MHz Frequency Range Research Articles

Adjustable low‐profile compact AIS antenna with reduced ground‐size sensitivity

AbstractThis letter presents a novel reconfigurable low‐profile Automatic Identification System antenna that exhibits insensitivity to ground size. The antenna's physical dimensions measure 340 mm × 230 mm × 83 mm. Typically, smaller antennas require larger ground planes. However, changes in ground size cause the resonant frequency of the small antenna to shift, thereby limiting its working environment. Consequently, the antenna cannot function in systems with varying ground areas. To address this issue, a reconfigurable Inverted‐F antenna loaded with shorted parasitic elements is proposed. By switching the shorted state of a parasitic element, the antenna can operate within the required frequency band for different ground sizes. Simulated results demonstrate that the antenna can cover the 161–163 MHz frequency range when the ground size ranges from 250 × 250 to 450 × 450 mm2 with a shorted parasitic element. When the parasitic unit is not shorted, the antenna can cover the same frequency range when the ground size ranges from 450 × 450 mm2 to infinity. The proposed antenna achieves the characteristic of being insensitive to ground‐size changes in two states, and is widely applicable to devices with different ground sizes (such as ships and airplanes, etc.), reducing the cost of the system.

Dielectric properties of tobacco and tomato plant leaves over a broad frequency range

Complex permittivity of tomato and tobacco leaves have been measured over the 20 Hz − 2 MHz frequency range using a precision LCR-Meter, and over frequency range from 500 MHz to 15 GHz using a Vector Network Analyzer. Complex permittivity of leaves is found to increase as the moisture content in the leaves increases, at a fixed frequency. At lower frequencies, the dielectric constant ε’ of leaves decreases with increase in frequency up to 2 MHz. At 2 MHz, the complex permittivity ε* = ε′ – jε″ for Tobacco leaves varies from 3855 – j 2863 to 6.12 – j 0.29 with decrease in moisture content, whereas for Tomato leaves ε* varies from 5900 – j 3116 to 3.06 – j 0.29 with decrease in moisture contents in the leaves. Over the microwave frequency range, the dielectric constant and dielectric loss of low moist leaves decreases with increase in frequency. For the leaves having higher moisture content, the dielectric loss decreases rapidly with increase in frequency from 500 MHz to about 5 GHz, after which it starts to increase with increase in the frequency, approaching a relaxation peak. At 14 GHz, the complex permittivity ε* for Tobacco leaves varies from 26.86 – j 26.45 to 2.31 – j 0.034 with decrease in moisture content, whereas for Tomato leaves ε* varies from 23.37 – j 17.50 to 1.67 – j 0.004 with decrease in moisture contents in the leaves. A good agreement is observed between measured values of complex permittivity, with the values calculated using Debye-Cole dual-dispersion dielectric model. Brewster’s angle corresponding to vertical polarization in emissivity calculation is found to increase with increase in moisture content in the leaves.

Bubbles as high-frequency rheometers for soft matter characterization

Precise knowledge of bubble dynamics in tissue is essential for optimizing both ultrasound imaging and ultrasound therapy. Great efforts have therefore been made, over the past decade, to model the behavior of (micro)bubbles in viscoelastic materials. This has led to a series of models based on modified Rayleigh–Plesset equations. Last to date, we propose a novel generalized model build on finite strain theory and relaxation functions. At this stage however, the bottle neck remains our limited knowledge of tissue viscoelasticity at high strain rates, which is a necessary input to any theoretical model. Indeed, traditional rheometers cannot reach frequencies above 1kHz, which is 3 orders of magnitude below the desired MHz frequencies. We will show how ultrasound-driven bubbles can be used as microscale rheometers. More specifically, we use the volumetric oscillations of (monodisperse) phospholipid-coated microbubbles embedded in hydrogels to measure the storage and loss moduli in the MHz frequency range. In addition, we can bridge the gap between kHz and MHz using the surface modes of cylindrical microbubbles trapped in micropits. These oscillations can be both modelled and simulated, and provide access to the effective surface tension and viscosity in the range of 50 to 500 kHz.

