves good consistency with the simulation results. The design also produces the relevant printed circuit boards to improve the accuracy of the experiment, which include two parts: extraction of the plate parameters(DK and DF), and de-embedding of two ports to improve the feasibility of the experiment. The proposed methods play an important role in the challenges of EMC and SI.

Photonic Doppler frequency shift (DFS) measurement based on an integrated silicon photonic chip, which contains two cascaded dual-drive-Mach-Zehnder modulators (DDMZMs) and a photodetector (PD), is proposed and experimentally demonstrated. The reference signal is applied to the first DDMZM, while the transmission signal and the echo signal are injected into the second DDMZM through a differential RF probe. The optical carrier modulated by the three microwave signals is sent to a PD to achieve optical-to-electrical conversion. The DFS generated by the frequency beating between the transmission signal and echo signal, and two additional frequency components produced by the frequency beating between the transmission/echo signal and the reference signal are obtained. The target moving direction can thereby be identified by comparing the frequency locations of these three beat signals. A proof-of-concept experiment is carried out. The DFS from -100 to 100 kHz is estimated for a microwave signal at 10 GHz with an error of less than 1 Hz.

This paper presents a high-resolution magnetic field mapping system in development that is capable of collecting spatial magnetic field data for NMR magnets. An NMR probe was designed and built with a resonant frequency of 5.73 MHz. The measured Q-factor of the NMR probe is ∼191 with a half-power bandwidth in the range of 5.72–5.75 MHz. An RF continuous-wave technique with magnetic field modulation was utilized to detect the power dispersion of water molecules. The zero-crossing frequency of the NMR dispersion signal corresponds to the magnetic field at the center of the water sample. An embedded system was developed to sweep the frequency and record the reflected RF power simultaneously. A numerically controlled digital oscillator is able to provide a precise frequency step as small as 0.02 Hz, which is equivalent to 4.7 e-7 mT for hydrogen atoms. An RF preamplifier was built to supply up to 4 W of RF power to a bidirectional coupler. The coupler supplies RF power to the NMR probe and channels reflect the RF power back to the detection circuit, which detects the reflected RF power from the NMR probe during the frequency sweep. The homogeneity of an NMR magnet can be determined by magnetic field data.

In this paper, a contactless radio-frequency (RF) inductive probe is used to spatially localize and characterize a complex dielectric organic inclusion in a fluid. The effect of dielectric properties (DP) of this organic material is investigated experimentally and by numerical computations.The used RF probe is a 135 MHz 3 cm diameter and 10 cm long, cylindrical bracelet resonator, placed close to a water tank filled with deionized water which includes a 1.5 cm diameter inclusion filled of air or NaCl solutions and placed in arbitrary positions. The water tank and the inclusion are used to model an organic material including a tumor. The RF probe is used as a transmit and receive sensor. It induces a magnetic field inside the water tank, which, by reciprocity, conveys information about the DP of the investigated material. The impedance changes at the end of the RF probe are directly related to the modifications of the magnetic field, and are measured by means of a network analyzer. A complex fit of the impedance frequency response around the resonance frequency gives access to two quantities proportional to the electrical conductivity and dielectric constant of the inclusion. The inclusion is moved into the water tank along the three axes by means of a robotic arm, so that two three dimensional maps of the equivalent dielectric quantities in function of the inclusion position are sensed by the probe. Then, the inclusion is filled with different conductive NaCl solutions from 0.1 to 1.1 S/m in order to test the ability of the probe to sense the modifications of the dielectric properties of the inclusion. Experimental as well as computation results obtained using the Distributed Point Source Method (DPSM) validate the ability of the proposed probe to localize the inclusion as deep as 1 cm into the water, and the ability of the probe to sense the dielectric property changes of the inclusion.

