In this paper, several configurations of a rotary magnetic refrigerator are proposed and investigated using three dimensional finite element method simulations. Their electromagnetic performance is analyzed considering the magnetic flux density, the forces and the torque. The rotor is a single permanent magnet while the stator is made of four refrigerant beds and a magnetic yoke. Multipole stators or rotors with 4, 6 and 8 refrigerant beds have been tested. The beds can be fitted or set at the inner surface of the yoke. The yoke can have smooth or salient poles. To minimize the magnetic torque, an original structure is proposed and tested. It is composed of two half-systems assembled with a 45o angle shift between rotors or stators. Because of the large amount of data, a suitable procedure to achieve an effective comparison between all configurations is established.
An analytical solution for the scattering of an electromagnetic plane wave from a perfect electromagnetic conducting (PEMC) circular cylinder coated with chiral material is derived. The PEMC cylinder as well as coating layer is of infinite length (2-D problem). Parallel polarization of the plane wave is considered for the analysis. The response of the chiral coated geometry has been observed for DPS-chiral, DNG-chiral and chiral-nihility coating layers. Also the behavior of the monostatic echo width for DPS-chiral and DNG-chiral layers has been studied against the admittance parameter. Results of bistatic echo width for the PEMC, PEC and PMC core have been presented. Under special conditions our results are in a very good agreement with the published literature.
In this paper, a high-efficiency wireless energy transmission via magnetic resonance is experimentally implemented in a resonator with the various sizes of transmitting and receiving coils and the receiving coil having two shapes of rectangular and circular types. The transmission efficiency is analyzed by varying the transmission distance. The resonance between the transmitting and receiving coils is achieved with lumped capacitors terminating the coils. The transmission efficiency of the resonator consisting of a circular transmitting coil with a diameter of 60 cm and rectangular receiving coil with a one side length of 10 cm is about 80% at the transmission distance of 20 cm. The transmission efficiencies of the wireless energy transmission resonator consisting of a receiving coil with the size of iPhone4 are about 75% and 40% at the transmission distances of 20 cm and 50 cm.
Circular synthetic aperture radar (CSAR) is different from other usual SAR modes, e.g., Stripmap SAR or Spotlight SAR, which takes a circular path rather than a straight path. It can provide not only two-dimensional (2-D) high resolution images but also three-dimensional (3-D) information about the target. In this paper, 2-D CSAR imaging containing 3-D information about the target is discussed. Considering the limited bandwidth of radar system and the limited angular persistence of the reflector's scattering characteristic in a real scene, we combine the data extrapolation technique based on the autoregressive (AR) model with the non-coherent combination of the sub-aperture images based on the approximate Generalized Likelihood Ratio Test (GLRT) technique to get a 2-D CSAR image with resolution improved and with aspect-dependent reflectivity characteristics kept. The GTRI T-72 tank dataset is processed to test the algorithm.
Power microwave was adopted to heat asphalt mixes with carbonyl iron powder (CIP) by its microwave absorbing characteristics. The Arch reflectivity system was employed for reflectivity tests in the frequency range of 2.0~4.0 GHz, and road properties of the asphalt mixes with different heating techniques were studied. The results indicate that 30 mm thickness of the asphalt mixes with the ratio of CIP absorber to asphalt 0.1 : 1.5, can effectively absorb microwave with a -19.1 dB absorbing peak at 2.45 GHz frequency. Microwave heating rate for asphalt mixes with CIP is 16 times higher than that for ordinary asphalt mixes. Microwave heating can enhance road properties of the asphalt mixes, such as Marshall stability, flow value, dynamic stability and splitting strength at low temperature to a certain extant when the ratio of CIP absorber to asphalt is from 0.1 : 1.5 to 0.3 : 1.5.
Existing focusing techniques for Ground Penetrating Radar (GPR) rely on migration of 2D or 3D images to remove clutter originating from objects laterally offset from the antenna. In applications requiring real-time focusing, a method operating on 1D trace data is required. This paper presents a new algorithm for focusing GPR images, the Vertical Offset Filter (VOF), using simulated and real GPR data.
This work presents a light-weight microwave system for the search and rescue of victims trapped under the rubble of collapsed building during an earthquake or other disasters. The proposed system based on a continuous wave X-band radar is able to detect respiratory and heart fluctuations: the information is extracted from the backscattered electromagnetic field exploiting independent component analysis (ICA) algorithm which provides an efficient noise and clutter cleaning. The proposed rescue radar is compact enough to be mounted onboard of a small unmanned aerial vehicle (UAV) in order to reach inaccessible or dangerous areas. The obtained experimental results show that the proposed detection method is able to successfully locate trapped victims with a reasonable degree of accuracy.
