Continuous Wave RF Research Articles

High Q and high gradient performance of the first medium-temperature baking 1.3 GHz cryomodule

The world’s first 1.3 GHz cryomodule containing eight 9-cell superconducting radio-frequency (rf) cavities treated by medium-temperature furnace baking (mid-T bake) was developed at the Institute of High Energy Physics, Chinese Academy of Sciences. The 9-cell cavities in the cryomodule achieved an unprecedented high average intrinsic quality factor (Q0) of 3.8×1010 at 16 MV/m and 3.6×1010 at 21 MV/m in the horizontal test. The cryomodule can operate stably up to a total continuous wave rf voltage greater than 193 MV, with an average cavity usable accelerating gradient of more than 23 MV/m. The results significantly exceed the specifications of Circular Electron Positron Collider and Dalian advanced light source and the other high repetition rate free electron laser facilities [Linac Coherent Light Source II (LCLS-II), LCLS-II-high energy, Shanghai High Repetition Rate X-ray FEL and Extreme Light Facility, Shenzhen Superconducting Soft X-Ray Free Electron Laser, etc.]. There is evidence that the mid-T bake cavity may not require fast cooldown or long processing time in the cryomodule. This paper reviews the cryomodule performance and discusses some important issues in cryomodule assembly and testing. Published by the American Physical Society 2024

Structural and molecular alterations in murine tissue due to far-field radiofrequency exposure

Public concern over exposure to radiofrequency electromagnetic fields has prompted several studies to determine possible health outcomes. However, studies on low level far-field radiofrequency (RF) exposure remain inconclusive on whether it can alter biological systems. Our study's aim was to evaluate structural and molecular modifications such as apoptosis and gene expression in murine brain, liver and kidney tissues exposed to a far-field RF of 915 MHz at a whole-body specific absorption rate of 1.17 W/kg. Forty (40) Swiss male mice were equally and randomly divided into 2 groups: a control group and an RF-exposed group. Each were further equally subdivided (n=5 per subgroup) based on different time points: baseline or no exposure, 3-day exposure, 6-day-exposure and 9-day exposure subgroups. Biometric parameters such as body temperature, body weight, and organ weight were obtained. Tissue samples were collected and analyzed using light and electron microscopy, followed by qPCR assay for both the p53 and Hsp-70 genes. Statistical analysis was performed using ANOVA. There was evidence of both structural and molecular modification beginning Day 3 from continuous-wave far-field RF exposure. The study established multi-level alterations in the murine system due to far field RF exposure providing a glimpse of possible biological effects, and therefore, a need for further studies to translate such evidence in a larger biological perspective.

Combined ns pulsed-RF excitation and impedance matching considerations for the production of moderate E/n atmospheric pressure discharges for gas conversion

Sub-breakdown radiofrequency (RF) discharges enabled by a nanosecond (ns) pulse ignition source are studied at atmospheric pressure in a range of gas mixtures from completely inert (in Ar) to completely reactive (in CO2). An electrical characterisation of the continuous wave (CW) RF discharge (13.56 MHz) is performed to determine plasma impedance and plasma power dissipation. Two different measurement methods to electrically characterize the system are described and compared. One method uses in-situ measurements of discharge parameters (voltage, current and the phase angle), and the other method performs ex-situ measurements of the load circuit using a vector network analyser. It was found that RF plasma power deposition depended on the applied RF power as well as the gas mixture composition. Using the in-situ voltage, current and phase angle measurements, plasma power deposition was calculated to be as much as 85% and 76% of the applied RF power for the pure Ar and pure CO2 cases, respectively. A preliminary qualitative assessment of the plasma composition was performed by optical emission spectroscopy, and CO2 conversion by mass spectrometry. CO2 to CO conversions of 11.2% and 5.5% in a 20:80 (CO2:Ar) mixture and in 100% CO2, respectively, were observed. This study demonstrates a RF plasma source for gas conversion applications at atmospheric pressure in a completely reactive gas.