Spastic Cerebral Palsy is the most common type of Cerebral Palsy (CP) that affects muscle coordination and control. Using Radiofrequency Ablation (RFA) to target the motor branches of the median and ulnar nerve may provide an additional treatment to Botulinum Toxin for spasticity in the hand. However, there are a limited number of studies that report the use of RFA in treating upper-limb spasticity. This prompts the need to establish a simulation model that has been tested against physical phantom to help determine the efficacy of RFA as a treatment for spasticity. In this study, a 3D COMSOL Multiphysics model of a commercial RF probe was validated against a Thermochromic Liquid Crystal (TLC) homogeneous gel phantom. The results of the COMSOL model were compared to the TLC phantom in terms of temperature (0.42 ± 1.06°C for the TLC high temperature range and -1.90 ± 0.88°C for the TLC low temperature range), lesion shape (14.5 ± 5.0%) and lesion size (0.18 ± 0.06 mm). These results show that COMSOL Multiphysics may be feasible as a tool to characterise RF lesions if the reported errors are accounted for. Further work is required to develop a more complex COMSOL model that incorporates different tissue aspects. However, this is a first step to establishing a validated COMSOL model of a RF probe in homogeneous muscle tissue.

The goal of thermal ablation is to destroy cancerous cells by increasing the temperature of the target tissue. Among the ablative techniques, radiofrequency (RF) ablation is the most widespread since it can be used in both percutaneous and surgical settings, in safety and with relative ease of use. However, efforts to optimize the RF treatment are needed, considering that the size of necrotized lesions remains a central issue in the application of the ablative procedure. In this work we aimed to evaluate the temperature distribution around the RF probe during radiofrequency ablation (RFA) of ex-vivo animal livers. Temperature maps in the ablated area are obtained by equipping a commercial RF probe with 27 Fiber Bragg Grating sensors (FBGs). The experiments demonstrate the ability of the proposed setup to conduct multi-point measurements in tissues undergoing RFA and the dependence of temperature and thermal damage on insertion depth of the RF probe.

Radiofrequency (RF) ablation therapy is of great interest in cancer therapy as it is non-ionizing radiation and can effectively penetrate into the tissue. However, the current RF ablation technique is invasive that requires RF probe insertion into the tissue and generates a non-specific heating. Recently, RF-responsive nanomaterials such as gold nanoparticles (AuNPs) and iron oxide nanoparticles (IONPs) have led to tremendous progress in this area. They have been found to be able to absorb the RF field and induce a localized heating within the target, thereby affording a non-invasive and tumor-specific RF ablation strategy. In the present study, for the first time, we used a hybrid core-shell nanostructure comprising IONPs as the core and AuNPs as the shell (IO@Au) for targeted RF ablation therapy. Due to the magnetic core, the nanohybrid can be directed toward the tumor through a magnet. Moreover, IONPs enable the nanohybrid to be used as a magnetic resonance imaging (MRI) contrast agent. In vitro cytotoxicity experiment showed that the combination of IO@Au and 13.56-MHz RF field significantly reduced the viability of cancer cells. Next, during an in vivo experiment, we demonstrated that magnetically targeting of IO@Au to the tumor and subsequent RF exposure dramatically suppressed the tumor growth. Therefore, the integration of targeting, imaging, and therapeutic performances into IO@Au nanohybrid could afford the promise to improve the effectiveness of RF ablation therapy.

Background and objectives: Recently, there have been calls for RFA to be implemented in the bipolar mode for cancer treatment due to the benefits it offers over the monopolar mode. These include the ability to prevent skin burns at the grounding pad and to avoid tumour track seeding. The usage of bipolar RFA in clinical practice remains uncommon however, as not many research studies have been carried out on bipolar RFA. As such, there is still uncertainty in understanding the effects of the different RF probe configurations on the treatment outcome of RFA. This paper demonstrates that the electrode lengths have a strong influence on the mechanics of bipolar RFA. The information obtained here may lead to further optimization of the system for subsequent uses in the hospitals. Methods: A 2D model in the axisymmetric coordinates was developed to simulate the electro-thermophysiological responses of the tissue during a single probe bipolar RFA. Two different probe configurations were considered, namely the configuration where the active electrode is longer than the ground and the configuration where the ground electrode is longer than the active. The mathematical model was first verified with an existing experimental study found in the literature. Results: Results from the simulations showed that heating is confined only to the region around the shorter electrode, regardless of whether the shorter electrode is the active or the ground. Consequently, thermal coagulation also occurs in the region surrounding the shorter electrode. This opened up the possibility for a better customized treatment through the development of RF probes with adjustable electrode lengths. Conclusions: The electrode length was found to play a significant role on the outcome of single probe bipolar RFA. In particular, the length of the shorter electrode becomes the limiting factor that influences the mechanics of single probe bipolar RFA. Results from this study can be used to further develop and optimize bipolar RFA as an effective and reliable cancer treatment technique.