This paper demonstrates a novel and superior approach to enhance the incident angle based spectrum tuning capability of 1D ternary Photonic Band Gap (PBG) structure. The incidence angle sensitive wavelength band shift of a ternary periodic structure was significantly enhanced when the refractive index of sandwiched layers in each period was changed to 1.5 from 2.04. The ranges of enhancements for TE and TM wavelength band shifts were 0.5-1.5 nm and 5.5-20.5 nm respectively at different angles of incidence of light on the structure. Unlike previous approach, this approach not only enhances the incidence angle based spectrum tuning capability of 1D ternary PBG structure, but, it also ensures that the size of structure does not increase and temperature immunity of the structure does not decrease to enhance spectrum tuning capability.
The goal of this paper is to use defected ground structure (DGS) in microstrip antennas for dual band operation at microwave frequencies. The soft nature of the DGS facilitates improvement in the performance of microstrip antennas. A design study on microstrip patch antenna with specific DGS slot has been presented in the proposed work. In this paper, a stacked microstrip patch antenna (SMPA) has been designed for broadband behavior, and then skew-F shaped DGS has been integrated with a detailed study of possible DGS slots in a small area for dual band operation. The design and optimization of both the SMPA and DGS structures along with the parametric study were carried out using CST Microwave Studio V.9. Further, the dual band antenna, i.e., the SMPA with skew-F shaped DGS, has been fabricated, and the experimental results have shown a good agreement with the simulation ones.
Core loss data are usually provided in the form of tables or curves of total loss versus flux density or frequency for electrical machine designers. These tables or curves can be used to extract the loss coefficients of the core loss formulas because accurate calculations of the coefficients have an important issue in electrical machine design. In this study, using original loss data given for M19 steel material, the core loss coefficients are calculated by the genetic algorithm developed in Matlab environment and electromagnetic analysis software (Ansoft Maxwell) is also used to extract the core loss coefficients in order to verify the proposed method. It is found that the exponent of flux density (B) depends on the flux range or the frequency range and these changes in the exponent of B can be correlated to the physical phenomenon of domain wall movement in response to an external field. As a difference from existing studies in literature, this study suggests a new method for extracting the core loss coefficients without any requirement for mathematical operations due to the nature of genetic algorithms and over the range of frequencies between 50-400 Hz and flux densities from 0 to 1.5 T, the new method yields lower errors for the specific core losses than those obtained by the magnetic field analysis software.
Human body interaction is an important issue to take into account when designing handset antennas due to the effect that it has on the electromagnetic performance of the antenna. By means of electromagnetic simulation, three different antennas (a 1-meter length monopole and two small handset antennas) in three different situations (free-space, hand holding, and in pocket position) have been analysed at the FM band (88 MHz-108 MHz). Results prove that it is possible to predict the antenna behaviour in terms of quality factor (Q) by assessing the variations of the near electric field and the radiation efficiency in said environments. The estimated Q can be verified by calculating the Q using the input impedance. Results show that human body may improve the efficiency when the antennas become an extension of the human body.
To accurately model nanophotonic structures, a conformal dispersive finite difference time domain (FDTD) method based on an effective permittivity technique is presented, which can describe exactly the behaviors of evanescent waves in the vicinity of curved interface. A mismatch between the numerical permittivity and the analytical value introduced by the discretization in FDTD is demonstrated, thus, very fine time-step size is always necessary for nanostructures modelling, which greatly increases the required overheads of CPU time as compared to usual FDTD simulations. To resolve this problem, the performance of parallel FDTD code is investigated on a Gigabit Ethernet, and the acceleration technique for parallel FDTD algorithm is presented, which is developed by means of the replicating computation based on overlapping grids, the OpenMP multithreading technique and the vectorization based on SSE instruction. The comparison of relevant numerical results shows that these methods are able to reduce the expense of the system communications and enhance the utilization ratio of the CPU effectively, which improves greatly the performance of parallel FDTD with high time-consuming.
