A broadband circularly polarized patch antenna with suspended structure is proposed. The suspended patch has an indented edge and a gap-coupled feed. By optimizing the geometries of the antenna, a wide impedance bandwidth of 1.26-1.965 GHz and an axial ratio bandwidth of 1.51-1.68 GHz are obtained. The antenna with simple structure is simulated and measured, and the results show that the bandwidth of the patch antenna is successfully broadened by using the suspended configuration, indented edge and gap-coupled feed.

It is difficult to determine the feed radiation center and F/D of the reflector impulse-radiating antenna (IRA) in frequencydomain, due to its ultra-wideband (UWB) property. This paper presents an efficient approach to design the reflector IRAs, via evaluating the transient radiation patterns (TRPs) of the feed for some given different radiation centers. Only one time-domain simulation for the feed is needed in this method. Comparing with the global optimization algorithms, our method is fast and reliable in the design of the reflector IRAs.

The launching of high-frequency electromagnetic waves into fusion plasmas is an effective method for plasma heating and noninductive current drive. In addition, the reflection of electromagnetic waves on the plasma cutoffs is utilized in electron density diagnostic measurements. The scope of this article is to comment on the standard approximations made in the simulation of electron-cyclotron wave propagation and absorption in tokamak plasmas, in connection to the established modeling tools and the underlying physics, as well as to illustrate the limits of their validity, especially regarding the applicability to ITER-related studies and beyond. The identification of possible gaps in the current state-of-the-art and the implication of new requirements for theory and modeling are also discussed.

In this article, a fractal-based composite right/left-handed transmission line (TL) is proposed, and its applications in miniaturized negative-order resonant (NOR) antennas are investigated. The TL unit-cell is constructed by etching a Hilbert-fractal slot on the surface of a substrate integrated waveguide structure. The dispersion analysis shows that the proposed TL can be used to design miniaturized NOR antennas. Then, two fractal-based NOR antennas are designed and fabricated. According to the measured results, the electrical sizes of the fabricated open-ended and short-ended antennas are 75.8% and 74.6% smaller than those of the reported counterparts, respectively. In addition, compared with the microstrip patch antennas, the fabricated antennas exhibit similar gain level and radiation patterns, but have a much smaller electrical size.

In this paper a multisphere particle method is developed to estimate the solution of the Poisson's equation with Neumann boundary conditions describing the neuronal human brain activity. The partial differential equations governing the relationships between neural current sources and the data produced by neuroimaging technique, are able to compute the scalp potential and magnetic field distributions generated by the neural activity. A numerical approach is proposed with current dipoles as current sources and going on in the computation by avoiding the mesh construction. The current dipoles are into an homogeneous spherical domain modeling the head and the computational approach is extended to multilayered configuration with different conductivities. A good agreement of the numerical results is shown compared for the first time with the analytical ones.

The effect of human body on inkjet-printed flexible single-layer transmission lines in immediate proximity of body is investigated by simulations and measurements up to 9 GHz. A multliine extraction method is used to obtain effective material parameters allowing detailed analysis of body effects. Already at 1 mm distance from the body, the line properties converge toward the free-space values. However, at smaller distances and in direct contact with the body, often required in biosensor applications, there is a significant change in characteristic impedance and increase in losses. The results of the paper can be used to evaluate the body effects at different frequencies and at different small distances from the body.

Magnetic resonance imaging (MRI) is a well established non-invasive technique to retrieve structural information from plants and fruits. Water transport inside these materials has also been studied with MRI, however, the integrate combination of studying both structure and dynamics has hardly been considered. Here it is shown how the anisotropic nature of water diffusion in channels or vessels inside the plant, combined with plant structural information, can be used to map these vessels in three dimensions. Diffusion Tensor Imaging (DTI), an MR technique initially introduced to study white matter in mammalian brains, is used to track water transport pathways inside Thompson Seedless grapes and celery as an example.

The system which enhances wireless power transmission efficiency for bio-medical applications has been proposed in this report. The system that operates at giga-hertz ranges is based on an inductive coupling between a transmitter coil and a receiver coil. A magnetic current source was modeled to a magnetic dipole with magnetic dipole moment m. To increase wireless power transmission efficiency, a high surface impedance ground plane was used and reflection from the ground plane is responsible for constructive interference. For this system, a theoretical study has been performed in this report by solving Sommerfeld integrals. Compared with the result of a system without a ground plane, the system with a high surface impedance ground plane showed enhancement of received power at a given transmitted power.

