Full Electromagnetic Simulation Research Articles

MRI retrospective respiratory gating and cardiac sensing by CW Doppler radar: A feasibility study.

This study investigates the feasibility of non-contact retrospective respiratory gating and cardiac sensing using continuous wave Doppler radar deployed in an MRI system. The proposed technique can complement existing sensors which are difficult to apply for certain patient populations. We leverage a software-defined radio for continuous wave radar at 2.4 GHz to detect in-vivo respiratory and cardiac timescrolled signals. In-bore radar signal demodulation is verified with full electromagnetic simulations, and its functionality is validated on a test bench and within the MR bore with four normal subjects. Radar sensing was compared against well-known references: electrocardiography on a test bench, system bellows, and pulsed plethysmography sensors with in the MRI bore. The feasibility of noncontact cardiac rate sensing, dynamic breathing sequence synchronization, and in-bore motion correction for retrospective respiratory gating applications was demonstrated. Optimal radar front-end system arrangement, along with spectral isolation and narrow bandwidth of operation, enable MRI-compatible and interference-free motion sensing. The signal-to-noise-ratio degradation by the radar integration was within 4.5% on phantom images. We confirmed that in-bore retrospective motion correction using CW Doppler radar is feasible without MRI system constraints. Non-contact motion correction sensing in MRI may provide better patient handling and through put by complementing existing system sensors and motion correction algorithms.

Non-contact imaging of terahertz surface currents with aperture-type near-field microscopy

Terahertz (THz) near-field imaging and spectroscopy provide valuable insights into the fundamental physical processes occurring in THz resonators and metasurfaces on the subwavelength scale. However, so far, the mapping of THz surface currents has remained outside the scope of THz near-field techniques. In this study, we demonstrate that aperture-type scanning near-field microscopy enables non-contact imaging of THz surface currents in subwavelength resonators. Through extensive near-field mapping of an asymmetric D-split-ring THz resonator and full electromagnetic simulations of the resonator and the probe, we demonstrate the correlation between the measured near-field images and the THz surface currents. The observed current dynamics in the interval of several picoseconds reveal the interplay between several excited modes, including dark modes, whereas broadband THz near-field spectroscopy analysis enables the characterization of electromagnetic resonances defined by the resonator geometry.

Ultra-Wideband Multi-Octave Planar Interconnect for Multi-Band THz Communications

An ultra-wideband (UWB) interconnect technology using indium phosphide (InP)-based transitions for coupling the output signals from terahertz (THz) photodiodes featuring coplanar waveguide (CPW) outputs to low-loss dielectric rod waveguides (DRWs) is presented. The motivation is to exploit the full bandwidth offered by THz photodiodes without limitations due to standard rectangular waveguide interfaces, e.g., for future high data rate THz communications. Full electromagnetic wave simulations are carried out to optimize the electrical performance of the proposed InP transitions in terms of operational bandwidth and coupling efficiency. The transitions are fabricated on 100-µm-thin InP and integrated with silicon (Si) DRWs. Experimental frequency domain characterizations demonstrate efficient THz signal coupling with a maximum coupling efficiency better than − 2 dB. The measured 3-dB and 6-dB operational bandwidths of 185 GHz and 280 GHz, respectively, prove the multi-octave ultra-wideband features of the developed interconnect technology. The 6-dB operational bandwidth covers all waveguide bands between WR-12 to WR-3, i.e., a frequency range between 60 and 340 GHz. In addition, the multi-octave performances of the fabricated interconnects were successfully exploited in proof-of-concept THz communication experiments. Using intermediate frequency orthogonal frequency division multiplexing (OFDM), THz communications are demonstrated for several frequency bands using the same interconnect. Considering soft-decision forward error correction, error-free transmission with data rates of 24 Gbps at 80 GHz and 8 Gbps at 310 GHz is achieved.

