XFdtd References

The following is a list of scientific and technical articles in which Remcom's software was used in the authors' research.  We've included excerpts from the publication abstracts and offsite links to the original published content.

1. Optimization and simulation of a 16-channel loop and dipole array for head MRI applications at 10.5 Tesla 

A sixteen-channel array consisting of eight pairs of stacked loop and dipole antennas was simulated for head MRI applications at 10.5 Tesla. Remcom XFdtd was used to calculate isolation between loop and dipole elements modeled with a dielectric load with varying space between loop and dipole elements. A loop-dipole array assembly was simulated for a candidate element configuration with a head-shaped dielectric phantom.

2. A simplified model for designing whip antenna mounted on a motorcycle

When we drive a car, the external antenna is electrostatically shielded by the car's body from the passengers. No such shield exists when we ride a motorcycle, and so the rider can affect the characteristics of the antenna mounted on the motorcycle. Therefore, the interaction between the antenna and the human body must be considered. This paper proposes a simple model to analyze the influence of the rider's body on the motorcycle's antenna. The radiation characteristics in the 145 MHz band and the impact of mounting position on the reflection coefficient are simulated using XFdtd software. The resulting values are compared with measured values.

3. High performance MIMO antenna for 5G wearable devices

In this paper, a dual-band 2×2 MIMO antenna for wearable device applications is presented to support the 5G radio frequency allocations at 3.3-3.6 and 4.5-5 GHz in China. The single antenna unit is composed of a monopole mode and a folded loop mode with a single feed to cover these two bands. Two identical antennas positioned at top and bottom sides of a smart watch-sized PCB (40×40mm2) are used to demonstrate the MIMO performance. The simulation results from XFdtd show that these MIMO antennas can achieve over 85 % efficiency, more than 17 dB isolation and 0.02 correlation coefficient at both bands.

4. Computational assessment of radiofrequency energy absorption of fetus during an MRI scan

This study presents a systematic analysis of specific energy absorption rate (SAR) in computational models of a pregnant woman and the fetus at three different gestation ages (3rd, 6th, and 9th month). Numerical simulations were performed at two frequencies (i.e., 64 and 128 MHz), for two coil diameters (i.e., 750 and 650 mm), and for seven landmarks, namely shoulder, heart, sternum, abdomen (i.e., fetus head), pelvis (i.e., fetus body), thigh, and knee. The effect of additional features on the SAR, such as input source locations and y-position of the pregnant woman model in the birdcage coil was evaluated.

5. Proton-decoupled carbon magnetic resonance spectroscopy in human calf muscles at 7 T using a multi-channel radiofrequency coil

C magnetic resonance spectroscopy is a viable, non-invasive method to study cell metabolism in skeletal muscles. This paper presents the development, evaluation, and first in vivo measurement with a 7 T 3-channel C and 4-channel H transceiver array optimized for H-decoupled C-MRS in the posterior human calf muscles. The developed coil array was successfully tested in phantom and in vivo MR experiments, showing a simplified spectral pattern and increase in signal-to-noise ratio of approximately a factor 2 between non-decoupled and H-decoupled spectra in a glucose phantom and the human calf muscle.

6. Evaluation of Propagation Characteristics Using the Human Body as an Antenna

In this paper, an inhomogeneous human body model was presented to investigate the propagation characteristics when the human body was used as an antenna to achieve signal transmission. Specifically, the channel gain of four scenarios, namely, (1) both TX electrode and RX electrode were placed in the air, (2) TX electrode was attached on the human body, and RX electrode was placed in the air, (3) TX electrode was placed in the air, and RX electrode was attached on the human body, (4) both the TX electrode and RX electrode were attached on the human body, were studied through numerical simulation in the frequency range 1 MHz to 90 MHz.

7. Improved reflector backed UWB fat monopole antenna for GPR application

Short range radar like ground penetrating radar needs large bandwidth for high resolution and low frequency for better penetration. This puts constraints on the antenna design to have a compact UWB antenna at lower center frequency with unidirectional pattern. This paper emphasizes on the improvement of fractional bandwidth of a stepped reflector backed fat monopole antenna for unidirectional radiation pattern throughout the required bandwidth. The design, simulation and experimental results are included in this paper.

8. Assessing the Electromagnetic Fields Generated by a Radiofrequency MRI Body Coil at 64 MHz: Defeaturing vs. Accuracy

This study aims at a systematic assessment of five computational models of a birdcage coil for magnetic resonance imaging (MRI) with respect to accuracy and computational cost. The accuracy of the models was evaluated using the “symmetric mean absolute percentage error” (“SMAPE”), by comparison with measurements in terms of frequency response, as well as electric (||E⃗||) and magnetic (||B⃗||) field magnitude. Significance: Computational modeling of birdcage body coils is extensively used in the evaluation of radiofrequency-induced heating during MRI. Experimental validation of numerical models is needed to determine if a model is an accurate representation of a physical coil.

9. A Novel Method for Separating and Locating Multiple Partial Discharge Sources in a Substation

In this paper, a novel method is proposed to improve the separation rate and the localization accuracy. A directional measuring platform is built using two directional antennas. The time delay (TD) of the signals captured by the antennas is calculated, and TD sequences are obtained by rotating the platform at different angles. The sequences are separated with the TD distribution feature, and the directions of the multi-PD sources are calculated. The PD sources are located by directions using the error probability method. To verify the method, a simulated model with three PD sources was established by XFdtd.

10. Investigation of coil designs for transcranial magnetic stimulation on realistic head model

This paper shows simulation results of transcranial magnetic stimulation (TMS) for three different coils including Fo8 (figure of eight) coil, V-shape coil, and butterfly coil. Considering the clinical applications the feasibility of three different coils in TMS is analyzed. XFdtd is used to obtain three dimensional distribution of electric field, magnetic field in the realistic head model. This study conducting with realistic head model offers actual penetration depth, focality, and biocompatibility which are not possible with homogeneous head model used in some existing works.

11. A Wideband Circularly Polarized Conformal Endoscopic Antenna System for High-Speed Data Transfer

In this paper, a conformal wideband circularly polarized (CP) antenna is presented for endoscopic capsule application over the 915-MHz Industrial, Scientific, and Medical (902-928 MHz) band. The thickness of the antenna is only 0.2 mm, which can be wrapped inside a capsule's inner wall. A single-layer homogeneous muscle phantom box is used for the initial design and optimization with parametric studies. The effect of the internal components inside a capsule is discussed in analyzing the antenna's performance and to realize a more practical scenario. In addition, a realistic human body model in a Remcom XFdtd simulation environment is considered to evaluate the antenna characteristics and CP purity, and to specify the specific absorption rate limit in different organs along the gastrointestinal tract.

12. Intercomparision of Performance of RF Coil Geometries for High Field Mouse Cardiac MRI

Multi-turn spiral surface coils are constructed in flat and cylindrical arrangements and used for high field (7.1 T) mouse cardiac MRI. The commercially available birdcage outperforms the cylindrical spiral coil in rSNR by a factor of 3–5 times. The comprehensive approach and methodology adopted to accurately design, simulate, implement, and test radiofrequency coils of any geometry and type, under any loading conditions, can be generalized for any application of high field mouse cardiac MRI.