Synthetic aperture radar (SAR) automatic target recognition (ATR) has been receiving more and more attention in the past two decades. But the problem of how to overcome SAR target ambiguities and azimuth angle variations has still left unsolved. In this paper, a multi-scale local phase quantization plus biomimetic pattern recognition (BPR) method is presented to solve these two difficuties. By applying multiple scales local phase quantization (LPQ) on the observed SAR images, the blur and azimuth invariant features can be extracted, and these features are fusion with consecutive multiple scales to achieve better results. Then PCA method is applied to further reduce the feature dimension and achieve its efficiency. Finally, high dimensional space geometry covering method based on BPR theory is adopted to construct hyper sausage neuron links for target recognition. Experiments on the MSTAR database show that the proposed method can achieve satisfying recognition accuracy compared with other state-of-the-art methods.

The electromagnetic characterization of piezoelectric micro-needle antenna sensors for fully non-invasive detection of cancer-related anomalies of the skin is presented. To this end, a full-wave finite-difference time-domain procedure is adopted to analyze the performance of the considered class of devices in terms of circuital characteristics and near-field radiation properties as a function of the curvature radius of the relevant sensing probe. This analysis is, in turn, useful to gain a physical insight into the processes which affect the behavior of the structure and, hence, the accuracy in the detection of possible malignant lesions of the skin. In particular, by using the mentioned modeling approach, an extensive parametric study is carried out to analyze the effect produced on the sensor response by variations of the complex permittivity of the skin due to the presence of anomalous cells and, in this way, obtain useful discrimination diagrams for the heuristic evaluation of the exposure level to the cancer risk.

The single mode condition of rectangular waveguides is derived by using a simple ray-optics approach, which relies on geometrical ray tracing principles as in classical optics. Light propagation through such a waveguide can be approximately simplified as reflections within two planes of incidence. By employing the mode equations for different polarizations, a relation that shows the single-mode cut-off as a function of the waveguide dimensions is readily obtained.

Vertical electric fields generated by lightning leader channels, the total leader field change and the total leader field change to the total return stroke field change ratio, at a certain distance, were theoretically analysed by varying the angle of orientation of a segment of upper part. Ground was treated as a perfectly conducting horizontal plane. Results were able to discern significantly large differences in the static field due to leader channels which have the same total length but a certain channel segment is oriented at different angles. The outcome of our calculations consistently explains the scatter of the total leader field observed in previous studies. Without considering such channel segment orientation, one has to assume unrealistic charge source heights or unreasonable charge densities to calculate matching values for many observed total leader fields and leader field to return stroke filed ratios, labelled as anomalous observations in the literature. In some cases, irrespective of the charge source height and the charge density, one cannot find a suitable fit for the observed fields with the straight channel model.

A compact dual-band antenna for WLAN applications and Long Term Evolution (LTE) services in the 800 MHz band is designed. The compactness, the robustness, and the simplicity of the proposed solution make it suitable for the integration in recent and widely diffused mobile and multi-standard devices. The multiband behavior is yielded by exploiting a Sierpinski Gasket fractal shape whose descriptors are perturbed by means of a particle swarm optimization (PSO) strategy to fit the performance requirements. The results assess the good matching between numerical simulations and experimental validations as well as the effectiveness of the prototype in reaching a suitable impedance matching and satisfactory radiation characteristics.

Current shielding effectiveness (SE) of electromagnetic shielding (EMS) fabric is tested in the plane state, the testing results are difficult to describe the shielding effect of a garment in a curve surface state after manufactured by the fabric. To solve this problem, this study proposes a new SE computation model of the EMS fabric based on a SE vector. The model can calculate a theoretical SE value of the EMS fabric in the curve surface state. A number of factors which determine the SE of the fabric with a curve surface are analyzed according to the principle of the reflection and transmission of the electromagnetic wave. This study also gives a new argument that the curve fabric can be divided into many micro-planes and the fabric SE is considered as a vector. And then a computation model of the SE of the curve fabric is constructed. The detail of computation is deduced, and an application example is given. Results of experiments and analyses show that the method is scientific and correct, and the error between the computation SE value and the testing SE value of the local garment is less than 3%. The model provides a new way to calculate the SE of the EMS fabric with symmetric curved surface.

