The paper is devoted to the investigation of electromagnetic field distribution in the vicinity of overhead transmission lines under different environmental conditions, taking into account the wire sag curve in a span. A wire state equation is utilized, which allows one to calculate stresses in the wire and sags based on the known stresses and temperatures in the initial state. The results of the electric and magnetic field distribution on sample 330 kV and 110 kV transmission lines are presented. We show that the highest electromagnetic field levels are associated with the most severe environmental conditions, resulting in the highest sag.

In this paper, a liquid-core photonic crystal fiber (LCPCF) with small hollow-core filled by chalcogenide material CS₂ is designed. The supercontinuum (SC) generation in such a LCPCF with nonlinear coefficient of 3327 W^-1•km^-1 at 1550 nm and wide normal dispersion regime spanning from 1200 to 2500 nm is numerically studied by solving the generalized nonlinear Schrödinger equation. The influences of the pump pulse parameters on the SC spectral width and coherence are demonstrated, and the optimum pump condition for the SC generation is determined. Our study work can provide an alternative way for obtaining highly coherent SC, which is important for the applications in optical coherence tomography, frequency combs, and ultrashort pulse generation.

Recent wearable health monitoring systems use multiple biosensors embedded within a wireless device. In order to reliably transmit the desired vital signs in such systems, a new set of antenna design requirements arise. In this paper, we present a flexible, ultra-low profile, and compact dual band antenna. The proposed design is suitable for wearable and flexible telemedicine systems and wireless body area networks (WBANs). The antenna is inkjet printed on a 50.8 μm Polyimide Kapton substrate and fed by a Coplanar Waveguide (CPW). The proposed design has the merits of compactness, light weight, wide bandwidth, high efficiency, and mechanical stability. The performance of the antenna is also characterized against bending and rolling effects to assess its behavior in a realistic setup since it is expected to be rolled on curved surfaces when operated. The antenna is shown to exhibit very low susceptibility to performance degradation when tested against bending effects. Good radiation characteristics, reduced fabrication complexity, cost effectiveness, and excellent physical properties suggest that the proposed design is a feasible candidate for the targeted application.

A magneto-electric dipole antenna with novel feed design with rectangular cavity is proposed, fabricated and analyzed. Due to this new feeding structure, the antenna has been able to achieve wide impedance bandwidth of 68.8% to accommodate various wireless communication applications. The stable peak gain of 10.45 dBi with unidirectional radiation pattern has also been reported for the entire range of operation. The antenna has also been able to achieve low cross polarization levels lower than -30 dB. The antenna exhibits low side lobe radiations and almost identical E plane and H plane radiation patterns in the operating frequency range of 2.0 GHz-4.1 GHz. Due to its good electrical characteristics, the antenna is suitable for various S-band wireless communication applications.

A patch antenna integrated on the cover glass of a commercial space-certified solar cell is examined. Test fixtures were fabricated to study the antenna designed at 4.9 GHz when there was an active solar cell under the antenna. It is found that the solar cell affects the input impedance of the antenna and causes a 2-3 dB gain reduction. Repetitive tests were performed to confirm that the effect from solar cells on the antenna remained the same regardless of the working status of the solar cell, type of cover glass, or the assembly of the solar panel.

In this paper, we present a new computationally efficient method for direction-of-arrival (DOA) estimation in uniform linear arrays (ULAs). A sparse uniform linear array (SULA) structure is firstly extracted from the conventional ULA to exploit its advantage in high resolution. By performing the multiple signal classification (MUSIC), the noise subspace of the SULA is simultaneously orthogonal to the steering vectors corresponding to the true DOAs and several virtual DOAs, where all the true and virtual DOAs for each source are uniformly distributed in the sine domain. Then we divide the total angular field into several small sectors and search over an arbitrary sector. Finally, the true DOAs can be distinguished by the noise subspace of the original ULA. Since the proposed method involves a limited spectral search and a reduced-dimension noise subspace, hence it is quite computationally efficient. Simulation results are provided to verify the effectiveness of the proposed method in terms of computational complexity, estimation accuracy, and resolution performance.