Multiple frequency heating has been used since the '90 in ECR ion sources as heating schemes able to improve current intensities especially for highly charged ions. More recently, "Two Close Frequency Heating", where the frequency gap is comparable with the scale-length of the resonance, has been proposed, expected also to be sensitive to the relative waves phase relationship. At ATOMKI - Debrecen a dedicated experiment has been carried out for exploring the effects of the combined frequencies and their relative phase-difference in an argon plasma. The second frequency was finely tuned between 13.6-14.6 GHz with respect to the first one (fixed 14.25 GHz). An optimal frequency gap (in terms of Ar¹¹⁺/A⁶⁺ beam currents ratios) has been experimentally found, in agreement with the theory; the optimal power balance (total RF power was 200 W) between the two frequencies has been determined empirically. A weak but clear effect of the relative phase shift has been observed. Each configuration has been characterized by a multi-diagnostics set-up: HPGe and SDD detectors were used for the X-rays, a RF probe was introduced inside the plasma chamber to detect the radio-emission from the plasma., Proceedings of the 23th Int. Workshop on ECR Ion Sources, ECRIS2018, Catania, Italy

Phosphate plays an important role in a wide range of chemical and biological processes, so the development of a new phosphate optical sensor with high sensitivity, specificity and visual recognition function has important practical significance. Herein, a ratiometric fluorescent (RF) probe and a smartphone-integrated colorimetric test paper sensing platform for assay phosphate was fabricated using hybrid fluorescent UiO-66-NH2 and Eu3+@MOF-808 metal−organic frameworks. After continuous addition of phosphate, the blue fluorescence emission of UiO-66-NH2 and the red emission of Eu3+@MOF-808 were regularly enhanced and quenched respectively, and the fluorescence response of the detection platform to phosphate exhibited a clear color change process (red → pink → blue). More importantly, the probe solution and test paper of the integrated smartphone are converted to digital values through RGB channels and successfully used to visualize semi-quantitative recognition of phosphate. In addition, an RF probe and a smartphone integrated fluorescent test paper were developed separately to devise logic gate devices for detecting phosphate. The multifunctional ratio sensing platform integrated by the smartphone furnishes a new strategy and broad prospects for the intelligent online identification of important targets in biological samples and environmental samples.

A new parallel-plate resonator for 7Li ion cell studies is introduced along with a removable cartridge-like electrochemical cell for lithium ion battery studies. This geometry separates the RF probe from the electrochemical cell permitting charge/discharge of the cell outside the magnet and introduces the possibility of multiplexing samples under test. The new cell has a geometry that is similar to that of a real battery, unlike the majority of cells employed for MR/MRI studies to this point. The cell, with electrodes parallel to the B1 magnetic field of the probe, avoids RF attenuation during excitation/reception. The cell and RF probe dramatically increase the sample volume compared to traditional MR compatible battery designs. Ex situ and in situ 1D 7Li profiles of Li ions in the electrolyte solution of a cartridge-like cell were acquired, with a nominal resolution of 35 µm at 38 MHz. The cell and RF probe may be employed for spectroscopy, imaging and relaxation studies. We also report the results of a T1-T2 relaxation correlation experiment on both a pristine and fully charged cell. This study represents the first T1-T2 relaxation correlation experiment performed in a Li ion cell. The T1-T2 correlation maps suggest lithium intercalated into graphite is detected by this methodology in addition to other Li species.