Vector-based feedback of continuous wave radiofrequency compression cavity for ultrafast electron diffraction.

The temporal resolution of ultrafast electron diffraction at weakly relativistic beam energies (100 keV) suffers from space-charge induced electron pulse broadening. We describe the implementation of a radio frequency (RF) cavity operating in the continuous wave regime to compress high repetition rate electron bunches from a 40.4 kV DC photoinjector for ultrafast electron diffraction applications. Active stabilization of the RF amplitude and phase through a feedback loop based on the demodulated in-phase and quadrature components of the RF signal is demonstrated. This scheme yields 144 ± 19 fs RMS temporal resolution in pump-probe studies.

RF conditioning towards continuous wave of the RFQ of the Linear IFMIF Prototype Accelerator

The Linear IFMIF Prototype Accelerator (LIPAc) is designed to accelerate 125mA of deuteron beam to 9MeV in continuous wave (CW). The superconductive RF Linac has not yet been installed and the final accelerating stage now under commissioning is the RFQ. This system has been designed and developed by INFN (Italy) before installation in QST (Japan). The RFQ is the longest in the World with its 9.8m and requires RF power injection from 8 independent and synchronized coupler ports. LIPAc demonstrated the acceleration of 125mA deuteron beam at 5MeV for 1ms with a 1s repetition period in 2019. A fundamental milestone to extend beam operations to CW is the completion of the RFQ cavity RF conditioning up to CW. This work presents the strategy followed to successfully reach CW RF injection at 80% of the nominal 132kV vane voltage. The field distribution correction scheme (acting on cooling system at various power levels) was successfully verified. We discuss as well the main challenges encountered on the way, which include updates of the RF system, failure of a circulator (by arcs) and the damages occurred on some of the RF couplers. Finally, the recent status and outlook will be provided.

Resonant Radar Reflector On VHF / UHF Band Based on BPSK Modulation at LEO Orbit by MRC-100 Satellite

This paper presents a novel method for identify ing and tracking PocketQube satellites: the MRC-100 satellite is a model, and this method is based on a resonant radar reflec tor. The resonant reflector’s basic concept is that the resonant reflector uses a VHF/UHF communication subsystem antenna; there is no radiated RF signal, which means the power con sumption is only some Milliampere (mA). The continuous wave (CW) illuminator RF source is on the ground, and the onboard antenna receives the CW RF signal from the Earth. The micro controller (uC) periodically switches PIN diode forming BPSK modulated signal reflection so that another Earth station can receive the backscattered Binary Phase Shift Keying (BPSK) modulated signal. Also, it can detect the satellite if the ground station receiver can use a matched filter like a correlation re ceiver. If the ground station receiver knows the BPSK code of the satellite, it can detect it. If not, there is no way to detect the satellite. This method is similar to Radio Frequency Identifica tion (RFID) applications, but the reader is the ground station, and the tag is the satellite.

Fast and robust pulsed chemical exchange saturation transfer (CEST) MRI using a quasi-steady-state (QUASS) algorithm at 3 T

Chemical exchange saturation transfer (CEST) has emerged as a powerful technique to image dilute labile protons. However, its measurement depends on the RF saturation duration (Tsat) and relaxation delay (Trec). Although the recently developed quasi-steady-state (QUASS) solution can reconstruct equilibrium CEST effects under continuous-wave RF saturation, it does not apply to pulsed-CEST MRI on clinical scanners with restricted hardware or specific absorption rate limits. This study proposed a QUASS algorithm for pulsed-CEST MRI and evaluated its performance in muscle CEST measurement. An approximated expression of a steady-state pulsed-CEST signal was incorporated in the off-resonance spin-lock model, from which the QUASS pulsed-CEST effect was derived. Numerical simulation, creatine phantom, and healthy volunteer scans were conducted at 3 T. The CEST effect was quantified with asymmetry analysis in the simulation and phantom experiments. CEST effects of creatine, amide proton transfer, phosphocreatine, and combined magnetization transfer and nuclear Overhauser effects were isolated from a multi-pool Lorentzian model in muscles. Apparent and QUASS CEST measurements were compared under different Tsat/Trec and duty cycles. Paired Student's t-test was employed with P < 0.05 as statistically significant. The simulation, phantom, and human studies showed the strong impact of Tsat/Trec on apparent CEST measurements, which were significantly smaller than the corresponding QUASS CEST measures, especially under short Tsat/Trec times. In comparison, the QUASS algorithm mitigates such impact and enables accurate CEST measurements under short Tsat/Trec times. In conclusion, the QUASS algorithm can accelerate robust pulsed-CEST MRI, promising the efficient detection and evaluation of muscle diseases in clinical settings.