By combining a horizontal bowtie electric dipole and a vertical rhombic loop antenna which is realized by a pair of folded shorted patches, a very wideband dipole-loop composite patch antenna is designed. Four tuning stubs are attached to the edges of the bowtie dipole to improve the impedance matching. The bowtie dipole and the rhombic loop antenna are excited simultaneously by a simple feed structure which not only forms a folded balun but also makes the antenna itself be direct current grounded. Results show that a wide impedance bandwidth of 121.6% for |S₁₁|<-10 dB from 3.5 to 14.35 GHz is obtained. Good radiation patterns, low back radiation, low cross polarization level, and a peak antenna gain of 7.7 to 9.8 dBi are achieved over the operating bands.

Recently, the RF/microwave electronic technology evolved with the consideration of plastic and organic substrates. Such a technology offers two-folded benefits: in one side for lowering the fabrication cost and in another side for the possibility to bend electronic devices. Such a technology is particularly interesting for the implementation of antenna system. This paper is dealing with the design of flexible microstrip antenna 1:2 array. Theoretical approach on the typically symmetrical antenna 1:2 array is proposed. The design methodology of microstrip antenna combined with 1:2 T-power divider (T-PWD) is described. Based on the transmission line theory, the S-parameter model of the antenna system with non-standard reference load is established. Then, the microstrip antenna passive system is theoretical analysed in function of the physical dimensions of the designed structure. The feasibility of the flexible antenna passive system is investigated with the proof-of-concept (POC) designed on Kapton substrate. The POC prototype consisted of microstrip antenna 1:2 array is designed to operate at about 5.8 GHz. Comparisons between the full wave simulated and measured return losses were performed. Then, simulated radiation pattern highlights the efficiency of the fabricated prototype of passive antenna array.

A metamaterial-based broadband antenna loaded with artificial impedance surface (AIS) is presented in this letter. Two metallic vias connect a Y-shaped patch to the ground plane. The patch, two metallic vias, and the AIS compose an epsilon negative (ENG) transmission line (TL). The asymmetry Y shaped patch and the AIS bring about the first-order resonance (FOR) and second-order resonance (SOR) modes, which can be merged into one passband to yield a wideband property. The proposed ENG-TL resonant antenna has the advantages of compact size, wide bandwidth, and high gain, which can be applied to portable and handheld communication system.

Thermal hose is capable of transferring the thermal energy of a finite source to arbitrary long distance. This is achieved by using stretching transformation and can be ideally constructed by using a material with a highly anisotropic thermal conductivity. For practical realization, such a thermal hose can be made of homogeneous conductors in bilayer configurations, employing only copper and expanded polystyrene. It is shown that the thermal energy can be well confined and almost perfectly transferred in an arbitrarily bending hose, demonstrating excellent flexibility. More interestingly is that, when a point heat source is placed at the opening of a split-ring-shaped hose, the temperature of the inner region becomes uniform and reaches nearly as high as the heat source. These novel properties of the proposed flexible thermal hose have been numerically validated in time-dependent case, showing excellent transfer and configuration of thermal energy.

Earlier studies have shown that the occupational exposure of electric fields at 400 kV substations can be higher than the low action level of 10 kV/m set by the Directive 2013/35/EU. One possibility for decreasing the occupational exposure is to surround the worker with a Faraday cage. The objective of the study was to investigate how effective a Faraday cage is in decreasing the ELF electric field exposure during work tasks from a man hoist at a 400 kV substation. First, we measured the electric field exposure while performing maintenance tasks from a man hoist. We then constructed a Faraday cage around the man hoist and measured the exposure again, with hopes that the exposure would be sufficiently reduced to create a safe working environment. The Faraday cage was constructed from a steel net 0.5 m in width with 19-mm meshes. The net was made of hotdip galvanized steel wire, 1.0 mm in diameter. The net and the man hoist were then grounded. The maximum electric field without the cage was 28.8 kV/m, and with the cage, it was 0.5 kV/m. The electric field, therefore, was decreased by 96.8-99.9%, validating the efficacy of Faraday cages.

