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In this paper, we propose a novel method to treat thin conductive (TC) sheets of arbitrary three-dimensional (3-D) shape and curvature with the electromagnetic (EM) finite-difference time-domain (FDTD) algorithm without the need to resolve the sheet thickness spatially. We show that the physical properties of TC sheets enable us to do so without introducing additional field components to the conventional Yee scheme. Due to this noninvasive approach, in addition to the preserved stability of the FDTD algorithm, the method can be directly applied to any existing FDTD kernel, such as parallelized or hardware accelerated versions. The method has been developed within the framework of a professional EM FDTD software package and tested on real-world problems. Index Terms--Coatings, electromagnetic (EM) compatibility, finite-difference time-domain (FDTD) methods, metals, modeling, numerical analysis, simulation, software, thin films.

In this paper, we describe a specifically designed patch antenna that can be used as the basis antenna element of a clinical phased-array head and neck hyperthermia applicator. Using electromagnetic simulations we optimized the dimensions of a probe-fed patch antenna design for operation at 433 MHz. By several optimization steps we could converge to a theoretical reflection of -38 dB and a bandwidth (-15 dB) of 20 MHz (4.6%). Theoretically, the electrical performance of the antenna was satisfactory over a temperature range of 15[degrees]C-35[degrees]C, and stable for patient-antenna distances to as low as 4 cm. In an experimental cylindrical setup using six elements of the final patch design, we measured the impedance characteristics of the antenna 1) to establish its performance in the applicator and 2) to validate the simulations. For this experimental setup we simulated and measured comparable values: -21 dB reflection at 433 MHz and a bandwidth of 18.5 MHz. On the basis of this study, we anticipate good central interference of the fields of multiple antennas and conclude that this patch antenna design is very suitable for the clinical antenna array. In future research we will verify the electrical performance in a prototype applicator. Index Terms--Antenna design, FDTD model, hyperthermia, patch antenna.

A new conformal finite-difference time-domain (CFDTD) updating scheme for metallic surfaces nonaligned in the grid is presented in this paper. In contrast to existing conformal models, the new model can be formulated with the original Yee FDTD update equation. Therefore, the proposed scheme can be easily added in standard FDTD codes even if the codes are already parallelized or hardware-accelerated. In addition, based on the commonly used conventional stability criterion, a derivation of the stability is presented and based on the conformal geometric information, a time step reduction formula is presented. The time step reduction is used as a user-defined parameter to tradeoff speed versus accuracy. The achievable geometric precision is optimized to a given time step. Therefore, even with the conventional time step (no reduction) the presented scheme profits from the conformal discretization. To show the performance and the robustness of the proposed scheme canonical validations and two real world applications were investigated. A broadband low profile (circular) antenna was successfully simulated showing the benefit of the conformal FDTD method compared to the conventional scheme. Furthermore, a CAD based mobile phone was conformally discretized and successfully simulated showing that the proposed scheme is highly suited for the simulation of advanced engineering problems. Index Terms--Conformal finite-difference time-domain (CFDTD) method, finite-difference time-domain (FDTD) method, subcell.

In this paper, a novel three-dimensional (3-D) sub-cell algorithm for modeling metallic objects which are nonconformally oriented within the finite-difference time-domain (FDTD) grid is proposed. The generally applicable algorithm is based on the contour-path (CP) technique and enables, in combination with an enhanced nonconformally aligned source model, a more accurate spatial representation of antenna structures than the common staircase approach. To evaluate the performance of the new algorithm, the simulation results are compared with the classical staircase approach for dipole antennas as well as for a generic phone. Signifcant improvements were achieved for all antenna parameters from the near and far field, i.e., feedpoint impedance, radiation pattern, and field distributions. Index Terms--Algorithms, antennas, finite-difference time-domain (FDTD) methods, simulation.

