In this paper, a modified square slot antenna with modified radiating patch, for UWB applications is proposed. The proposed antenna consists of a square radiating patch with a double fed structure and a ground plane with a pair of L-shaped slots which provides a wide usable fractional bandwidth of more than 140% (3--18 GHz). By optimizing the L-shaped slots dimensions and rectangular slot width, the total bandwidth of the antenna is greatly improved. The designed antenna has a small size of 35×35 mm².

We use both FEM (finite element method) and FDTD (finite difference time domain method) to simulate the field distribution in Maxwell's fish eye lens with one or more passive drains around the image point. We use the same Maxwell's fish eye lens structure as the one used in recent microwave experiment [arXiv:1007.2530]: Maxwell's fish eye lens bounded by PEC (perfect electric conductor) is inserted between two parallel PEC plates (as a waveguide structure). Our simulation results indicate that if one uses an active coaxial cable as the object and set an array of passive drains around the image region, what one obtains is not an image of the object but only multiple spots resembling the array of passive drains. The resolution of Maxwell's fish eye is finite even with such passive drains at the image locations. We also found that the subwavelength spot around the passive drain is due to the local field enhancement of the metal tip of the drain rather than the fish eye medium or the ability of the drain in extracting waves.

In this paper the microwave images of two-dimensional section of multiple objects are formed by using the wideband range profiles of the target. Scattered electric field is obtained by the designed two-dimensional imaging system and Fourier transformed into the highly-resolved range profiles while the target rotates. A filtered back-projection (FBP) algorithm is implemented to form the image from the space domain range profiles. Images of multiple cylindrical rods from both numerically simulated and measured data indicate that the approached imaging scheme can achieve high dynamic range and can be potentially implemented for biomedical imaging detections.

The research in the paper puts forward a novel method for synthesizing conformal arrays and optimizing low cross-polarizations including the effects of element mutual coupling and mounted platform. Starting from the far-field superposition principle, an efficient approach with active element pattern technique is proposed to calculate the far-field patterns. Coordinate transform is used to create polarization quantities, and a general process for the element polarized pattern transformation is proposed. The two numerical examples are proposed, and the desired sidelobe levels and low cross-polarizations are optimized. Numerical results denote the proposed method is valid.

The reflection of linearly polarized light from an ultrathin biaxially anisotropic dielectric film on an isotropic transparent material is investigated in the long-wavelength limit. The approximate expressions for the reflection characteristics of s- and p-polarized electromagnetic plane waves are obtained. The analytical approach developed in this paper not only provides insight into the nature of reflection problem for biaxially anisotropic ultrathin films but also furnishes the methods for resolving the inverse problem for such anisotropic layers. It is shown that a key capability of the developed analytical method is to decouple the usual correlations in the index and the thickness of ultrathin films.

A modified UWB power divider formed by installing one delta stub on each branch is proposed. Delta stub is used as a substitution of radial stub that can present wideband characteristic. The proposed structure makes branch line shorter and stub's size smaller than those of similar works based on UWB power divider using radial stub. It also achieves a compact size of 18 mm by 13 mm. The simulation and measurement results of the developed divider are presented and shown good agreement in the UWB range.

In the present paper a dual frequency resonance antenna is achieved by introducing half U-shaped slot in semicircular disk. It is analysed by using circuit theory concept. The resonance frequency is found to be 1.50 GHz and 2.32 GHz, and the bandwidth of the proposed antenna for lower and upper resonance frequency is found to be 5.96% and 11.08% respectively. It is found that the resonance frequency depends inversely on the slot length and feed point, while it increases with increasing the slot width and coaxial probe feed radius. The frequency ratio is found to be 1.54. The theoretical results are compared with IE3D simulation as well as reported experimental results, and they are in good agreement.