Physical design and multi-physics analysis of a 200 MHz continuous wave radio frequency quadrupole accelerator for a proton accelerator facility

Based on the platform of a proton accelerator facility, a 200 MHz high intensity continuous wave (CW) radio frequency quadrupole (RFQ) accelerator has been designed at the Sino-French Institute of Nuclear Engineering and Technology of Sun Yat-Sen University, China. Employing the conventional four-vane structure, the RFQ can accelerate 20 mA proton beam from 20 keV to 2.5 MeV. In the beam dynamics design, the simulated transmission efficiency reaches 99.5% and the vane length is less than 4 m. In the electromagnetic design, for the long-term stable operation, Pi-mode Stabilizer Loops (PISLs) are utilized to achieve more than 10 MHz mode frequency separation and to decrease the effects of dipole modes. The 48 tuners are optimized to provide a range of ± 2 MHz frequency tuning. Additionally, the undercuts are optimized to ensure a good field flatness along the longitudinal direction. Based on the coolant channel design, the multi-physics analysis is performed to investigate the deformation and stress resulting from the dissipation of RF power within the cavity, as well as determine the temperature tuning coefficients of the coolants within the vane and wall. The entire design and analysis of PAFA-RFQ has been completed, and the scheme of the design can also be applied to the design of other RFQ cavities.

Changes in the histopathology and in the proteins related to the MAPK pathway in the brains of rats exposed to pre and postnatal radiofrequency radiation over four generations

The development of new technologies and industry increases the number and variety of electromagnetic field (EMF) sources. Researcher are increasingly interested in the effects of EMF on brain health. The brain's function is largely dependent on electrical excitability, so it would be expected to be vulnerable to EMF. We therefore investigated the effects of brain development in the fetus, histopathological changes in female rats and the hippocampal level of MAPK proteins in male rats after exposed to pre and postnatal 2450 MHz continuous wave (CW) radiofrequency radiation (RFR) over four generations. Four groups; sham, irradiated female, irradiated male, irradiated male and female, with each consisting of four rats (one male and three females) were created. Rats in the exposure groups were whole-body exposed to 2450 MHz CW-RFR for 12 h/day during the experiment. Irradiation started one month before fertilization in the experimental group. On the 18th day of the gestational period, one pregnant rat from each group was decapitated under general anesthesia and the fetuses were taken. The remaining two pregnant rats completed the normal gestation period. When the offspring were two months old, four rats, one male and three female, were allocated for the second generation study. Next generation animals were also experienced the same processes as the first generation rats. This study were evaluated development of brain in fetuses and histopathological changes in brain of female rats using haematoxylin eosin staining, and the hippocampal level of MAPK proteins in brain of male rats by Western Bloting. We observed hemorrhagic areas, irregular cellular localization and vascular structures in the brain of fetal and adult female rat of exposed groups in the all generations. pERK, ptau, pJNK and pP38 were increased in the brain of adult male rat of exposed groups in the all generations (p < 0.005). Pre and postnatal 2450 MHz continuous wave radiofrequency radiation exposure may cause changes in the function of the MAPK pathway affecting cognitive processes such as learning and memory and may cause damage to both the fetus and adult brain tissue. Also, EMF may have potential to affect brain of future generations.

