A novel dual-band annular ring slot antenna is investigated. The antenna consists of a center-fed circular microstrip patch antenna with a coupled annular ring. And it is shorted concentrically with a set of conductive vias. By adjusting the parameters of the antenna, the dual resonant frequencies for two modes (TM₀₁ and TM₀₂ modes) are achieved. The antenna is fabricated and tested. Results show that the proposed antenna with height of 0.0217λ₀ can provide gains of 3.01 dBi at 2.6 GHz (the receiving frequency) and 5.74 dBi at 2.95 GHz (the transmitting frequency). Good agreement between the measurement and simulation for the return loss and radiation patterns is achieved. The proposed antenna has dual-band characteristics, simple structure, low profile, and omni-directional azimuth radiation pattern. It is suitable for aircraft both receiving and transmitting signals and frequency division duplex (FDD) applications.

Magnetic induction tomography (MIT) is a tomographic technique utilising inductive coils and eddy currents to map the passive electromagnetic properties of an object. Eddy current methods are widely used for non-destructive testing (NDT) in inspection of metallic structures. Eddy current based NDT uses a single coil or a pair of coils to scan the samples. As an emerging NDT technique, MIT scans the sample with a coil array through an eddy current based tomographic approach. In this paper, a planar array MIT system (PMIT) is proposed for 3D near subsurface imaging. This is of great importance as there are large numbers of potential applications for MIT that allow limited access to the materials under testing. The system development, practical implication, capability and limitations of PMIT are discussed. The fundamental principles are demonstrated through simulations. Experimental data are used to evaluate the capability and detectability this system has as a potential 3D subsurface imaging tool.

In high squint spotlight mode SAR, the coupling of the range and azimuth is very serious, which brings challenges to the imaging. In this paper, an extended frequency scaling algorithm is proposed, in which the range migration correction is divided into two steps. Firstly the range walk correction is implemented in 2D time domain. In the second step, the residual range migration is corrected by the frequency scaling and bulk shift operations. Though the second range compression does not consider the range space variance, the range compression is precise. In the azimuth compression, because of the range walk correction, the azimuth modulation frequency rate becomes dependent on the azimuth position. In order to equalize the azimuth modulation frequency rate, the azimuth nonlinear chirp scaling method is involved to remove the dependence. The simulation experiments verify the validity of the proposed algorithm. The comparison of the imaging quality among traditional frequency scaling algorithm, nonlinear frequency scaling algorithm and the proposed method indicates the proposed method is more suitable for the high squint spotlight SAR.

A single-side-access ring resonator topology is presented. It employs a single quarter-wavelength coupled-line that couples to a one-wavelength ring to exhibit a single-mode resonance with transmission zeros. A global synthesis is presented, in order to control the transmission zeros in its response. As the transmission zeros of the ring resonator maintains their positions when multiple identical rings are used, the global synthesis can further be used for the design of higher order filters with multiple rings. Furthermore, since only one coupled-line is used in the resonator topology, only one section of line is present in the ring, other than the coupled-line. Hence, there will be no second section of the ring that needs to be adjusted to obtain the symmetrical response during its realization, as compared to other types of ring topologies. To show the advantage of the synthesis, it is applied in the design of higher order ring-based bandpass filters, which also involve extra quarter-wavelength coupled-lines to create additional poles. Five bandpass ring filters up to 5th-order were realized using microstrip technology, and measured to validate the proposed concept. Measurement results showing good agreement with those from the simulation are also presented throughout the paper.

An improved UWB non-coplanar power divider is presented. Based on the theory of microstrip-to-slotline transition, the principle of this power divider is discussed. To improve the performances of the power divider, a tapered slot and a fan-shaped slot take the place of a circular slot in the circuit design. The simulated and measured results show a progressive return loss of input port.

A through wafer vertical micro-coaxial transition flushed in a silicon substrate has been designed, fabricated, and tested. The transition has been designed using radio frequency (RF) coaxial theory and consists of a 100μm inner diameter and a 300 μm outer diameter, which corresponded to a 1:3 inner/outer diameter ratio. The transition's through silicon structure has been achieved using standard photolithography techniques and Bosch's process for deep reactive ion etching (DRIE). The coaxial vias of the transition have been successfully metalized with a diluted silver paste using a novel filling method. To measure the behavior of the transition at high frequencies, coplanar waveguide (CPW) lines matched at 50 ohms have been integrated on the front and backside of the device. Measurement results show that the transition demonstrate good results with a reflection coefficient better than -10 dB at high frequencies from 15 GHz-to-60 GHz. Results also indicate that the transition has good signal transmission with less than -1.8 dB insertion loss up to 65 GHz. By eliminating the need for rigorous bonding techniques, the transition is a low-cost and durable design that can produce high input/output ratios ideal for commercial products.