The objective of this paper is to establish the properties of the electromagnetic wave propagation in a diversity of situations in material media with magnetic monopoles and even in the situations of entities simultaneously containing electric and magnetic charges. This analysis requires the knowledge and solutions of the ``Maxwell" equations in material media compatible with the existence of magnetic monopoles and the extended concepts of linear responses (conductivity, split-charge susceptibility, kinetic susceptibility, permittivity and magnetic permeability) in the case of presence of electric and magnetic charges. This analysis can facilitate insights and suggestions for electrical and optical experiments according a better knowledge of the materials whose behaviour can be analyzed under the consideration of the existence of entities with equivalent properties of the magnetic monopoles.

This work proposes a substrate integrated waveguide (SIW) power divider employing the Wilkinson configuration for improving the isolation performance of conventional T-junction SIW power dividers. Measurement results at 15 GHz show that the isolation (S₂₃, S₃₂) between output ports is about 17 dB and the output return losses (S₂₂, S₃₃) are about 14.5 dB, respectively. The Wilkinson-type performance has been greatly improved from those (7.0 dB~8.0 dB) of conventional T-junction SIW power dividers. The measured input return loss (23 dB) and average insertion loss (3.9 dB) are also improved from those of conventional ones. The proposed Wilkinson SIW divider will play an important role in high performance SIW circuits involving power divisions.

In this work, magnetic metallic cobalt nanoparticles with an average particle size of 28 nm were processed as a dry powder with surface coating material and other organic additives to form a screen-printable ink to be cured at 110 °C. EFTEM and TGA-DSCMS-analyses were used to measure the thickness of the polymer, its coverage on cobalt nanoparticles and the inorganic solid content of the ink. The resolution of the printed patterns and the print quality were evaluated by surface profiler, FESEM and optical microscopy. The relative permeability of the thick film patterns with good printability was measured with a shorted microstrip structure over the frequency range of 0.2 to 4 GHz and complex permeability values were calculated from measured scattering parameter data. The ink attained real part of complex permeability values of up to 5.13 at 200 MHz with 70 wt.% of magnetic filler. The developed ink can be utilized in various printed electronics applications such as antenna substrates and magnetic sensors.

In this paper, we consider the imaging of thin dielectric inclusions completed embedded in the homogeneous domain. To image such inclusion from boundary measurements, topological derivation concept is adopted. For that purpose, an asymptotic expansion of the boundary perturbations that are due to the presence of a small inclusion is considered. Applying this formula, we can design only one iteration procedure for imaging of thin inclusions by means of solving adjoint problem. Various numerical experiments without and with some noise show how the proposed techniques behave

In this paper the definition of characteristic impedance for lossless microstrip and coplanar lines has been considered. It has been shown that due to a significant value of the displacement current related to longitudinal component of the electric field, impedance definition becomes ambiguous. Such ambiguity can cause considerable errors in design procedure. This effect is especially noticeable in the coplanar lines, in opposite to microstrip ones. To confirm the validity of the applied algorithm (spectral domain approach) the propagation coefficients and characteristic impedances have been compared to values obtained from commercial software.

This paper proposes a radio frequency identification (RFID) based collision-free robot docking in cluttered environment. Physical distance estimation sensors are fused to the developed degree of arrival (DOA) guided robot docking system, and collision-avoidance function is implemented based on the vector field histogram technique. Additionally, new simple but efficient DOA filtering algorithm is developed based on the gain control according to the improved robot control algorithm, which enables the robot to move continuously. The experimental results show that the robot can move to target transponder even though the estimated DOA is blocked by obstacles. The success rate does not reach satisfactory level due to the limitation of the employed sensors and collision-avoidance algorithm, but it is proved that the collision-free docking becomes available without any priori map and reference stations.

A new adjustable Electromagnetic Band-Gap (EBG) structure whose frequency response is controllable by adjusting spacer height is proposed. The finite difference time domain method is adopted for the simulations. Results show that the desired frequency response can be selected by adjusting the spacer height. The effects of the air-gap on the polarization dependent and conventional EBG structures have been investigated both theoretically and numerically. The agreement between the theoretical calculations and numerical results is reasonably good.