State Residualisation and Kron Reduction for Model Order Reduction of Energy Systems

Greater numbers of power electronics (PEs) converters are being connected to energy systems due to the development of renewable energy sources, high-voltage transmission, and PE-interfaced loads. Given that power electronics-based devices and synchronous machines have very different dynamic behaviours, some modelling approximations, which may commonly be applied to run transient simulations of transmission systems, may not be optimal for future grids. Indeed, the systematic utilisation of the phasor approximation for power lines, implemented in most transient simulation programs, is increasingly not appropriate anymore. In order to avoid the requirement for full electromagnetic transient simulations, which can be resource-demanding and time-consuming, this paper proposes a combination of an event-based state residualisation approximation and the Kron reduction technique. The proposed technique has the advantage of allowing accurate transient simulations based on the optimal reduction of the number of state variables, depending on the observed variables, the considered events, and the tolerated approximation error, along with simplifying power systems equations for accelerated simulations.

Dynamic phasor-based hybrid simulation for multi-inverter grid-connected system

To realize the efficient transient simulation of a grid-connected power generation system based on multiple inverters, this paper proposes a hybrid simulation method integrating the models of electromagnetic transient and dynamic phasors. Based on a demonstration of the concepts and properties of dynamic phasors, the models of single-phase and three-phase inverters described by dynamic phasors are established first. Considering the numerical compatibility problem between dynamic phasors and instantaneous values, an interface scheme between dynamic phasors and instantaneous values is designed, and the efficiency and precision differences of various transformation methods are compared in detail. Finally, by utilizing MATLAB/Simulink, a hybrid simulation platform of a multi-inverter grid-connected system is built, and the efficiency and accuracy of the hybrid simulation are validated via comparison with the full electromagnetic transient simulation.

Efficiency Bound Estimation for a Practical Microwave and mmWave Wireless Power Transfer System Design

In this study, we present an efficient method to find the power transfer efficiency (PTE) bound for practical microwave and mmWave wireless power transfer (MPT) systems composed of transmitter (Tx) and receiver (Rx) array antennas. The PTE bound of the MPT system is obtained by formulating it as a convex optimization problem (CVP) that maximizes the power received at the Rx array under the transmit power constraint. The channel state information (CSI) between each element of the Tx and the Rx is the input parameter of the proposed CVP. The CSI is estimated using the Friis transmission equation and the active element pattern of the array antenna because the Tx and the Rx are assumed to be large arrays. For an MPT system designed at 10 GHz and 24 GHz, the estimated PTE bound is compared to those in previous studies while varying the distance and tilted angle between the Tx and the Rx. The computation times required for the methods are compared. The numerical results show that the proposed method provides a faster and more accurate PTE bound without full electromagnetic simulation of the MPT system consisting of Tx and Rx array antennas. This study's results will serve as guidelines for practical MPT system design in the future.

Resonant electric probe to axionic dark matter

The oscillating light axion field is known as wave dark matter. We propose an LC (inductor-capacitor)-resonance enhanced detection of the narrow band electric signals induced by the axion dark matter using a solenoid magnet facility. We provide full 3D electromagnetic simulation results for the signal electric field. The electric signal is enhanced by the high $Q$-factor of a resonant LC circuit and then amplified and detected by the state-of-the-art cryogenic electrical transport measurement technique. The cryogenic amplifier noise is the dominant noise source in the proposed detection system. We estimate that the detection system can have a promising sensitivity to axion dark matter with mass below ${10}^{\ensuremath{-}6}\text{ }\text{ }\mathrm{eV}$. The projected sensitivities improve with the size of the magnetic field, and the electric signal measurement can be potentially sensitive to the quantum chromodynamics (QCD) axion with ${g}_{a\ensuremath{\gamma}}\ensuremath{\sim}{10}^{\ensuremath{-}16}\text{ }\text{ }{\mathrm{GeV}}^{\ensuremath{-}1}$ around ${m}_{a}\ensuremath{\sim}{10}^{\ensuremath{-}8}\text{ }\text{ }\mathrm{eV}$, with a multimeter scale magnetized region. This limit is around five orders of magnitude below the current constraint from the cosmic rays.

