High Frequency Operation Research Articles

Intelligentization of wheel loader shoveling system based on multi-source data acquisition

To effectively reduce the operation intensity of drivers, it is essential to research the intelligent operation for various stages of loaders. The traditional operation mode of the loader requires the driver to manually complete the high repeatability and frequency operation of various stages, which makes the energy-saving characteristics of the loader particularly affected by the driver. Hence, this paper proposes intelligent operation methods for various stages of loaders based on the extraction and analysis of multi-sourced data characteristics of the experiment. Specifically, the automatic adjustment of the working device attitude in the shoveling stage is achieved. During the loading and unloading stages, the working device can be automatically lifted to the memorized angle, and the bucket can also be automatically leveled. The intelligent operation method solves the problem that the loader requires the driver to work with high intensity for various stages and improves the economic aspects.

Trends and Applications of Surface and Bulk Acoustic Wave Devices: A Review.

The past few decades have witnessed the ultra-fast development of wireless telecommunication systems, such as mobile communication, global positioning, and data transmission systems. In these applications, radio frequency (RF) acoustic devices, such as bulk acoustic waves (BAW) and surface acoustic waves (SAW) devices, play an important role. As the integration technology of BAW and SAW devices is becoming more mature day by day, their application in the physical and biochemical sensing and actuating fields has also gradually expanded. This has led to a profusion of associated literature, and this article particularly aims to help young professionals and students obtain a comprehensive overview of such acoustic technologies. In this perspective, we report and discuss the key basic principles of SAW and BAW devices and their typical geometries and electrical characterization methodology. Regarding BAW devices, we give particular attention to film bulk acoustic resonators (FBARs), due to their advantages in terms of high frequency operation and integrability. Examples illustrating their application as RF filters, physical sensors and actuators, and biochemical sensors are presented. We then discuss recent promising studies that pave the way for the exploitation of these elastic wave devices for new applications that fit into current challenges, especially in quantum acoustics (single-electron probe/control and coherent coupling between magnons and phonons) or in other fields.

Quantitative assessment and suppression of anharmonic potential of quadrupole linear radiofrequency ion traps with round electrodes

Precision manipulation of the quantum coherence of radiofrequency (RF) ion trap systems is one of the most important prerequisites for the development of high-performance ion frequency standards, high-fidelity ion trap quantum computing, and ion precision spectroscopy. The anharmonic potential of the ion trap exacerbates the non-ideal kinetic properties of the trapped ions and the simple harmonic motions of the heated ions, which in turn constrain the coherence time of the trapped ion systems. In this study, we developed a precision assessment and optimization method for the potential field of a quadrupole linear RF ion trap with round electrodes based on the joint weight suppression of the multi-order anharmonic potential, which is applicable for ion ensembles of cloud, liquid, and crystalline forms, and for different ion numbers. By quantifying the potential of each radial order of the decoupled transient RF potential, we established the quantitative loss relationship between the structure parameter of the linear RF ion trap with round electrodes and the trapping potential and outlined the influence of the structure parameter of the trap on the weight of the anharmonic potential. We determined the optimal structure parameter k (the ratio of pole radius re to radius r0 of the maximum trapping field) of the quadrupole linear ion trap with round electrodes as 1.1451447, which minimizes the overall anharmonic potential and achieves the highest reported accuracy (Reuben et al., 1996) [1]. This result provides a basis for the solution of problems in physics such as obtaining long-time trapping under low heating rate, precision manipulation of coherence, motion effect suppression, and efficient cooling of 3D ion systems, which are conducive to quantum coherence with time delays, spectral measurement approaching the theoretical accuracy limit, and high-performance frequency standards of 3D ion systems.

High-stability flexible radio frequency transistor and mixer based on ultrathin indium tin oxide channel

In this work, a high-performance flexible radio frequency transistor using an ultrathin indium tin oxide film channel based on a solution-cast thin polyimide substrate has been demonstrated. The 60 nm short channel transistor shows a record high cut-off frequency of 5 GHz and a maximum oscillation frequency of 11 GHz with high uniformity among 40 devices. The radio frequency characteristics under various bending conditions have been systematically studied under a bending radius of 5 mm for 10 000 times and a bending radius of 1 mm for 1000 times, showing excellent stability with only 20% decrease in the cut-off frequency. Furthermore, a flexible frequency mixer has also been demonstrated at 2.4 GHz with decent conversion gains.