A new three dimensional conical ground plane electromagnetic cloak is proposed and designed based on the coordinate transformation of Maxwell's equations. Material parameters of the conical invisible cloak are derived which have simple form and lesser inhomogeneity compared with other 3-dimensional cloaks. Because of convenient form of the constitutive tensors of the conical cloak, we propose a new strategy for homogeneous approximation of the materials of the cloaks. Numerical simulations confirm that approximation with eight slices, is more than enough and this cloak can hide any object on the ground as well as inhomogeneous ones.
The simulation of nonlinear loaded high-speed microstrip interconnects by means of a convolution-based procedure is described when both, analytical and measured scattering parameters are used. Closed-form equations are employed to obtain the analytical scattering parameters. The influence of measured scattering parameters, when these are used instead the analytical ones, is investigated to know how the microstrip interconnect responses are affected. The convolution procedure is complemented by including the transmission line linear equation and the microwave circuit reflection theory. S
Three distinctively different implementations of convolutional perfectly matched layer for the FDTD method on CUDA enabled graphics processing units are presented. All implementations store additional variables only inside the convolutional perfectly matched layers, and the computational speeds scale according to the thickness of these layers. The merits of the different approaches are discussed, and a comparison of computational performance is made using complex real-life benchmarks.
The aim of the paper is to present a simple but well applicable development, to generate the waveform of the magnetic flux density, and so the magnetic hysteresis, for any signal frequency. The proposed approach is based on the knowledge of the signal spectrum for one given frequency. It allows to construct the spectrum for any other frequency. Then, the constructed signal is transformed back to the time domain.
During the last two decades, several simulation tools have been proposed for the modeling of electronic equipments in function of the physical environmental changes. It was stated that numerous electronic components such as semiconductor devices can be affected by the mechanistic effects, humidity or simply the temperature variations. To study the last effect, based on the multilayer perceptron neural network (MLPNN), a characterization method of the passive electronic device thermal effects is introduced in this paper. The method proposed was realized toward the equivalent circuit identification of the under test device (R, L, C components) measured input impedances. To demonstrate the relevance of the method, numerical computations with MLPNN algorithms implemented into Matlab were performed. First, a capacitor modeling from 30 kHz to 1 GHz for the temperature variation from 25°C to 130°C is presented. It was found that a good agreement between the proposed model and the measurement is observed. Then, a commercial EMI low-pass filter was also characterized in RF frequencies through the S-parameter identification. Finally, further discussion on the potential applications of this work, in particular, in the electromagnetic compatibility (EMC) field is offered in the last part of this paper.
The paper presents an approach to locate and concentrate electromagnetic energy on targets based on time delays. An array of antennas is used in the approach, in which one antenna sends ultra-wide-band signals, and all antennas receive the signals backscattered by the targets. The time delays can be obtained by the interrelation of the transmitted and received signals. By controlling the timing of the pulses radiated from the individual antennas, high concentration of electromagnetic energy on the targets' locations can be achieved. The performance of this approach is demonstrated by several numerical simulations.
This paper introduces an imaging algorithm with application of fractional Fourier transform (FrFT) for ground moving train imaging by Ku-band ground-based radar. In view of the fact that the train speed is varying when acrossing the radar beam, the multiple Doppler parameters are estimated corresponding to different range positions, i.e., they are estimated from different sections of data in FrFT domain, then the train is imaged section by section, and finally these sectional images are combined to get the full image of the train. Because traditional parameter estimation method by two-dimensionally searching the peaks in FrFT domain is inefficient, we transfer the parameter searching problem into an one-dimensional optimization problem, which can be solved with high efficiency by using the golden section searching method.
In this paper, we introduce a dispersion equation for 3D photonic crystals made of parallel layers of non-overlapping spheres, valid when both wavelength and separation between layers are much larger than the distance between neighbouring spheres. This equation is based on the Korringa-Kohn-Rostoker (KKR) wave calculation method developed by Stefanou et al.~and can be used to predict the spectral positions of bandgaps in structures made of dispersive spheres. Perfect agreement between the spectral positions of bandgaps predicted with our simplified equation and those obtained with the numerical code MULTEM2 was observed. We find that this simplified relation allows us to identify two types of bandgaps: those related to the constitutive parameters of the spheres and those related to the three dimensional periodicity (distance between layers). Bandgaps of the first type are independent of the frequency and the distance between layers, while those of the second type depend only on these two quantities. We then analyze the influence of the constitutive parameters of the spheres on the spectral position of bandgaps for spheres immersed in dielectric or magnetic homogeneous media. The number and positions of the bandgaps are affected by the permitivity (permeability) of the host medium if the spheres have dispersive permitivity (permeability).