Investigating the impact of RF saturation-pulse parameters on compartment-selective gas-phase depolarization with xenon polarization transfer contrast MRI.

To demonstrate the utility of continuous-wave (CW) saturation pulses in xenon-polarization transfer contrast (XTC) MRI and MRS, to investigate the selectivity of CW pulses applied to dissolved-phase resonances, and to develop a correction method for measurement biases from saturation of the nontargeted dissolved-phase compartment. Studies were performed in six healthy Sprague-Dawley rats over a series of end-exhale breath holds. Discrete saturation schemes included a series of 30 Gaussian pulses (8 ms FWHM), spaced 25 ms apart; CW saturation schemes included single block pulses, with variable flip angle and duration. In XTC imaging, saturation pulses were applied on both dissolved-phase resonance frequencies and off-resonance, to correct for other sources of signal loss and compromised selectivity. In spectroscopy experiments, saturation pulses were applied at a set of 19 frequencies spread out between 185 and 200 ppm to map out modified z-spectra. Both modified z-spectra and imaging results showed that CW RF pulses offer sufficient depolarization and improved selectivity for generating contrast between presaturation and postsaturation acquisitions. A comparison of results obtained using a variety of saturation parameters confirms that saturation pulses applied at higher powers exhibit increased cross-contamination between dissolved-phase resonances. Using CW RF saturation pulses in XTC contrast preparation, with the proposed correction method, offers a potentially more selective alternative to traditional discrete saturation. The suppression of the red blood cell contribution to the gas-phase depolarization opens the door to a novel way of quantifying exchange time between alveolar volume and hemoglobin.

Effects of pre and postnatal 2450 MHz continuous wave (CW) radiofrequency radiation on thymus: Four generation exposure

ABSTRACT This study aims to investigate the effects of pre- and postnatal 2450 MHz continuous wave (CW) radiofrequency radiation (RFR) on the thymus of rats spanning four generations. Four groups; sham, irradiated female, irradiated male, irradiated male and female, each consisting of four rats (one male and three females), were created. During the experiment, rats in the exposure groups were whole-body exposed to 2450 MHz CW-RFR for 12 h/day. Irradiation started one month before the fertilization in the experimental group. When the offspring were two months old, four rats, one male and three female, were allocated for the second-generation study. The remaining offspring were sacrificed under general anesthesia, and their thymuses were removed. The same procedure was applied to the next generation. Two months after the second generation gave birth, third-generation rats were decapitated, and their thymuses were removed. In all groups, cortex, medulla and resident cells could be clearly distinguished in the second and third generations. No differences were observed between the control and two experimental groups, defined as irradiated female and irradiated male. In contrast, vascularization was observed in the thymus of the fourth-generation offspring of the group where both males and females were irradiated. The number of offspring and mass of all rats decreased in the third-generation group. Pre-and postnatal 2450 MHz continuous wave radiofrequency radiation exposure may potentially affect the thymus of future generations.

Approach to calibrate actual cavity forward and reflected signals for continuous wave-operated cavities

Precise measurement of the cavity forward (Vf) and reflected signals (Vr) are crucial for calibrating other key parameters such as cavity detuning and forward power. In practice, the accuracy of these measurements is impacted by the crosstalk between the forward and reflected channels. For a pulsed radio-frequency (RF) system, DESY has proposed an algorithm to calibrate the actual Vf and Vr based on the cavity differential equation. This method requires the value of cavity voltage (Vc) changing over time to establish a complete differential equation. However, for a continuous wave (CW)-operated RF system, the signal Vc is almost constant over time thanks to the high gain feedback control of the low-level RF system. As a result, it is difficult to locate the optimal calibration factors using the DESY’s algorithm. Therefore, we offer an alternative algorithm to determine the calibration factors using the CW RF waveforms during a nominal RF shutdown event (RF power source is forced to shut down while the cavity remains working appropriately without any RF-related faults). The validity of the proposed algorithm was demonstrated on a Chinese ADS front-end demo superconducting linac (CAFe) facility that operated in CW mode. Using the calibrated Vf signal, we successfully estimated the beam current and beam phase during the CAFe beam commissioning, and we confirmed the accuracy of these estimations with the measurement result.