A Harmonic-Mixing PLL Architecture for Millimeter-Wave Application

A low-noise synthesizer design in the millimeter-wave (mm-wave) range is complicated by the invariably large closed-loop gain and the high operation frequency of the voltage-controlled oscillator (VCO). To overcome these challenges, this work proposes a harmonic-mixing synthesizer system with a 188-dB figure-of-merit mm-wave VCO. The synthesizer extends the bandwidth to 5 MHz, thereby suppressing VCO noise. Importantly, DSM is not amplified by the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{\mathrm{ VCO}}/f_{\mathrm{ ref}}$ </tex-math></inline-formula> gain of the system. A prototype employing a 74-MHz reference achieves a −250-dB phase-locked loop (PLL) figure of merit with a measured 88-fs rms jitter.

Study on EMI suppression of a high–low voltage DC/DC converter in electric vehicle by periodic frequency modulation

The high–low voltage DC/DC converter of electric vehicle produces high du∕dt and di∕dt due to the high operating frequency of the power devices, which introduce nonnegligible electromagnetic interference. In this paper, the power devices control signals of the high–low voltage DC/DC converter were modulated by periodic signals, the influence of the modulation frequency, the maximum frequency deviation and the modulation waveform on the conducted electromagnetic interference were analyzed. Combined with the published data of the phase-shifted full-bridge circuit of the high–low voltage DC/DC converter, the spread-spectrum modulation control signal model and power circuit model were established in MATLAB/Simulink and PSIM, and co-simulations were carried out with different modulation parameters. The interference suppression effects of three test frequency bands required by CISPR 25 were tested; the optimal parameters for the periodic frequency modulation of the high–low voltage DC/DC converter in electric vehicle were proposed.

Wire gauge analysis of planar spiral coil and its optimization technique in Wireless Power Transfer system

Planar spiral coil made of solid wire is widely used in wireless power transfer without magnetic core in high frequency operation system. Based on the magnetic field distribution of planar spiral coil and high frequency eddy current loss mechanism, the influence of magnetic field strength, frequency, and wire gauge on the AC resistance of winding are analysed. It reveals that the coil loss can be reduced by designing the wire gauge. Then the magnetic field strength and the winding loss calculation model are built, based on which the double wire gauge for segmental winding structure is proposed. This method can reduce the AC resistance and improve the quality factor on the premise of keeping inductance constant at high frequency. Through simulation and experiment, the AC resistance of coil based on the double wire gauge scheme can be greatly reduced comparing to the traditional method and the efficiency of the prototype is increased by 4%, which verifies the theory analysis to be correct and flexible.

Design of a metal-based deformable mirror for orthogonal beam deflection and highly dynamic beam oscillation.

We report on an opto-mechanical metal mirror design for highly dynamic, diffraction-limited focus shifting. Here, the mechanical geometry of the membrane is of crucial interest as it must provide sufficient optical performance to allow for diffraction limited focussing and have a high mechanical eigenfrequency to provide dynamic motions. The approach is the analytical consideration of the plate theory and provides the basis for a parameterized finite element model. By means of an finite element analysis (FEA), essential steps for the optimization of the mirror design with respect to a wide range of optical power and a high operating frequency are shown. To verify the results of the FE analysis, the deformed surface is decomposed into Zernike coefficients. An analysis of the point spread function is performed to evaluate the optical performance. For dynamic evaluation a modal and a harmonic vibration analysis are conducted. The opto-mechanical design allows a biconical deformation of the mirror surface, enabling the generation of a diffraction-limited spot diameter in the adjustment range of ±1.2 dpt. The surface shape error in this range is 53 nm. The dynamic analysis shows the first excited eigenfrequency at 21.6 kHz and a diffraction-limited operation frequency at 9.5 kHz. This paper provides an alternative design approach for highly dynamic beam oscillation in the Z direction, forming a complement to highly dynamic X-Y scanning systems.