Blind-label acoustic subwavelength imaging

There is a long-existing tradeoff between the imaging resolution and the penetration depth in acoustic imaging caused by the diffraction limit. Most of the existing subwavelength imaging approaches that address this trade-off require exogenous “labels,” such as metamaterials or contrast agents, to be deposited close to the objects. Those labels need to either remain static or be tracked precisely during imaging, therefore, are extremely restrictive in practical applications. This talk will present our recent work on a “blind label” approach for acoustic subwavelength imaging. The “blind labels” are randomly distributed acoustic scatterers with deep-subwavelength sizes whose exact locations and trajectories are unknown. A hardware/software co-design framework is developed that is composed of two parts: 1) spatial mixing: a physical process that converts the originally evanescent components in the scattered waves from the object to propagating components that can reach the far-field detector; 2) computational image reconstruction. Our experiments both in air at KHz frequency range and in water at MHz frequency range achieved multi-fold resolution enhancement. The proposed “blind-label” approach relaxes the restrictions of depositing controlled labels close to the object, therefore significantly improving the practicality of acoustic subwavelength imaging in acoustic sensing, imaging, and communication applications.

Experimental demonstration of weak-light inter-spacecraft clock jitter readout for TianQin.

The space-based gravitational wave detection mission, TianQin, requires high-level synchronization between independent clocks of all spacecrafts to extract the gravitational wave signals. It is necessary to measure the inter-spacecraft relative clock jitter based on laser phase-sideband clock transfer. The main challenge is the tracking and locking of clock sideband beatnote signals with low signal-to-noise ratio and frequency variation. In this paper, a systematic scheme of inter-spacecraft clock jitter readout is reported. The requirement of the clock transfer link for TianQin based on the time-delay interferometry algorithm is derived. A bi-directional laser interferometer system with a transmission optical power below 1 nW and a time delay of ∼50 µs is built up to demonstrate the weak-light clock transfer. In this scheme, frequency modulation is performed on the laser to simulate the inter-spacecraft Doppler frequency shift and its variation. Based on electrical and optical clock transfer comparison experiments, it is demonstrated that the GHz frequency synthesizer is the main noise source below the 50 mHz frequency range. The residual clock jitter noise introduced by the optical transfer link is below 40 fs/Hz1/2 above the 6 mHz frequency range, and the fractional frequency instability is less than 6.7 × 10-17 at 1000 s, which meets the requirement of the TianQin mission. Ultimately, The carrier phase measurement accuracy reaches 1 × 10-4 cycles/Hz1/2 above 6 mHz after differential clock noise correction using measured clock jitter.

Vibrational study and effect of copper substitution on the electrical properties of the (C2H5NH3)2CdCl4 hybrid compound

In this paper, elaborated samples (C2H5NH3)2CdCl4 and (C2H5NH3)2Cd0.5Cu0.5Cl4 have been studied by X-ray powder diffraction patterns, Raman and impedance spectroscopy. X-ray diffraction indicates that these compounds crystallize at room temperature in the orthorhombic system. The values of lattice parameters and volume were determined. Raman spectroscopy (RS) analysis was used to identify the different modes of vibration between atoms. This technique confirms the presence of the organic and inorganic chain of the hybrid compounds. The morphological analysis was carried out, and the size of the grain was ascertained using the Image J application. The electrical measurements were performed in the 5 Hz – 10 MHz frequency range and 0–6 V bias voltage interval. The capacitance behavior as a function of frequency is explained by the interface states effect. It is noted that the capacitance increases with the introduction of copper in (C2H5NH3)2CdCl4 hybrid compound. The C–V curves show three regions of electronic charge distribution: (a) inversion, (b) depletion and (c) accumulation. The frequency dependence of the conductivity is interpreted in term of Jonscher law. The increase of the conductivity is attributed to the incorporation of copper in (C2H5NH3)2CdCl4 compound.

Assessment of the electromagnetic field exposure due to wireless communication technologies in two university campuses of medellin, Colombia

Exposure to radiofrequency electromagnetic fields (RF-EMFs) is considered an area of significant importance in the medical and scientific community. However, the availability of exposure data for indoor and outdoor locations in universities is limited and currently inconsiderate in Latin America. The aim of this work was to evaluate the electric field levels due to mobile telecommunication technologies and Wi-Fi to which students and faculty staff from two campuses of a higher education institution are exposed. Using a portable spectrum analyzer, we carried out 516 short-term measurements in the 800–3000 MHz frequency range at both indoor and outdoor locations. These locations were chosen to cover all areas of the assessed buildings. The electric field differences between floors and buildings are discussed. Finally, we compared the electric field levels with exposure limits. The highest electric field level measured was 13.97 V/m at the 850 MHz band. However, the average electric field values were below 2 V/m. The greatest contribution to the total electric field was due to sources using the 850 MHz and 1900 MHz bands (98%), while the contribution of the Wi-Fi network was low (1.0%). The results show that all the electric field levels measured were lower than the ICNIRP reference levels for radio-frequency exposure.