A Systematic Method to Explore Radio-Frequency Non-Thermal Effect on the Growth of Saccharomyces Cerevisiae

Radio frequency (RF) non-thermal (NT) bio-effects have been a subject of debate and attracted significant interests due to potential health risks or beneficial applications. In this work, we report a systematic method for broadband investigation of RF NT effects on <i>Saccharomyces cerevisiae</i> yeast growth. The method includes a transverse electro-magnetic (TEM) device and a dielectric spectroscopy technique for RF frequency selection. A stripline-based TEM device has two 240-<i>&#x03BC;</i>L chambers 3D printed for cell cultures. The fabricated device operates up to a few GHz and produces uniform RF fields for cell exposure testing. A vector network analyzer (VNA) was used to provide &#x2212;20 dBm continuous-wave (CW) RF power. The heating effects on cell growth were estimated to be negligible. Frequency regions, where large permittivity differences between the medium and yeast cultures were obtained and used to select RF testing frequencies, <i>e.g.,</i> 1.0 MHz, 3.162 MHz, 10 MHz. These differences may indicate RF field gradients near cell membrane, and the gradients may affect local nutrient transport. Additionally, RF at 905 MHz is tested for comparison purpose. Yeast cells in the exponential growth phase were examined at four RF frequencies and compared with two controls. One control device held at the same temperature as the test device, while the other control was held at a temperature 1 &#x00B0;C higher. The results showed that the RF fields at 3.162 MHz reduced yeast growth rates by 15.1&#x0025;; however, the RF fields at 1.0 MHz enhanced cell growth by 13.7&#x0025;, while the observed 4.3&#x0025; growth rate increase at 10 MHz is insignificant and the RF fields at 905 MHz had no effects on the cell growth. These results showed a clear RF NT effects on <i>S. cerevisiae</i> growth that was frequency dependent. The hypothesized mechanisms of these effects, i.e., non-uniform RF fields near cell membranes and fluidic diodes in cell membrane ion channels may play important roles in nutrient transport, need to be further investigated.

Wideband RF Transmit-Receive Switch for Multi-Nuclei NMR Spectrometers

The utility of wideband high field nuclear magnetic resonance (NMR) spectrometers is significant in many applications. Wideband radio frequency (RF) front-ends are critical for the realization of multi-nuclei spectrometers. To realize such systems, wideband Transmit-Receive (TR) switches and low noise amplifiers (LNA) should be implemented at the RF front-end (FE) of the system. Most of the common designs used nowadays on NMR spectrometers are either inherently narrowband and/or of relatively high noise-figure which limit the overall system performance to a large extent. To improve upon the conventional FE performance, a new design of wideband high-power TR switch which could be devised for multi-nuclei NMR spectrometers is introduced in this brief. The developed wideband TR switch employs PIN diode switching technique and a dual-driver circuit. A prototype was constructed and experimentally characterized. The small-signal measurement results show that the switch has a bandwidth from 30 – 200MHz where the return loss is maintained below 18 dB with insertion loss of 0.09 - 0.2dB in the transmit mode and 0.11 – 0.37dB in the receive mode. It also exhibits a very high isolation of 63 - 80dB over the entire bandwidth. It is demonstrated that the switch can withstand continuous-wave RF input with power levels as high as 125 W while maintaining low insertion loss and high isolation.