A method for improving wave suppression ability of acoustic black hole plate in low-frequency range

The acoustic black holes (ABH) with the power-law profile are applied in many fields, such as vibration control, energy collection, etc. It is widely known that the ABH only works above the cut-on frequency. However, few studies improve the vibration suppression performance of acoustic black hole structures below the cut-on frequency. This paper proposes shunt damping to improve the wave suppression ability of an ABH plate in the low-frequency range. The ABH plate with shunt damping obeys the Kirchhoff–Love plate theory. Based on the Hamiltonian principle, the modified Fourier series is selected as the shape function, and the natural frequency of the ABH plate is calculated by the energy method. Compared with the finite element method results, the correctness of this method is verified. Further, comparing the vibration characteristics of the ABH plate with those of the uniform thickness plate, it can be obtained that the ABH plate has excellent vibration damping performance in high frequency but a poor effect in low frequency. Therefore, a shunt damping with blocking circuits is pasted on one side of the central area of the ABH and successfully suppresses four resonate formants in the low-frequency band. Finally, the high-frequency vibration characteristics of the ABH plate with shunt damping are improved by increasing the thickness of the ordinary damping layer. This paper proposes a shunt damping ABH plate composite structure with excellent vibration suppression performance in both the high-frequency and low-frequency range, providing a new idea for the application of two-dimensional ABH plate structures in vibration control.

Physical Insights on Current Dynamics of RESURF DeMOS Designed for High-Frequency CMOS Level Shifter Application

This work investigates isothermal high-current dynamics of Drain-extended MOS (DeMOS) devices optimized for high-frequency switching applications. Gate charge optimized reduced-surface-field (RESURF) DeNMOS structures using surface-implant (P-Top) and split-gate (SG_NonSTI) have been compared with conventional DeNMOS (C_DeNMOS) to investigate the dynamics of parasitic BJT trigger and subsequent space charge modulation (SCM) under high current conditions. Comparative AC analysis at a different gate and drain bias shows quasi-saturation peaks responsible for space charge modulation under high current conditions in DeMOS devices. The transient analysis investigates the isothermal unclamped inductive switching (UIS) and reverse recovery behavior. The parasitic gate capacitances Cgg and Cgd are reduced in both P-Top and SG_NonSTI. With the lowest turn-off delay under very high current conditions in UIS simulations, SG_NonSTI shows the best switching reliability, while P-Top shows the best reverse recovery and transient switching delay performance. In addition, we have shown the application of proposed DeNMOS devices in designing a high-frequency CMOS level shifter circuit. Compared to C_DeNMOS, the highest operating frequency has increased for P-Top and SG_NonSTI DeNMOS structures by 40% and 35%, respectively.

Thermal property evaluation of a 2.5D integration method with device level microchannel direct cooling for a high-power GaN HEMT device

Gallium nitride high electron mobility transistor (GaN HEMT) devices have become critical components in the manufacturing of high-performance radio frequency (RF) or power electronic modules due to their superior characteristics, such as high electron saturation speeds and high power densities. However, the high heat characteristics of GaN HEMTs make device level cooling a critical problem to solve since performance degradation or even failure may occur under high temperatures. In this paper, we proposed a 2.5D integration method with device-level microchannel direct cooling for a high-power GaN HEMT device. To demonstrate this technological concept, a multigate GaN HEMT device featuring a gate length/width/source drain spacing of 0.5 μm/300 μm/6 μm that underwent in-house backside thinning and metallization was used as the test vehicle. A high-resistivity silicon (HR Si) interposer embedded with four-layer microchannels was designed, having widths/pitches of 30 μm/30 μm at the top microchannel. The high-power GaN HEMT device was soldered on a Si interposer embedded with open microchannels for heat dissipation. A pair of GSG Pad chips was soldered simultaneously to display the capacity for the heterogeneous integration of other chip types. Thermal property evaluation was conducted with experiments and simulations. The test results showed that the maximum surface temperature of the GaN HEMT device decreased to 93.8 °C when it experienced a heat dissipation density of 32 kW/cm2 in the gate finger area and an average heat dissipation density of 5 kW/cm2 was found in the active area with the DI water coolant at a flow rate of 3 mL/min. To our knowledge, among recently reported works, this finding was the best cooling capacity of heterogeneously integrated microchannels for GaN HEMT devices. In addition, this technology was scalable regarding the numbers of gate fingers or GaN HEMT devices.