Physics Based Temperature Dependent EIS Simulation on 18650 NMC/Graphite Cell

Electrochemical Impedance Spectroscopy (EIS) is a non-destructive method that provides crucial insights regarding the battery processes. EIS is mainly done by applying a small amplitude AC with a 10 mHz to 1 MHz frequency range. One can determine the electrolyte's ohmic resistance, the Solid Electrolyte Interface (SEI) capacitance, electron transfer rate and the diffusion mechanisms at separate frequency regions from each other.One disadvantage of EIS is the ambiguity of the analyses of the data. The equivalent circuit models used are not unique, and the correspondence between the various elements in the equivalent circuits to electrochemical phenomena are suspect. A new approach on EIS analysis is sought after in order to improve the interpretation. For example, distribution of relaxation times (DRT) was proposed by Zhang et al. in 2015 .Using physics-based models in order to model EIS has been published by Murbach and Schwartz in 2018. In their work, they created a physics-based simulation which uses a pseudo two-dimensional battery model. Their main aim was to present a new approach to EIS data analysis by using a physics-based model rather than equivalent circuit models. They created a data set with 38.800 separate spectra and match the experimental data by using least squares matching approach with the previously computed data. Though this work improved the understanding, multiple calculated data sets matched the experiments with similar errors.Ultimately, in order to achieve an EIS analysis method that is directly related to the fundamental parameters regarding the electrochemistry, degeneracies have to be removed via temperature dependence and the non-linearities as extra dependent variables. This way, the ambiguities and the suspicious parameter assigning can be fixed.We will be reporting on T-dependent linear and nonlinear simulations on 18650 NMC/Graphite battery. All the simulations were done on Python by using a physics-based model PyBaMM (Sulzer, Valentin, et al. "Python battery mathematical modelling (PyBaMM)." Journal of Open Research Software 9.1 (2021).). Impedance data was obtained via simulating voltage as a function of current within 100 µHz to 10 kHz frequency range. Temperature range was set to -25°C to 65°C with 10°C increments. The linear and non-linear impedance is analyzed as a function of temperature. Our results will be compared with experimental temperature dependent linear/nonlinear spectra in order to obtain proper fundamental parameters

Design of a multi‐function global navigation satellite system and 5G cellular antenna structure for automotive applications using characteristic mode analysis

AbstractThis paper illustrates a single antenna structure that simultaneously satisfies the antenna requirement for 5G cellular and global navigation satellite systems (GNSS). The antenna has a linearly polarised omnidirectional radiation for the newly defined 5G sub‐6 GHz cellular bands in the 617–5000 MHz frequency range. In contrast, a right‐hand circular polarisation (RHCP) with a hemispherical radiation pattern at the GNSS L1 has a frequency range of 1559–1606 MHz. This multi‐function antenna would provide a simplified product design and better space utilisation, particularly suitable for flat antenna modules and automotive. The primary concept involves employing a planar inverted F antenna structure to generate radiation modes for cellular bands and incorporate U‐slot on the top plate to generate the GNSS radiation modes. The design methodology utilises the characteristic mode analysis tool to tune the desired radiation characteristic mode at the intended frequency range for each function. The antenna was fabricated, and the performance was evaluated on a 1‐m ground plane. The GNSS RHCP gain measures 5 dBc at boresight, with an axial ratio below 2 dB across the L1 bands, while the cellular gain maintains an excellent return loss and omnidirectional radiation pattern performance across the cellular bands.