Transient field of a high-altitude electromagnetic pulse (HEMP) induced near ground is simulated, of which the ground reflection can not be neglected. The Jefimenko's equation is applied to compute the incident electric field near the ground, attributed to both the primary and the secondary currents in the source region. The field-dependent air conductivity in the source region is obtained by solving three nonlinear governing equations iteratively, and the reflected field is computed in the frequency domain.

Planar gigahertz (GHz) inductors were fabricated based on high crystalline-anisotropy Zn_0.13Co_0.04Ni_0.63Fe_2.2O₄ (Zn-Co-Ni ferrite) and Ba₃Co₂Fe₂₄O₄₁ (Co₂Z hexaferrite) and characterized for inductance (L) and quality (Q) factor. The planar ferrite inductors show an L of 4.5 nH (Zn-Co-Ni), 5.6 nH (Zn-Co-Ni + low Hk and fFMR Co₂Z:), and 4.8 nH (Zn-Co-Ni + high Hk and fFMR Co₂Z:) at 2 GHz. The corresponding L-densities are 18.0, 22.4, and 19.2 nH/mm², which are greater than 16.8 nH/mm² of the air-core inductor. With respect to the Q factor, the air-core and ferrite inductors exhibit Q factors of 6.7 (air-core), 4.8 (Zn-Co-Ni), 2.8 (Zn-Co-Ni + low Hk Co₂Z), and 4.0 (Zn-Co-Ni + high Hk Co₂Z) at 2 GHz. The tan δμ of the ferrites caused a reduction in the Q factor. Nevertheless, the high Hk and fFMR Co₂Z ferrite inductor demonstrates a higher Q factor than that of the low Hk and fFMR Co₂Z inductor. It is, therefore, suggested that high-resistivity, -anisotropy, -magnetization ferrite can produce large L-density and Q-factor GHz inductors.

A low-profile three-current model is proposed to guide the design of an on-board antennas with a broad beam. Based on this model, an on-board three-element antenna is designed. When the side length of the ground is infinite, the 3-dB beamwidths in the xz plane and yz plane are all 180°, and the radiation pattern in the xy plane has a gain fluctuation less than 3 dB. When the side length of the ground is 2λ, the measured 3-dB beamwidths in the xz plane and yz plane are 141° and 148°, respectively. A quasi-hemispherical radiation pattern can be obtained based on the proposed three-current model.

The electromagnetic passive localization without the need of carrying any device, named device-free passive localization (DFPL) technique, is an emerging technology for determining an uncooperative target's position. The DFPL technique detects the shadowed links in a monitored area and realizes localization with the received signal strength (RSS) measurements of these links. However, most current RSS-based DFPL schemes belong to the model-based DFPL method, since the localization accuracy depends on the shadowing model. Moreover, model-based DFPL methods require high memory and computing resources for accurate tracking performance, and thus may not be suitable for resource-constrained applications. To overcome these problems, in this paper we propose a lightweight DFPL method which makes use of recent link lines detected by wireless sensor networks to estimate the target's location. This method can be independent of the shadowing model and can also reduce the algorithm's storage and computational resource requirements. The effectiveness and robustness of the proposed scheme are demonstrated by experimental results where the proposed algorithm yields substantial improvement for localization performance and complexity.

A compact wideband antenna consisting of a L-shaped radiating element which has a modified inverted-F structure and a C-shaped parasitic radiating element on the ground is proposed. Three resonant frequencies and a very wide operating band are obtained. A prototype of the proposed antenna has been constructed and experimentally studied. The measured results show that the operating bandwidth with 10 dB return loss is about 2.9 GHz (2.11-5.01 GHz), 81.46%, respectively, covering LTE2500 (2.5-2.69 GHz), 2.4 GHz WLAN and 2.5/3.5 GHz WiMAX bands. Furthermore, the antenna has a simple planar structure and small volume of only 30 × 30 × 1.6 mm³. Good radiation characteristics and acceptable peak gains are obtained over the operating bands.