Ultra-thin Fe–Si alloy sheet with excellent high frequency magnetic properties fabricated by partial decarburization combined with multi-stage cold rolling

Transformers with high operating frequencies are highly advantageous owing to their compact sizes. To improve their performance, we successfully fabricated ultra-thin Fe–Si alloy sheets using a novel partial decarburization and multistage cold rolling method. The sheets comprised a high volume fraction of uniform grains under 50 μm with 〈001〉 // rolling direction (RD) texture (78%) and displayed excellent magnetic properties at 20 kHz. Importantly, it was verified that core loss could be controlled by the growth of 〈001〉 // RD grains, and grain size was affected by the sheet thickness and annealing time. The 〈001〉 // RD grains were well developed for sheet thicknesses of 0.05mm–0.07 mm; however, under 0.05 mm, Goss grain growth was hindered by the thickness of the thin sheet. Our specimen achieved a core loss (P0.5/20,000) improvement of about 20% (4.54 W/kg) and one of the highest magnetic flux densities (1.80T) compared with commercial Fe-Si alloy sheets.

Theoretical modelling and experimental investigation on a frequency up-converted nonlinear piezoelectric energy harvester

Ambient vibration energy harvesting has attracted the great attention of numerous researchers to replace the battery power supply strategy of electronic devices. However, the high natural frequency and narrow broadband operation are still significant shortcomings of the conventional vibration energy harvesters to be widely deployed. This paper presents a novel piezoelectric energy harvester (PEH) based on the traditional impact frequency up-converted PEH to achieve lower and broader operating frequency. Nonlinear magnetic force is adopted to regulate the working frequency of PEH. Distributed-parameter modelling and magnetic force simplified modelling are applied in analyzing the piecewise linear dynamic characteristics of the low-frequency driving beam, and the piezoelectric effect is employed for calculating the output voltage of the high-frequency generating beams. Theoretical results comparison between the traditional impact PEH and the proposed novel PEH shows that the introduced nonlinear magnetic force offers a lower initial frequency and broader operating bandwidth. The comparison experimental study achieves a close match to the theoretical results. Under excitation conditions of 3 m/s 2 excitation acceleration, 3 mm impact distance, and 19 mm magnet distance, the initial frequency decreases by about 9.5 Hz, and the operating bandwidth increases from 9 Hz to 16.5 Hz. The maximum power output value of the proposed PEH is 0.491 mW. The novel proposed PEH in this paper provides promising guidance and understanding for energy harvesting in low and broadband environmental vibration. • A novel frequency up-converted nonlinear piezoelectric energy harvester (PEH) is proposed for lower and wider bandwidth energy harvesting. • Developed the theoretical model and analyzed the performance of the device based on averaging method. • The comparison experimental results achieve a close match to the theoretical research that the novel PEH has lower and wider operating frequency than the conventional impact PEH.

A Highly Efficient Si-/SiC-Based Hybrid Active NPC Converter With a Novel Modulation Scheme

With the increasing demand for high-performance power electronic systems, the semiconductor device utilization has gained significant importance. This article proposes the Si/SiC devices based active neutral-point-clamped converter comprising SiC-based H-bridge structure. A novel pulsewidth modulation (PWM) scheme is also proposed that results in an effective utilization of the switching devices. In the proposed converter, the Si devices are soft-switched for all power-factor loading conditions. Therefore, high efficiency can be obtained even at high switching frequency operation with wide range of power factor values. Further, the conduction losses of the SiC <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> s are minimized by strategically selecting the switching states in such a way that the SiC <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> s conduct in parallel conduction paths during the null state operation. This leads to further enhanced efficiency. This article presents the detailed operating principle of the proposed topology operated with the presented PWM scheme. Moreover, a device loss analysis is presented to evaluate the conduction and switching losses of the proposed topology. The presented experimental results validate the performance parameters of the proposed topology with the proposed PWM scheme. Finally, the proposed PWM scheme is compared with the existing PWM schemes using efficiency values of the proposed and some of the prominent existing converter configurations.

Microstructure evolution and soft magnetic property optimization of core-shell FeSiBCCr@SiO2&ZrO2 amorphous magnetic powder cores

In this study, core-shell structured FeSiBCCr@SiO2&ZrO2 amorphous magnetic powder cores (AMPCs) were successfully prepared by the sol-gel method using tetraethyl orthosilicate (TEOS) and zirconium oxychloride hydrate (ZrOCl2·8H2O) as raw materials. The growth mechanism and potential chemical reactions of the SiO2&ZrO2 mixed insulation layer were analyzed by XRD, XPS and SEM‒EDS. In addition, the effect of the insulation layer content on the soft magnetic properties of FeSiBCCr@SiO2&ZrO2 AMPCs was systematically investigated. The SiO2&ZrO2 insulation layer can significantly increase the resistivity, effectively improve the DC bias performance and reduce the core loss of AMPCs. S2* (1.2 mL TEOS and 1.4 g ZrOCl2·8H2O) had a minimum core loss of 2290 mW/cm3 at high frequency (50 mT, 1 MHz). It had a high effective permeability of 48.2 and a superior direct current (DC) bias performance of 77.9% at 8 kA/m. This study provides a valid method to practically produce SMPCs with high resistivity, low core loss at high frequency and excellent DC bias performance through a novel insulation coating process.