Crystal Structure, Magnetic, and Dielectric Properties of (x)CoFe2O4–(1−x)Ba0.8Sr0.2TiO3 Multiferroics

The composites (x)CoFe2O4–(1−x)Ba0.8Sr0.2TiO3 are prepared by solid‐state reaction method using microwave double‐step sintering. Ba0.8Sr0.2TiO3 crystallizes to tetragonal crystal symmetry with P4mm space group and CoFe2O4 crystallizes to cubic crystal symmetry with space group. Electron microscopy techniques are used to understand the microstructure, elemental composition, and morphology of the composites. The dielectric properties are measured in the 1 Hz–1 MHz frequency range and 40–400 °C temperature range. Composite with x = 0.1 (ε′ ≈ 170, tan δ = 0.08 at 1 kHz) and 0.2 (ε′ ≈ 390, tan δ = 0.07 at 1 kHz) has better dielectric properties than the parent Ba0.8Sr0.2TiO3 ferroelectric (ε′ ≈ 125, tan δ = 0.16 at 1 kHz) and CoFe2O4 ferrimagnetic phases (ε′ ≈ 375, tan δ = 0.72 at 1 kHz), respectively. Composite with 10% cobalt ferrite has the highest saturation polarization (2.1 μC cm−2), the highest remanent polarization (0.9 μC cm−2), and coercive field (23.9 kV cm−1) compared to ferroelectric phase followed by x = 0.2 composite (PS = 1.6 μC cm−2, Pr = 0.8 μC cm−2, and EC = 19.2 kV cm−1). Composite with x = 0.2 shows the highest magnetic coercive field of 1.96 kOe. Hence, this article advocates that 20% ferrite in the composites is the optimized composition for multiferroic applications. The present study will help to explore piezoelectric, magnetostrictive, and magnetoelectric properties of (x)CoFe2O4–(1−x)Ba0.8Sr0.2TiO3 for the technological application.

The structure perfection studies of LiCaAlF6 crystals by laser acoustics technique

The acoustic properties of LiCaAlF6 crystals and the annealing procedure impact on them were studied. The velocities of longitudinal and shear ultrasonic waves along the direction of the optical c-axis of the crystals were measured by laser acoustics, and the mechanical constants were determined: modules of elasticity, all-round compression, shear, and Poisson's ratio. It has been established that the attenuation coefficient of ultrasonic waves in the 1-15 MHz frequency range can serve as a characteristic of the optical perfection of the crystals. The effect of ultrasonic annealing of LiCaAlF6 crystal samples under prolonged exposure by pulsed ultrasound was discovered.

An eclipsing 47 min double white dwarf binary at 400 pc

ABSTRACT We present the discovery of the eclipsing double white dwarf (WD) binary WDJ 022558.21−692025.38 that has an orbital period of 47.19 min. Following identification with the Transiting Exoplanet Survey Satellite, we obtained time series ground based spectroscopy and high-speed multiband ULTRACAM photometry which indicate a primary DA WD of mass $0.40\pm 0.04\, \text{M}_\odot$ and a $0.28\pm 0.02\, \text{M}_\odot$ mass secondary WD, which is likely of type DA as well. The system becomes the third-closest eclipsing double WD binary discovered with a distance of approximately 400 pc and will be a detectable source for upcoming gravitational wave detectors in the mHz frequency range. Its orbital decay will be measurable photometrically within 10 yr to a precision of better than 1 per cent. The fate of the binary is to merge in approximately 41 Myr, likely forming a single, more massive WD.

Measurements of DC SQUID Damping Effects on Superconducting Resonant Circuits

We present experimental measurements of SQUID-induced damping effects on strongly coupled, lumped-element resonators in the 500kHz-1 MHz frequency range. While dc SQUIDs are commonly used for sensitive readout of electromagnetic signals such as in lumped-element axion dark matter searches, coupling a dc SQUID to a resonant circuit modifies the circuit's resonance frequency, quality factor, noise, and impedance. These parameters have a direct impact on the science reach of axion dark matter detectors, making it important to understand SQUID damping contributions. We describe a helium dip probe and two-stage SQUID readout scheme used to probe SQUID damping effects. Measurements from this setup inform the design and operation of both future test platforms as well as next-generation dark-matter experiments.

Sound speed and attenuation of human pancreas and pancreatic tumors and their influence on focused ultrasound thermal and mechanical therapies.