Cervical Tissue Hydration Level Monitoring by a Resonant Microwave Coaxial Probe

Cervical tissue hydration level is one of the most important parameters to monitor in the early diagnosis of preterm birth. Electrical-impedance-spectroscopy-based techniques are often used, but they suffer from limited accuracy. Open microwave coaxial probes have been widely used as a broadband dielectric characterization technique for human tissue samples due to their versatility, but with limited accuracy due to their nonresonant nature. In this work, a resonant microwave open coaxial probe with multiple harmonic resonances is proposed as a sensing platform for tissue-hydration-level monitoring. The mechanical design was analyzed and verified by finite-element full 3D electromagnetic simulation and experiments. Dominant sources of errors and the ways to mitigate them were discussed. In vitro experiments were carried out on human cervix samples to verify the precision and accuracy by comparing the results to a commercial skin-hydration sensor. The proposed sensor shows mean fractional frequency shift of (3.3 ± 0.3) × 10-4 per unit % over the entire data. This translates into an absolute frequency shift (ΔfN) of 252 ± 23 kHz/%, 455 ± 41 kHz/%, and 647 ± 57 kHz/% at second, fourth, and sixth harmonic resonance, respectively.

Neural-Network-Based Automated Synthesis of Transformer Matching Circuits for RF Amplifier Design

Rich experience and intuition play important roles in designing planar transformers (TFs) for contemporary radio frequency integrated circuits (RFICs). In general, RFIC designers have been heavily relying on multiple iterations of full electromagnetic (EM) simulations, which consumes much time and effort. Here, we propose an automated matching circuit synthesizer (AMCS) using neural networks (NNs). The proposed AMCS directly synthesizes a matching circuit combined with a TF throughout the entire design process, ranging from the desired performance to layout. In the AMCS, which is a “spec-to-layout” synthesizer, one NN returns physical parameters of matching circuits, and another NN estimates the electrical performance in two-port <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S$ </tex-math></inline-formula> -parameters from the desired impedances. Before the NNs are trained, input feature design is conducted to avoid the one-to-many problem, which cannot be well characterized with an inverse NN. This significantly reduces the time and effort for iterative circuit and EM simulations. The AMCS generated the matching circuit layouts for simple single-stage amplifiers operating at different frequencies up to 70 GHz or in different bandwidths of up to 32.5%. The estimated <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S$ </tex-math></inline-formula> -parameters of the amplifiers show good agreement with the EM simulation results.

A 120–140-GHz LNA in 250-nm InP HBT

This letter presents a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$D$ </tex-math></inline-formula> -band low-noise amplifier (LNA) in 250-nm InP HBT technology for the next-generation wireless applications. The LNA has a measured peak gain of 13 dB, a 3-dB bandwidth greater than 20 GHz (120–140 GHz), and a measured noise figure (NF) of less than 6 dB in the band. A reduction in the 3-dB bandwidth from simulation was observed during the measurements which was attributed to the substrate waves using full chip electromagnetic (EM) simulation. EM simulations show that a partial or complete removal of the back side metallization of the InP substrate, holes in metal-1 ground plane, or a strategic placement of through-substrate vias suppress these substrate waves. To the authors’ knowledge, this is the first 120–140-GHz LNA in the InP 250-nm HBT technology.

Strong coupling of plasmonic waves in graphene for light confinement

The interplay between light and matter is highly required in many fundamental processes and optical devices. Herein, a hybrid graphene-based coupling system in the far-infrared range is proposed to investigate effective light confinement. In our system, the coupling of localized surface plasmons (LSPs) in graphene nanoribbons and Tamm surface plasmons (TSP) in a graphene sheet produces a hybrid dual-band absorption. This property is numerically verified by full electromagnetic simulations and analytically calculated by the rigorous coupled wave theory (RCWA). The hybrid nature of the two optical modes reflected by coupled oscillator model is discussed carefully, and the influences of incident angle and the geometric parameter on the coupling system are also analyzed. We have found that the coupling strength of the hybrid optical mode can be manipulated flexibly by the incident angle and the geometric parameter. Additionally, the group time delay of the light has also been considered, and calculated values as high as 114 ps. This work offers a new paradigm for tunable light-graphene interaction, and facilitates the design of slow light devices in the far-infrared spectral band.

Design and Fabrication of Millimeter-Wave Frequency-Tunable Metamaterial Absorber Using MEMS Cantilever Actuators.