SUMMARY The evolution of processors into multi-core architectures has led to the acceleration of scientific codes using numerous highly specialized processors, that is, multi-core central processing units (CPUs), graphics processing units (GPUs) and also devices that merge both technologies in a single-die chip. Development of parallel codes that are both scalable and portable between the processor architectures is challenging. To overcome this limitation, we investigated the acceleration of the finite-difference time-domain (FDTD) method in computational electromagnetics on modern computing architectures, that is, multi-core CPUs and GPUs, through the use of Open Computing Language (OpenCL). Further extension of the OpenCL parallel programing model with the Message Passing Interface allows for the targeting of standard distributed memory computer clusters as well as clusters accelerated by GPUs. Portability between hardware manufactured by different vendors and highly specialized and parallel computing architectures is the main advantage of the developed FDTD solvers. The codes were coupled with a commercial simulation platform to evaluate the performance of the solvers in real-world industrial scenarios. Although the portability resulted in a slightly reduced performance (10-35%) of the OpenCL-accelerated FDTD simulations compared with the native Compute Unified Device Architecture or Open Multiprocessing implementations, the obtained benchmarking results of the OpenCL FDTD solvers on distributed memory systems show that the communication overhead can be hidden by computations for sufficiently large simulation domains with a scaling efficiency higher than 90%. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

With the continuous trend to smaller mobile devices with more functionality and more wireless bands, the possible insufficient over-the-air (OTA) performance becomes a growing concern for service providers. In addition to reduced radiation efficiency by smaller antennas in smaller phones, the head and in particular the hand may further impair radiation performance. The aim of this paper is to investigate the influence of the various parameters of the hand upon the OTA performance criteria to support the standardization process of the hand phantom and to provide the tools for optimization of handheld transmitters. The results reveal the following order of significance for small variations in hand parameters: 1) position of index finger; 2) distance between phone case and palm; 3) position of the other fingers; 4) size of the hand; 5) dielectric parameters; 6) wrist length and tilt. Some configurations may lead to a slight increase of the peak spatial SAR in the head. OTA assessment without the hand does not provide a good measure of phone performance in real life. However, good reproducibility of evaluations requires a precise definition of the hand, in particular its geometry and the phone position within the hand. [ABSTRACT FROM AUTHOR]

A commercial clam shell phone CAD model is used to numerically investigate the effect of a hand phantom on mobile phone antenna radiation performance. The simulation results show that the grip of the hand phantom is the most important parameter to antenna performance. The antenna is converted into a parameterized form, then optimized to achieve the targeted multi-band performance in real-usage conditions. [ABSTRACT FROM AUTHOR]

Discusses the general suitability and possible limitations of an enhanced finite-difference time-domain simulation environment for efficient radio-frequency design of complex transmitters. Use of multiband mobile phones; Conduction of simulations in free space and dielectric loads; Evaluation of impedance, efficiency, distribution of far-field and near fields and absorption rates; Electromagnetic field behavior prediction.

For quality assurance of hyperthermia treatment planning systems, quantitative validation of the electromagnetic model of an applicator is essential. The objective of this study was to validate a finite-difference time-domain (FDTD) model implementation of the Lucite cone applicator (LCA) for superficial hyperthermia. The validation involved (i) the assessment of the match between the predicted and measured 3D specific absorption rate (SAR) distribution, and (ii) the assessment of the ratio between model power and real-world power. The 3D SAR distribution of seven LCAs was scanned in a phantom bath using the DASY4 dosimetric measurement system. The same set-up was modelled in SEMCAD X. The match between the predicted and the measured SAR distribution was quantified with the gamma method, which combines distance-to-agreement and dose difference criteria. Good quantitative agreement was observed: more than 95% of the measurement points met the acceptance criteria 2 mm/2% for all applicators. The ratio between measured and predicted power absorption ranged from 0.75 to 0.92 (mean 0.85). This study shows that quantitative validation of hyperthermia applicator models is feasible and is worth considering as a part of hyperthermia quality assurance procedures.