There is increasing interest in using ultrasound for thermal ablation, histotripsy, and thermal or cavitational enhancement of drug delivery for the treatment of pancreatic cancer. Ultrasonic and thermal modelling conducted as part of the treatment planning process requires acoustic property values for all constituent tissues, but the literature contains no data for the human pancreas. This study presents the first acoustic property measurements of human pancreatic samples and provides examples of how these properties impact a broad range of ultrasound therapies. Data were collected on human pancreatic tissue samples at physiological temperature from 23 consented patients in cooperation with a hospital pathology laboratory. Propagation of ultrasound over the 2.1-4.5MHz frequency range through samples of various thicknesses and pathologies was measured using a set of custom-built ultrasonic calipers, with the data processed to estimate sound speed and attenuation. The results were used in acoustic and thermal simulations to illustrate the impacts on extracorporeal ultrasound therapies for mild hyperthermia, thermal ablation, and histotripsy implemented with a CE-marked clinical system operating at 0.96MHz. The mean sound speed and attenuation coefficient values for human samples were well below the range of values in the literature for non-human pancreata, while the human attenuation power law exponents were substantially higher. The simulated impacts on ultrasound mediated therapies for the pancreas indicated that when using the human data instead of the literature average, there was a 30% reduction in median temperature elevation in the treatment volume for mild hyperthermia and 43% smaller volume within a 60°C contour for thermal ablation, all driven by attenuation. By comparison, impacts on boiling and intrinsic threshold histotripsy were minor, with peak pressures changing by less than 15% (positive) and 1% (negative) as a consequence of the counteracting effects of attenuation and sound speed. This study provides the most complete set of speed of sound and attenuation data available for the human pancreas, and it reiterates the importance of acoustic material properties in the planning and conduct of ultrasound-mediated procedures, particularly thermal therapies.

Shear and longitudinal attenuations and quality factors of poly(methyl metacrylate) (PMMA) from 20 kHz to 12 MHz investigation with ultrasonic spectroscopy

PMMA is often considered as a calibration material for experimental benches dedicated to viscoelasticity investigation. Nevertheless, regarding literature, data concerning attenuation coefficients and quality factors are essentially available in the MHz frequency range and results in the low-frequency range are scarce and scattered. In this communication, thanks to the use of high-frequency ultrasonic spectroscopy between 2 and 8 MHz in the range 6 °C − 45 °C, Time-Temperature Superposition principle and Resonant Ultrasonic Spectroscopy (RUS), we show that both longitudinal and shear quality factors of PMMA decrease considerably for low frequencies (<MHz), and that the classically accepted linear laws describing attenuation as a function of frequency are valid only beyond several MHz. This variation is attributed to secondary relaxation processes such as γ relaxation considering the activation energy deduced from experimental data. Power laws are proposed to describe the evolution of quality factors and attenuation coefficients versus frequency in the 20 kHz − 12 MHz range.

MI-Sensor Element Features and Estimation of Penetration Depth and Magnetic Permeability by Magnetoresistance and Magnetoreactance of CoFeSiB Amorphous Wires

The magnetoimpedance (MI) of amorphous soft magnetic Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">68.15</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4.35</sub> Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12.5</sub> B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">15</sub> wires produced by the in-rotating water quenching technique was systematically studied. The behavior of the MI-element designed for magnetic sensors was examined in an external longitudinal dc magnetic field in the low-frequency range (f ≤ 1 MHz) and at the beginning of the intermediate frequency range (2 MHz ≤ f ≤ 5 MHz). A critical frequency of about 5 kHz - 7 kHz was observed with an initial increase in the MI effect. A maximum MI ratio of 334% was recorded at 0.95 MHz in a magnetically saturated MI-element. The intermediate frequency range is explored using the magnetoresistive - MR and magnetoreactive - MX components of magnetoimpedance Z. The MI anisotropy field profile occurs in the MHz operating frequency range with values increasing up to 25 A/m, exhibiting frequency dependence. The magnetic penetration depth was calculated using experimental magnetoresistance data, and the values obtained were about 3 μm - 4 μm for 5 MHz, showing a saturation trend. The magnetic permeability is analyzed in the framework of the electromagnetic classical high-limit model of a cylinder, which includes penetration depth and magnetoreactance. In our experiments and calculations, the classical high limit is satisfied in the operating frequency range of a few MHz. The magnetic permeability peak value is about 35% lower than the comparable data of amorphous CoFeNiMoSiB glass-coated microwires.