In this paper, a novel hybrid dielectric resonator (DR) antenna for Ultrawideband (UWB) short-range wireless communications is proposed. The proposed antenna consists of a microstrip fed monopole loaded with a half cylindrical dielectric resonator antenna of Rogers RO3010 mounted on RT5880 substrate with a finite ground plane. The microstrip line fed monopole antenna is on the other side of the substrate. Compared to the conventional circular cylindrical DR mounted on a finite ground plane (reference antenna), the proposed antenna has a reduction in the antenna size by about 30% with a bandwidth increase by about 22% than the reference antenna. The proposed antenna has a good impedance bandwidth. In addition, the proposed antenna has a quite higher and more stable gain than that of reference antenna. Moreover, the antenna has a good omni-directional radiation patterns in the H-plane. The proposed antenna is considered a good candidate for UWB short-range wireless communication systems.

A bandwidth improvement method in reflectarray antennas by using closely space elements, i.e. unit-cell sizes smaller than λ/2, has been investigated both numerically and experimentally in this paper. A new definition of phase error has been introduced to analyze the broadband mechanism of closely spaced phasing elements. Through full wave EM simulations, it is revealed that closely spaced elements achieve a smaller phase error over the band. Based on these theoretical studies two Ka-band reflectarrays were fabricated and their performance was measured across the frequency range of 30 to 34 GHz. It is demonstrated that the reflectarray designed with closely spaced elements achieves a notable improvement in gain bandwidth performance.

We propose a circularly polarized microstrip patch antenna using artificial magneto-dielectric (AMD) substrate. The proposed antenna has a square patch with dual feeding point using Wilkinson power divider in order to achieve circularly polarized radiation pattern. The AMD substrate is constructed by single sprit ring resonators, which are arrayed in both x and y directions. The designed antenna has the characteristics of the axial ratio less than 1.7 dB, the peak gain of 0.55 dBic, and the right handed circular polarized radiation pattern at Korea UHF RFID service band. The sizes of the antenna and radiating patch are 100 mm×100 mm×5.2 mm and 65 mm×65 mm (0.199λ₀×0.199 λ₀), respectively.

A thick metal microstrip diplexer is presented. The circuit is based on compact folded half wavelength resonators and uses a source/load-multi-resonator coupling method providing improved performance and greater design flexibility. Source/load coupling with multiple resonators introduces additional transmission zeros, and this coupling is enhanced by using high-aspect-ratio metal structures. Tall, narrow metal arms connected to the ports and extended to the non-adjacent resonators provide effective multi-resonator bypass coupling. The high-aspect-ratio diplexer fabricated using polymer-based deep X-ray lithography and 0.22 mm thick metal electroplating demonstrates the advantages of thick metal structures for coupled resonator applications.

To describe propagation of polarized electromagnetic wave within a disperse random medium a new Monte Carlo based technique with an adopted vector formalism has been developed. The technique has been applied for simulation of coherent backscattering of circularly polarized optical radiation from a random scattering medium. It has been found that the sign of helicity of circular polarized light does not change for a medium of point-like scatterers and can change significantly for the scatterers with the higher anisotropy. We conclude that the helicity flip of the circular polarized light can be observed in the tissue-like media. We find that this phenomenon manifests itself in case of limited number of scattering events and, apparently, can be attributed to the pulse character of incident radiation rather than to the specific form of scattering particles.

In this study, transmission characteristics of a novel THz wire waveguide --- conical metal wire with dielectric coating at 0.1-1 THz are studied. The investigation results show that the coated conical wire with virtually low attenuation and high energy concentration is a promising candidate as THz transmission medium. The calculation results agree well with that of simulation such as high frequency structure simulation (HFSS), which is based on the finite element method. In this paper, a novel transition from a coaxial line to the coated conical metal wire is designed. Although coaxial probe excitation has been used in microstrip lines and rectangular waveguides in microwave, millimeter-wave frequency domains, the present study shows that it is also an effective method to excite conical wire at THz frequency. As shown in the investigation results, the return loss of coax-conical wire transition is better than 20 dB from 0.1-0.5 THz, and the insertion loss is as low as 1 dB (the total length is 15 mm). It is a promising THz transition structure.