Compact tunable filtering balun with stable stopband using varactor‐loaded coupled‐line‐loaded hairpin ring resonator

A tunable filtering balun with compact size and stable stopband is proposed in this article. First, the coupled-line-loaded hairpin ring resonator (C-HRR) is introduced. Then by loading two varactors at the two null-voltage points of the C-HRR, the varactor-loaded C-HRR is designed. The odd-mode resonant frequency fo can be tuned independently without influencing the even-mode resonant frequency fe. Besides, the out-of-phase current distribution of the varactor-loaded C-HRR at fo is noticed. Finally, to validate the features of the varactor-loaded C-HRR, a tunable filtering balun is designed and fabricated. Measured results show that the filtering balun can realize a frequency tuning range from 1.9 to 2.4 GHz. In the tuning process, the amplitude and phase imbalances are less than 0.5 dB and 4° at each tuning state. The lowest spurious resulting from fe is stable and always larger than 2.33fo. The circuit size of the filtering balun is only 0.24λgh × 0.055λgh, where λgh is the guide wavelength at the highest operational frequency.

Efficient and High-Purity Sound Frequency Conversion with a Passive Linear Metasurface.

Despite the significance for wave physics and potential applications, high-efficiency frequency conversion of low-frequency waves cannot be achieved with conventional nonlinearity-based mechanisms with poor mode purity, conversion efficiency, and real-time reconfigurability of the generated harmonic waves in both optics and acoustics. Rotational Doppler effect provides an intuitive paradigm to shifting the frequency in a linear system which, however, needs a spiral-phase change upon the wave propagation. Here a rotating passive linear vortex metasurface is numerically and experimentally presented with close-to-unity mode purity (>93%) and high conversion efficiency (>65%) in audible sound frequency as low as 3000Hz. The topological charge of the transmitted sound is almost immune from the rotational speed and transmissivity, demonstrating the mechanical robustness and stability in adjusting the high-performance frequency conversion in situ. These features enable the researchers to cascade multiple vortex metasurfaces to further enlarge and diversify the extent of sound frequency conversion, which are experimentally verified. This strategy takes a step further toward the freewheeling sound manipulation at acoustic frequency domain, and may have far-researching impacts in various acoustic communications, signal processing, and contactless detection.

Timing, approach, and treatment strategies for infected pancreatic necrosis: a narrative review

Timing, approach, and treatment strategies for infected pancreatic necrosis: a narrative review

(Invited) Development of 3-inch AlN Single Crystal Substrates

Aluminum nitride (AlN) holds great promise as a substrate for electronic devices such as high-power switches, high power density, high frequency and high operating temperature devices for RF. This promise is largely due to its superior properties, for instance its ultra-wide bandgap (UWBG) of 6.2 eV, high thermal conductivity (> 290 W/m*K), high melting point (> 2800°C), relatively good chemical resistance, similarity of its lattice structure and parameters to that of Gallium nitride (GaN), high hardness value of about 12 GPa (at 1 N using Vickers indenter), etc. Presently AlN substrates are successfully used for fabrication of ultraviolet (UV) light emitting diodes (LEDs) operating at wavelengths shorter than 280 nm, i.e., in the UVC region of the spectrum. The AlN-based UVC LEDs are employed in water disinfection, surface cleaning, air purification, and environmental sensing. Several factors including substrate availability, size, production capacity, quality, and cost influence the commercialization of the aluminum nitride both as an UWBG and as an opto-electronic substrate. In this work we present the present and future outlook for the AlN substrates made using Physical Vapor Transport (PVT) growth technique.The PVT crystal growth method of aluminum nitride is carried out in a Tungsten crucible that accommodate the AlN source material as well as the (0001) oriented AlN seed. The thermal gradient is provided by an rf-heating plus appropriate shielding and insulation. In this setup, the sublimed source material is transported to the Al-polar face of the seed where it incorporates into a single crystal. The AlN crystals are then oriented, sliced, and polished. The resulting 2-inch substrates are tested to meet certain specification needed for further epitaxial growth and LED processing. The two-inch AlN wafer specification as well as number of physical properties and purity were previously reported [1].In addition to the 2-inch AlN crystal growth there is an ongoing effort to increase the substrate diameter. Large-diameter (e.g. 100 mm) AlN substrates are a practical requirement benefiting high power electronic devices. Again, PVT growth method is used to expand the crystal size and diameter. However, several challenges have yet to be resolved en route to 100 mm diameter crystals. These challenges are associated with increased thermally induced stress, the need for better control of the axial/radial thermal gradients, vendor ability to provide materials, maintaining crystal quality during expansion, etc.Our PVT growth technique demonstrates high crystal growth yield which allows to contain relatively low production cost. Furthermore, we have established a high-capacity process capable to produce many thousands of 2-inch AlN substrates per year. Our current crystal growth process also demonstrated greater than 3-inch diameter single-crystal AlN substrates; properties of such wafers will be reported. Robert T Bondokov et al 2021 ECS Trans. 104 37