This paper discusses the characterization of landmine by using the electromagnetic induction technique (EMI). The proposed approach is based on the identification of the physical and geometrical properties of a landmine, from the sensor response. But in such an identification, the inverse problem is unavoidable. At first, we begin by simulating the landmine signature by solving a direct problem using the finite element method which constitutes the direct model. After that, we determine the landmine characteristics by using an inverse model based on a cost function optimization. This model is based on an iterative process which coupling nite element analysis and Particles Swarm Optimization (PSO). In this step, we apply two PSO techniques: the Standard PSO (SPSO) and the Improved PSO (IPSO), and discuss the problem of local minima of the cost function. The proposed iterative model is applied to determine the conductivity, geometry, and depth of metallic landmine from its signature measured by EMI. The numerical solution gives good results for the identification of landmine.

In this work, we propose a merged coil structure for wireless chip-to-chip communication technology. Using the proposed coil structure, the chip size can be reduced, and the transmitted power can be improved by approximately 5 dB compared to typical coil structure. To verify the feasibility of the coil, an electromagnetic simulation and a schematic simulation are performed. The coil was implemented using 50-nm digital CMOS technology. From the experimental results, the feasibility was proved.

An ultra-wideband (UWB) antenna with a novel multi-layer frequency selective surface (FSS) reflector is presented. A significant enhancement in the gain has been achieved in a low profile design while maintaining the excellent impedance bandwidth of the UWB antenna. The average peak gain of the antenna has been increased from 4 dBi to 9.3 dBi as a consequence of the use of the FSS reflector. More importantly the gain variation within the frequency range from 3 GHz to 15 GHz is only ±0.5 dB. This is a significant improvement from ±2 dB gain variation of the UWB slot antenna without the reflector. This optimized FSS reflector provides the exibility of mounting a planar antenna close to conducting bodies, including screens and cases.

A method to control the transmission zero of TE_01δ mode dielectric-resonator (DR) filters for wireless base stations is proposed. Instead of using folder structures, dedicated coupling probes, or extra cavities, as required by conventional techniques, transmission zeros are realized. The feeding probes, extended along ring dielectric resonators, are used to excite the TE_01δ mode and introduce transmission zeros. By rotating the angle of feeding position, transmission zeros can be shifted to the lower or the upper stopband. Thus, TE_01δ mode dielectric resonator filters with quasi-elliptic responses are realized with only iris coupling components. Based on this method, fourth-order inline TE_01δ mode DR filters with different responses are designed and fabricated. Measured results confirm the predicted performance.

A compact waveguide(CPW)-fed dual-frequency planar monopole antenna is proposed, which can excite two modes.The antenna is composed of a epsilon negative (ENG) meta-structured transmission line (MTL) unit cell and a monopole. The first resonance is zeroth-order mode,which is described using dispersion relation of ENG MTL based on Bloch and Floquet and designed on a CPW single layer where vias are not required. And the second is electromagnetically coupled monopolar mode. The zeroth-order resonant phenomenon is employed to reduce the antenna size. To design and analyze the proposed antenna, the circuit simulation of the ENG MTL unit resonator is executed by the equivalent circuit, and the results are compared with those of full wave simulation and experiment. The results show that the presented antenna reasonable radiation characteristics of bandwidth gain and size, verified by a commercial EM simulation software HFSS11, and is suitable for compact dual-frequency antenna. Then the antenna is fabricated and measured. The realized antenna has a compact size of 0.288λ₀ x 0.199λ₀ x 0.011λ₀(25.1mm x 17.4 mm x 1 mm) at 2.43 GHz. Simulated and experimentally measured results show that the proposed antenna can operate at 2.41(2.43) GHz and 4.11(4.14) GHz bands, respectively. Good agreement between the simulated and measured results is obtained.

This paper presents two simple analytical models of the switched reluctance motor. The first model is constructed on two flux linkage-current characteristics, the aligned position one calculated via finite element analysis (FEA), and the unaligned position characteristic calculated by using motor geometry data. The second model is based on three flux linkage-current characteristics, the aligned, unaligned and average one, obtained by employing the FEA. In both cases the direct and inverse models are defined. The models consider the core nonlinearity and the influence of the rotor position on the motor behavior. The estimated magnetizing and torque characteristics are compared with that calculated via two dimensions FEA for a switched reluctance motor (SRM) sample and with the test bench obtained ones. The merits and the drawbacks of the models are evinced.

An impedance-permeability (Z-μ_r) resonance phenomenon is firstly founded and numerically demonstrated when electromagnetic metamaterials with negative permeability are firstly introduced into inductance coil. Numerical results reveal that the impedance-permeability relationship exhibits an extraordinary self-resonant phenomenon at a certain negative value of relative permeability, which is related to the dimensions of the core but nearly independent to the coil size. Such a mechanism is proposed to increase the sensitivity of eddy current (EC) sensors up to about 270 times, offering a new method to greatly improve the sensitivity of EC sensors and the spatial resolution with micrometer scale.