The frequency-modulated continuous wave (FMCW) synthetic aperture radar (SAR) has the properties of compact size, lightweight, low cost and low power dissipation, which provides great potential in the application of small platforms such as unmanned aerial vehicle (UAV). The imaging characteristics of rotary target for FMCW SAR are analysed based on the construction of echo signal model. Further, a passive suppressing jamming method for FMCW SAR based on micromotion modulation is proposed. This method makes use of rotary corner reflector to form jamming strips in range and azimuth, and then the target screened is protected effectively. The choice of parameters of rotary corner reflectors is discussed in detail. Finally, some simulations are given to validate the theoretical derivation and the effectiveness of method.

The aim of this study is to present a dual-band antenna for Wireless Medical Telemetry Service (WMTS) applications. The antenna covers all three frequency bands 608-614 MHz, 1395-1400 MHz, and 1427-1432 MHz, and is intended for continuous health monitoring of patient's vital parameters. The designed antenna consists of a meandered dipole antenna and a superstrate layer to preserve the biocompatibility of the structure. It has a compact size with dimensions 17.6 mm x 12 mm x 2.54 mm. The measured -10 dB bandwidths are found to be 16.3% for the lower frequency band and 10.6% in the upper frequency band. The antenna is in vitro tested in a tissue mimicking solution.

The study of earth terrain in Antarctica is important as this region has a direct impact on global environment and weather condition. There have been many research works in developing remote sensing technologies, as it can be used as an earth observation technique to monitor the polar region (Giles et al., 2009; Park et al., 2012). In previous studies, remote sensing forward model has been developed to study and understand scattering mechanisms and sensitivity of physical parameters of snow and sea ice. This paper is an extended work from previous studies (Syahali et al., 2011; Syahali, 2012; Syahali and Ewe, 2012, 2013), where an improved theoretical model to study polar region was developed. Multiple-surface scattering, based on an existing integral equation model (IEM) that calculates surface scattering and additional second-order surface-volume scattering, were added in the model from prior research works (Ewe et al., 1998) for improvement in the backscattering calculation. We present herein the application of this model on a snow layer above ground which is modeled as a volume of ice particles that are closely packed and bounded by irregular boundaries above a homogenous half space. The effect of including multiple surface scattering and additional surface-volume scattering up to second order in the backscattering coefficient calculation of snow layer is studied for co-polarized and cross-polarized returns. Comparisons with satellite data are also done for validation. Results show improvement in the total backscattering coefficient for cross-polarized return in the studied range, suggesting that multiple-surface scattering and surface-volume scattering up to second order are important scattering mechanisms in the snow layer and should not be ignored in polar research.

This paper presents a new hybridization between MoM-GEC and a MultiResolution analysis (MR) based on the use of wavelets functions as trial functions. The proposed approach is developed to speed up convergence, alleviate calculation and then provide a considerable gain in requirements (processing time and memory storage) because it generates a sparse linear system. The approach consists in calculating the total current and input impedance on an invariant metallic pattern through two steps. The first one consists in expressing the boundary conditions of the unknown electromagnetic current with a single electrical circuit using the Generalized Equivalent Circuit method (GEC) and then deduce an electromagnetic equation based on the impedance operator. The impedance operator used here is described using the local modal basis of the waveguide enclosing the studied structure. The second step consists in approximating the total current using orthonormal periodic wavelets as testing functions and the local modal basis of the waveguide as basis functions. The proposed approach allows fast calculation of such inner products through the use of the wavelets multiresolution (MR) analysis advantages, thus significantly reducing the required CPU-time for microstrip-type structure analysis [13, 14]. A sparse matrix is generated from the application of a threshold. A sparsely filled matrix is easier to store and invert [15, 16]. Based on this approach, we study the planar structures. The obtained results show good accuracy with the method of moments. Moreover, we prove considerable improvements in CPU time and memory storage achieved by the MR-GEC approach when studying these structures.