Investigating Gate Interface Traps in β-Ga2O3 Field Effect Transistors (MOSFETs) By Using the Transfer Length Method (TLM) and UV Exposure

Beta-gallium oxide (β-Ga2O3) is a promising ultra-wide bandgap semiconductor for high power electronic applications due to its high theoretical critical field of 8 MV/cm, and Baliga figure of merit (BFOM) of ~3300, 3 – 10 times larger than current state-of-the-art wide bandgap semiconductors. β-Ga2O3 field-effect transistors (FETs) have been explored for both high power and radio frequency (RF) operation, but with relatively high parasitic resistances. A method is developed to determine the contact, series, and channel resistances in depletion mode β-Ga2O3 MOSFETs. The Al2O3-β-Ga2O3 interface is primarily important in the performance of β-Ga2O3 FETs due to charge trapping. Measurements will be performed with UV and visible light radiation to study the role of trap states on the FET resistances and device performance.Here, we report on using a modified transfer length method (TLM) to determine the contact, series, and channel resistances from planar, depletion-mode β-Ga2O3 FETs. The results are compared with respect to conventional TLM structures fabricated on the same wafer. The β-Ga2O3 FETs and TLM structures are fabricated on a (010) semi-insulating β-Ga2O3 substrate. The channel layer is a 50 nm Si-doped epi-layer with a target concentration of 2.4 x 1018 cm-3. A Ti/Al/Ni/Au metal stack is deposited and annealed to form Ohmic contacts. The gate dielectric is composed of atomic layer deposition-grown aluminum oxide (Al2O3, 20 nm). The structures have a constant gate length, LG, of 1.94 μm, while the total source-drain spacing, LSD, varies as 3μm, 8 μm, and 13 μm. Transfer characteristics were measured at room temperature and low drain-source voltage, VDS, of 0.01 V. The threshold voltage, VTH, was determined to be » -4V for all MOSFET devices. Measurements were performed in the dark or under UV (265 nm, 2.8 W/cm2) exposure.Conventional TLM structures were measured in the dark and with UV exposure, and a 40% decrease in the sheet resistance was observed when exposed to UV. We attribute this change to an increase in the carrier concentration from photo-generated electrons due to trap states within the β-Ga2O3. We also performed I-V measurements of the FETs in the dark and observed hysteresis behavior with respect to gate-source voltage, VGS, which we attribute to trapped charge at the Al2O3-β-Ga2O3 interface. Using the TLM method, we developed a methodology to extract the β-Ga2O3 MOSFET channel sheet resistances within the gated (Rsh,G) and ungated (Rsh) regions as a function of VGS. We observe a significant decrease in Rsh,G from 288 ± 14 kΩ sq-1 to 7.6 ± 0.38 kΩ sq-1 as VGS varies from -3 V to 3 V. The sheet resistance in the ungated regions, Rsh, shows a negligible change from 28 ± 1.4 kΩ sq-1 above a VGS of -1.8 V, comparable to that of the conventional TLM structures, but begins to increase with more negative VGS, reaching 90 ± 4.5 kΩ sq-1 at a VGS of -3 V. The VGS dependence of Rsh is due to complicated current flow mechanisms when the depletion region is large, which is not considered in this model. We will extend the study by performing I-V measurements with UV and visible light radiation to observe any effect of traps at the Al2O3-β-Ga2O3 interface has on Rsh and Rsh,G.