Low loss circular birefringence is found in three-dimensional artificial triple helices. High values of chirality index are generated. Within the transmission bandwidth, there is a significant difference in the refractive index value of the right- and left- polarized waves. The outgoing waves from a wedge structure designed from these triple helices are proved to split with a wide angle. The wave polarizations agree with earlier simulation results.

This paper presents a design of perforated nanoantenna reflectarray. The use of metallic nanostructures made of Silver and/or Gold at appropriate wavelength cause fascinating unusual electromagnetic effects. Reflectarray consists of an array of unit cell made from Silver is investigated. The effect of the number of perforated holes in the unit cell configurations is investigated for proper reflection coefficient phase compensation. A linearly polarized pyramidal nano-horn is used to feed the perforated nanoantenna reflectarray. The radiation characteristics of 9 × 9 perforated nanoantenna reflectarray are illustrated. A high gain of 20.5 dB is obtained at the designed frequency of 735 THz. A comparison between solid Silver sheet with no perforation holes and the proposed perforated reflectarray is explained.

In this paper an in-depth parametric analysis of shielding effectiveness obtained when using ferromagnetic or conductive screens to mitigate the field generated by duct banks is presented. Due to the need of a case-by-case approach, all the simulations, performed by a finite element software (GetDp), are applied to a case study composed by 9 (3x3) ducts, with six of them including high voltage single-core cables and the three left empty for eventual future expansion. Two shielding geometries are tested: horizontal and U-reverse, changing in each one the main parameters: width, thickness, clearance to conductors, etc. Moreover, the conductors are grouped in two balanced in-phase three-phase circuits arranged in three configurations: vertical, horizontal and triangular. The mutual phase ordering of both circuits is the one that minimizes the field, so no further field reduction can be obtained by simple methods. The power losses and cost of different shielding solutions are also presented, including the effect of adding a third circuit if required.

In this paper, the applications of chiral layers and metamaterials as radar absorbing materials are investigated. A perfect electric conductor plate covered by a chiral metamaterial is considered and after the formulation of the problem, reflection of the structure under an oblique plane wave incidence of arbitrary polarization is investigated. Then several examples of the applications of chiral layers in nondispersive, dispersive, and chiral nihility conditions are provided to design of zero reflection coatings. Finally, application of chiral metamaterial structures as microwave absorbers is discussed. In some of the provided examples, the method of genetic algorithm is used to optimize chiral coatings for the minimization of co- and cross reflected power.

In this paper, we present an efficient Artificial Neural Network (ANN)-based model to estimate both azimuth and elevation arrival angles of a signal source. To achieve this goal, the ANN model is constructed using measurement data obtained by a rectangular antenna array in the space-frequency domain. Unlike classical super-resolution algorithms such as 2D MUSIC, the proposed model is capable to account for imperfections of measurement equipment as well as mutual couplings between array elements. The neural model has been verified for several angular positions and frequencies. It is shown that use of ANN model to estimate angular positions of a signal source yields more accurate results when compared to 2D MUSIC. Moreover, the neural model significantly outperforms 2D MUSIC in terms of speed of computation.

It is potentially useful to perform target identification using micro-Doppler features because they contain information on the geometrical structure of the target. In this paper, the m-D effect of the rotationally symmetric ballistic target (BT) is analyzed which reveals that the m-D is not a form of sinusoidal modulation due to the sliding-type scattering. Inspired by the extended Hough transform (EHT), a method to extract all the six parameters of the BT is proposed. The m-D effect and the performance of feature extraction algorithm are demonstrated by the measured data in a microwave anechoic chamber.

The theory and design of a new family of multifrequency monopole antennas by smartly loading a set of complementary metamaterial transmission line (CMTL) unit cells are investigated. The distributed CMTL elements, epsilon negative (ENG) or double negative (DNG) through incorporating additional capacitive gaps, contain a Koch-shaped extended complementary single split ring resonator pair (K-ECSSRRP) etched on the signal strip. The K-ECSSRRP features dual-shunt branches in the equivalent circuit model, rendering a distinguished resonator with dual zeroth-order resonant (ZOR) modes. By smartly controlling the element layout and loading different numbers of unit cells, ten antennas covering different communication standards (GSM1800, UMTS, Bluetooth, DMB and WIMAX) are designed and four of them are fabricated and measured. At most of operating frequencies, the antennas exhibit impedance matching better than -10 dB and normal monopolar radiation patterns. Numerical and experimental results both confirm that the single-cell or dual-cell ENG and DNG CMTL-loaded monopoles exhibit almost identical dual ZOR modes. Moreover, the loaded elements also contribute to the radiation, which is the major advantage of this prescription over previous lumped-element loadings. These antennas are compact and the multiple operating bands can be arbitrarily engineered, enabling an alternative and easy avenue toward monopoles with multifunction and high integration.