In this paper, a MEMS (Micro Electro Mechanical Systems)-based frequency-tunable metamaterial absorber for millimeter-wave application was demonstrated. To achieve the resonant-frequency tunability of the absorber, the unit cell of the proposed metamaterial was designed to be a symmetric split-ring resonator with a stress-induced MEMS cantilever array having initial out-of-plane deflections, and the cantilevers were electrostatically actuated to generate a capacitance change. The dimensional parameters of the absorber were determined via impedance matching using a full electromagnetic simulation. The designed absorber was fabricated on a glass wafer with surface micromachining processes using a photoresist sacrificial layer and the oxygen-plasma-ashing process to release the cantilevers. The performance of the fabricated absorber was experimentally validated using a waveguide measurement setup. The absorption frequency shifted down according to the applied DC (direct current) bias voltage from 28 GHz in the initial off state to 25.5 GHz in the pull-down state with the applied voltage of 15 V. The measured reflection coefficients at those frequencies were −5.68 dB and −33.60 dB, corresponding to the peak absorptivity rates of 72.9 and 99.9%, respectively.

An electrostatic model of the cutoff probe

Although a circuit model of the previously developed cutoff probe for plasma diagnostics elucidates the basic physics and contributes to the development of the cutoff probe, a theoretical validation of the circuit model has yet to be accomplished. For theoretical validation, this paper proposes a one-dimensional electrostatic model, or 1dESM, of the cutoff probe, which is based on electrostatic field analysis in a finite two-wire approximation. The transmission spectrum S21 calculated by the 1dESM shows a good agreement with that from a three-dimensional full electromagnetic wave simulation for various electron densities and pressures. Based on the 1dESM, the formation mechanism of the S21 of the cutoff probe was analyzed. Theoretical validation of the circuit model was then achieved by comparing the circuit model with the 1dESM. This paper is believed to contribute to a better understanding of the cutoff probe and to the development of cutoff probe models.

Modeling the Optical System of NASA's EXCLAIM Mission

NASA's EXperiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM), is a balloon-borne instrument that is designed to perform intensity mapping of CO and CII at redshifts as high as z=3.5. It will map galaxy and star formation history over cosmological time. EXCLAIM will also demonstrate novel integrated silicon spectrometers using microwave kinetic inductance detectors (MKIDs) that could be an enabling technology for the Origins Space Telescope or other future mid- to far-infrared space telescopes. Here we present progress toward a full electromagnetic simulation of EXCLAIM's optical system at its operational frequencies. The goal of these simulations is to verify the design of the optical system meets mission requirements. When combined with measurements of the instrument, the simulation will also verify that our understanding of the optical system is complete. This work is being done in preparation for the first flight in mid 2022.

Electromagnetic Models for Passive Detection and Localization of Multiple Bodies

The paper proposes a multi-body electromagnetic (EM) model for the quantitative evaluation of the influence of multiple human bodies in the surroundings of a radio link. Modeling of human-induced fading is the key element for the development of real-time Device-Free (or passive) Localization (DFL) and body occupancy tracking systems based on the processing of the Received Signal Strength (RSS) data recorded by radio-frequency devices. The proposed physical-statistical model, is able to relate the RSS measurements to the position, size, orientation, and random movements of people located in the link area. This novel EM model is thus instrumental for crowd sensing, occupancy estimation and people counting applications for indoor and outdoor scenarios. The paper presents the complete framework for the generic N-body scenario where the proposed EM model is based on the knife-edge approach that is generalized here for multiple targets. The EM-equivalent size of each target is then optimized to reproduce the body-induced alterations of the free space radio propagation. The predicted results are then compared against the full EM simulations obtained with a commercially available simulator. Finally, experiments are carried out to confirm the validity the proposed model using IEEE 802.15.4-compliant industrial radio devices.

Calibration of the KIT test setup for the cooling tests of a gyrotron cavity full-size mock-up equipped with mini-channels

In high-power fusion gyrotrons, the maximum heat-load on the wall of the interaction section is in the order of 2 kW/cm2, which is the major limiting technological factor for output power and pulse-length of the tube. The ongoing gyrotron development demands a very effective cavity cooling system for optimum gyrotron operation. In this work, the experimental investigation of a mini-channel cavity cooling using a mock-up test set-up is described. The mock-up test set-up will be used to experimentally validate the predictive simulation results and verify the mini-channel cooling performance. It is crucial for validation of the mini-channel cooling properties to determine the amount of the heat load introduced in the cavity wall by an induction heater. In order to estimate that heat load, full 3D electromagnetic simulations have been performed using the CST Studio Suite® software. A suitable calibration factor for the load deposited in the mock-up inner wall is identified after numerical investigation by a 3D thermal model. Calorimetry measurements are performed and the experimental results are compared with the simulation results obtained with a 3D thermal-hydraulic model, using the commercial software STAR-CCM+. When the calibration factor is applied, the experimental calorimetry is well reproduced by the simulations.