Development of high power 20 dB directional coupler for Ion Cyclotron Resonance frequency system of Tokamak

This article presents the design and fabrication of 20± 0.3dB directional coupler having 2kW power handling capability in the frequency range of 140-200MHz. The developed coupler has an important application in the prototype of the Ion Cyclotron Resonance Frequency (ICRF) system of Tokamak. The directional coupler used to couple the forward and reflected power for measurement and provide the feedback to the existing matching network responsible for protecting the high power RF source. The prototype ICRF system has been developed to test the matching speed of the ICRF system for load resilient operation. The developed coupler is compact in size, robust, and capable of handling 2kW, continuous wave (cw) RF power. This paper also analyses the dielectric breakdown strength using electric field distribution inside the coupler and the average power handling capability is determined using numerical analysis. The test and simulation results of developed coupler are found in good agreement. The test results using Vector Network Analyzer (VNA) are obtained as, the coupling flatness of 20 ± 0.3 in 140-200 MHz frequency range, return loss and isolation are -30dB and -35dB respectively. The work presented in this paper is helpful for the design and development of high power coupler in radio frequency (RF) range and may be applied in various applications such as RF Plasma, Radar, navigation, satellite and research etc.

Commissioning of the SLAC Linac Coherent Light Source II electron source

For the Linac Coherent Light Source II (LCLS-II) project at SLAC, a 1.3 GHz superconducting rf (SRF) linac is being constructed that will generate 4 GeV electron bunches at a high repetition rate to drive x-ray free electron lasers. The LCLS-II electron source, which comprises the first three meters of the electron injector, includes two normal-conducting, continuous-wave rf cavities: a one-cell, 185.7 MHz gun and a two-cell, 1.3 GHz buncher. It also includes a gun load-lock system that allows photocathodes to be changed under vacuum. The components in this beam-line section were designed and built by Lawrence Berkeley National Laboratory based on experience from their advanced photoinjector experiment program. In combination with the SLAC UV laser system, the electron source is designed to produce beam rates up to 1 MHz with average currents up to $30\text{ }\text{ }\ensuremath{\mu}\mathrm{A}$ initially. The source was installed in mid-2018, well in advance of the SRF linac, which is now nearing completion. The source was commissioned over a two-year period, and this paper presents results including electron beam and dark current characterization.

Effects of 1800 MHz radiofrequency fields on signal transduction and antioxidant proteins in human A172 glioblastoma cells

Purpose To assess the effects of 1800 MHz radiofrequency electromagnetic field (RF-EMF) exposure on the expression of signal transduction and antioxidant proteins in a human-derived A172 glioblastoma cell line. Materials and methods Adherent human-derived A172 glioblastoma cells (1.0 × 105 cells per 35 mm culture dish, containing 2 mL DMEM media) were exposed to 1800 MHz continuous-wave (CW) or GSM-modulated RF fields, in the presence or absence of serum for 5, 30 or 240 min at a specific absorption rate (SAR) of 0 (sham) or 2.0 W/kg. Concurrent negative (vehicle) and positive controls (1 µg/mL anisomycin) were included in each experiment. Cell lysates were collected immediately after exposure, stabilized by protease and phosphatase inhibitors in lysis buffer, then frozen and maintained at −80 °C until analysis. The relative expression levels of phosphorylated- and total-signal transduction proteins (CREB, JNK, NF-κB, ERK1/2, Akt, p70S6K, STAT3 and STAT5) and antioxidant proteins (SOD1, SOD2, CAT, TRX1, PRX2) were assessed using Milliplex magnetic bead array panels and a MagPix Multiplex imaging system. Results In cells exposed to 1800 MHz continuous-wave RF-EMF with the presence of serum in the culture medium, CAT expression was statistically significantly decreased after a 30 min exposure, total JNK was decreased at both 30 and 240 min of exposure, STAT3 was decreased after 240 min of exposure and phosphorylated-CREB expression was decreased after 30 min of exposure. In cells exposed to 1800 MHz GSM-modulated RF-EMF in serum-free cultures, the expression level of total STAT5 was decreased after 30 and 240 min of exposure. These observed changes were detected sporadically across time-points, culture conditions and RF-EMF exposure conditions indicating the likelihood of false positive events. When cells were treated with anisomycin for 15 min as a positive control, dramatic increases in the expression of phosphorylated signaling proteins were observed in both serum-starved and serum-fed A172 cells, with larger fold change increases in the serum-free cultures. No statistically significant differences in the expression levels of SOD1, SOD2 or TRX1 were observed under any tested conditions after exposure to RF-EMF. Conclusions The current study found no consistent evidence of changes in the expression of antioxidant proteins (SOD1, SOD2, CAT or TRX2) or a variety of signal transductions proteins (CREB, JNK, NF-κB, ERK1/2, Akt, p70S6K, STAT3, STAT5) in a human-derived glioblastoma A172 cell line in response to exposure to 1800 MHz continuous-wave or GSM-modulated RF-EMF for 5, 30 or 240 min in either serum-free or serum-containing cultures.