A novel implementation of aggressive space mapping (ASM) for the automatic layout synthesis of planar metamaterial structures is outlined in this article. Specifically, we employ a model-trust region optimisation approach to significantly reduce the computational burden associated with the direct optimisation of high-fidelity models. A Visual Basic for application (VBA) link to a commercial full-wave electromagnetic (EM) solver is created, to ensure that the automated Matlab-based platform has complete control of the design and analysis of the entire ASM process. The validity and efficiency of our approach is demonstrated with examples of complementary split-ring resonator (CSRR)-loaded transmission lines, comparing both modified and unmodified version of the quasi-Newton iteration within the ASM framework.

An 8 mm-band passive millimeter-wave imager BHU-2D has been developed by Beihang University. This imager is designed for detecting concealed weapons on human body. The imager adopts two-dimensional synthetic aperture interferometric radiometer (SAIR) technique which avoids the radiation risk to human body. Compared with scanning technique, SAIR technique could obtain images of a larger field of view (FOV) while achieving high imaging rate, which are necessary for security monitoring. In this paper, the imaging principle of SAIR is stated firstly. Secondly, background cancellation method designed for BHU-2D is interpreted. The technique is used to reduce the complexity as well as the dimensional requirements of the receiving elements. Thirdly, system configuration is illustrated in detail. Then external point source calibration method is introduced and discussed specifically for security check applications. Finally, imaging experiments on a person with concealed weapon are conducted by which the design and image calibration algorithms are verified. To conclude, experimental results prove that BHU-2D could be employed in security check applications.

The magnetic energy and inductance of current distributions on the surface of a torus are considered. Specifically, we investigate the in°uence of the aspect ratio of the torus, and of the pitch angle for helical current densities, on the energy. We show that, for a fixed surface area of the torus, the energy experiences a minimum for a certain pitch angle. New analytical relationships are presented as well as a review of results scattered in the literature. Results for the ideally conducting torus, as well as for thin rings are given.

Compressive Sensing (CS) is a recently developed technique, which can reconstruct the sparse signal with an overwhelming probability, even though the signal is sampled at highly sub-Nyquist rate. Based on the observation that the electromagnetic scattering structure (ESS) of a metal landmine is composed of two scattering centers, whose geometrical parameters are tightly related to its physical dimensions, a new physics-based landmine discrimination approach is proposed in this paper. Firstly, the approach uses the Multi-Measurement Iterative Pixel Discrimination method to reconstruct the landmine's ESS in noisy environments. Secondly, the geometrical parameters of the landmine's ESS are extracted from the sparse image. Thirdly, landmine discrimination is conducted according to the measured geometrical features and apriori knowledge. Finally, the field experimental results demonstrate the effectiveness of the proposed approach.

The purpose of this paper is to investigate the use of simulation technology for the analysis of wireless propagation channel in medical environments. In this paper, the channel modeling has been carried out by using an effective simulation platform, which combines full-wave Method of Moments and adaptive ray tracing technique. Base on this, the channel characteristics involving both large-scale and small-scale parameters of a wireless network deployed within a hospital environment can be estimated. Also, it is straightforward to predict the levels of electromagnetic field interference produced from the network infrastructure. The simulated results of four scenarios of medical environment, such as the patient room, the operating room, a particular level of the hospital, and the cardiac stress test room, with different wireless technologies used show the advantage and capability of the presented simulation approach.

A vector network analyzer (VNA) with a bulk current injection (BCI) probe is proposed to measure the transmission coefficient of a PCB. The purpose of developing such a measurement techniques is to predict the radiated emission for good correlation with the fully-anechoic chamber measured results. In this study, the proposed method is used to determine the radiated emission from a DC supply loop. Moreover, the proposed method can be further used to accurately predict the reduction of radiated emission from the improved DC supply loop. Electromagnetic simulations is also developed to confirm the accuracy of the proposed techniques.