Nanocomposites based on porous silicon and reduced graphene oxide for ionizing radiation sensing

In this study, the field-effect transistor (FET) based on the oxidized porous silicon (PS) – reduced graphene oxide (rGO) sandwich-like composite has been created. The electrical characteristics of the obtained FET were studied in both DC and AC modes. I-V curves and switching characteristics of the PS–rGO-based FET were analyzed. An increase in resistance and a decrease in capacitance of the experimental structures have been found in the 25 Hz − 1 MHz frequency range due to the joint action of α-, β-, and γ-radiation. The parameters of the equivalent circuit model of the PS–rGO-based FET before and after irradiation with 226Ra isotope have been determined using the impedance spectra. The formation of radiation-induced defects and the charge accumulation in the PS layer is considered a possible mechanism of the ionizing radiation influence on the graphene FET conductivity. The FET based on the PS–rGO structures has a high potential for application in ionizing radiation sensors due to the linear dependencies of resistance and capacitance on the irradiation duration.

Utilization of the 915 MHz LoRa Communication Module as a Navigational Tool in Rural Areas

The high interest of mountain climbers in Indonesia also increases the risk of accidents that can occur in climbing. To reduce this risk, we need a tool system that can assist local officers in monitoring the location and condition of climbers. However, due to the many signal limitations and internet connections in mountainous terrain or rural areas, there is a need for other alternative media that can be used to monitor climbers' location and conditions. The LoRa (Long Range) communication module can solve the mountain's limited signal and internet connection. Navigation uses the LoRa SX1276 module based on Radio Frequency (RF) as the transmission medium in the 915 MHz frequency range. The data transmission uses the repeater principle as a bridging medium between devices which can then be displayed via the Android application via Cloud Firestore or Bluetooth media. From the results of the tests that have been carried out, it can be concluded that the system works well in transmitting data via Radio Frequency (RF) with an average RSS reduction of -5.1 dBm every 45 m at a radius of 450 m, Cloud Firestore with an average delay of 0.3855 seconds and Bluetooth with reduced RSSI of -5.5 dBm every 5 m with a maximum radius of 50m.&#x0D; Keyword—Radio Frequency(RF), Wireless, Aplication Android, Cloud Firestore, LoRa.

Toward a Smart Sensing System to Monitor Small Animal's Physical State via Multi-Frequency Resonator Array.

This article presents a highly scalable and rack-mountable wireless sensing system for long-term monitoring (i.e., sense and estimate) of small animal/s' physical state (SAPS), such as changes in location and posture within standard cages. The conventional tracking systems may lack one or more features such as scalability, cost efficiency, rack-mount ability, and light condition insensitivity to work 24/7 on a large scale. The proposed sensing mechanism relies on relative changes of multiple resonance frequencies due to the animal's presence over the sensor unit. The sensor unit can track SAPS changes based on changes in electrical properties in the sensors near fields, appearing in the resonance frequencies, i.e., an Electromagnetic (EM) Signature, within the 200 MHz-300 MHz frequency range. The sensing unit is located underneath a standard mouse cage and consists of thin layers of a reading coil and six resonators tuned at six distinct frequencies. ANSYS HFSS software is used to model and optimize the proposed sensor unit and calculate the Specific Absorption Rate (SAR) obtained under 0.05 W/kg. Multiple prototypes have been implemented to test, validate, and characterize the performance of the design by conducting in vitro and in vivo experiments on Mice. The in-vitro test results have shown a 15 mm spatial resolution in detecting the mouse's location over the sensor array having maximum frequency shifts of 832 kHz and posture detection with under 30° resolution. The in-vivo experiment on mouse displacement resulted in frequency shifts of up to 790 kHz, indicating the SAPS's capability to detect the Mice's physical state.

Modeling and Prediction of Common Mode Electromagnetic Interference in GaN-Based Switching Power Converters

Behavioral models of common mode (CM) electromagnetic interference (EMI) are proposed herein for a GaN high-electron-mobility transistor (HEMT) synchronous buck converter. First, a CM noise model is developed using a linear equivalent circuit that consists of a voltage source, current source, and two noise impedances. The behavioral parameters of the CM model are then extracted by changing the input-side shunt impedances. A GaN HEMT buck converter setup is then built using switching frequencies of 100 kHz, 200 kHz, and 500 kHz to verify the validity of the CM EMI behavioral model. A comparison between the experimental and predicted results indicated that the proposed CM EMI model of GaN-based power converters was able to predict well the CM EMI current in the 150 kHz–30 MHz frequency range.