One‐Pot Bio‐Assisted Synthesis of Stable Ag–AgCl System Using Jellyfish‐Based Scaffold for Plasmonic Photocatalysis Applications

AbstractPlasmonic assisted photocatalysis has emerged in the past decade as an efficient, high‐performance methodology. Such a system is often composed of the dispersal of noble metal nanoparticles on a semiconductor. In this architecture, the application of light at the plasmon frequency allows the separation of charge at the Schottky interface between the metal and the semiconductor, which can be further used for efficient catalysis. Here, a one‐pot green bio‐synthesis of Ag antibacterial nanoparticles attached to AgCl crystals while embedded in a jellyfish‐based eco‐friendly scaffold, is reported. The synthesis utilizes the chemical reduction properties of mucin protein found in the Jellyfish biomass, and thus the resulting Ag@AgCl system is firmly bound to the scaffold, making this membrane very stable. The system's photocatalytic activity is investigated by decomposing methyl orange and full electromagnetic simulations.

A Compact Diplexer Using Coupled π-CRLH Zeroth Resonators

ABSTRACT This paper presents a new diplexer design of a new-coupled composite right/left-handed (CRLH) resonator to serve the LTE applications. The realization of the diplexer is designed as coupled two zeroth order π-CRLH resonators to represent with zero electrical length and hence attaining a significant size reduction. The filters are designed to achieve a desired frequency bandwidth of 4% ∼16.7 Q-factor and ∼0.066 coupling coefficient at a centre frequency of 2.1 and 2.6 GHz with transmission zeros. The diplexer exhibits a rejection level of 15–20 dB while maintaining insertion loss of 1 dB for the Tx and Rx bands. The circuit design concepts are verified using equivalent circuit simulations, full electromagnetic simulations and experimental measurements. In conclusion, a good agreement is perceived between the measured and simulated data with size compactness of 30 × 60 mm2.

An E-Band 21-dB Variable-Gain Amplifier with 0.5-V Supply in 40-nm CMOS

This paper presents a variable-gain amplifier (VGA) in the 68–78 GHz range. To reduce DC power consumption, the drain voltage was set to 0.5 V with competitive performance in the gain and the noise figure. High-Q shunt capacitors were employed at the gate terminal of the core transistors to move input matching points for easy matching with a compact transformer. The four stages amplifier fabricated in 40-nm bulk complementary metal oxide semiconductor (CMOS) showed a peak gain of 24.5 dB at 71.3 GHz and 3‑dB bandwidth of more than 10 GHz in 68–78 GHz range with approximately 4.8-mW power consumption per stage. Gate-bias control of the second stage in which feedback capacitances were neutralized with cross-coupled capacitors allowed us to vary the gain by around 21 dB in the operating frequency band. The noise figure was estimated to be better than 5.9 dB in the operating frequency band from the full electromagnetic (EM) simulation.

부분 해석 결합 모델을 이용한 커넥터의 효율적 해석 방법

This paper presents a method for the efficient simulation and analysis of connector designs. Connectors used in a high-frequency system comprise various materials. Matching the impedance of the discontinuous part of the internal lines is difficult, owing to their complex structures. Therefore, it is essential to predict and modify the impedance discontinuity at the design stage. Moreover, the process of predicting the characteristics through electromagnetic (EM) simulations is essential to detect the deterioration in the performance of the connector installed in the system and the electromagnetic coupling between the boards. Therefore, the accuracy and time required for the simulations are important factors to be considered at the design stage of the connector. This paper proposes an assembled EM simulation method, which observes the scattering (S) parameter and time domain reflectometer impedance by performing transient analysis. To reduce the difference from the full EM simulation, the number of parts to be analyzed should be minimized. Thus, the full model is divided into connectors and peripheral systems to extract 8×8, 16×16, and 2×2 S-parameters of the Sub-Miniature version A connector, which is used for measurement. By comparing the results of the full EM simulation, the assembled EM simulation, and the measurement, the assembled EM simulation method proposed in this paper is validated.