전자전용 S&amp;C 대역 GaN 반도체 고출력증폭기 설계 및 제작

This paper describes the design and measurement results of an S to C-band gallium-nitride (GaN) solid-state power amplifier (SSPA) for an electronic warfare jammer. The S to C-Band GaN SSPA is fabricated, without wideband isolator, with multiple combined of 80 W GaN module using wide-band impedance matching topology and Super CMC (S-CMC) carrier structure, and designed small-sized broadband matching circuit using a cascaded 90° hybrid coupler for improve impedance mismatching performance between GaN DRA and GaN HPA. The S to C-band GaN SSPA for the electronic warfare, with a continuous wave (CW) RF injection condition over a frequency range of 2 to 6.5 GHz, demonstrated performance with a saturated average output power of 225 W (330 W peak output power), 21.39 % power added efficiency (PAE). Furthermore, with 1 % duty &amp; 10 µs PW Pulse RF injection condition over an operation frequency range, it had performance with a saturated average output power of 287 W (404 W peak output power).

CRADLE: Combined RF/Acoustic Detection and Localization of Passive Tags

We introduce CRADLE, or combined RF/acoustic detection and localization, for the remote parametric ranging of passive tags. In this approach, a tag consists of an RF antenna connected to an ultrasonic transducer via a passive electrical network. A reader looks for tags by transmitting both continuous-wave RF and pulsed ultrasound into a region of interest; when a tag is within that region, the ultrasound incident on the tag transducer varies the transducer capacitance, creating a time-varying load for the tag antenna and thus parametrically modulating the RF waves reradiated from the tag. The reader localizes the tag by demodulating the received signal to recover the acoustic time of flight. In this paper, we present a proof-of-concept CRADLE system, describing the design of a custom tag and reader. The results of our localization experiments show that we can achieve sub-decimeter accuracy at reader-tag distances of up to 6 m using the proposed system; future improvements in the design of the tag and reader can result in localization of centimeter-sized tags with sub-centimeter accuracy out to distances of several meters.

RF performance evaluation of p-type NiO-pocket based β-Ga2O3/black phosphorous heterostructure MOSFET

The radio-frequency (RF) performance of the p-type NiO-pocket based β-Ga2O3/black phosphorous heterostructure MOSFET has been evaluated. The key figure of merits (FOMs) for device performance evaluation include the transconductance (g m) gate dependent intrinsic-capacitances (C gd and C gs), cutoff frequency (f T), gain bandwidth (GBW) product and output-conductance (g d). Similarly, power-gain (G p), power added efficiency (PAE), and output power (P OUT) are also investigated for large-signal continuous-wave (CW) RF performance evaluation. The motive behind the study is to improve the β-Ga2O3 MOS device performance along with a reduction in power losses and device associated leakages. To show the applicability of the designed device in RF applications, its RF FOMs are analyzed. With the outline characteristics of the ultrathin black phosphorous layer below the β-Ga2O3 channel region, the proposed device results in 1.09 times improvement in f T, with 0.7 times lower C gs, and 3.27 dB improved G P in comparison to the NiO-GO MOSFET. The results indicate that the designed NiO-GO/BP MOSFET has better RF performance with improved power gain and low leakages.