A compact stack antenna consisting of square loop resonators, aperture couples, feed line and the perturbation for dual-band and circular polarization (CP) applications is proposed in this paper. This perturbation applies both dual-mode and orthogonal mode effects existing in the square loop resonator to present wide-band and CP characteristics simultaneously. The stack antenna presents the desired bands of 2.46 GHz with bandwidth (BW) = 160 MHz (6.58%) and 5.28 GHz with BW = 450 MHz (8.52%). The circular polarizations for dual-band are demonstrated with axial ratio (AR) spectrum and orthogonal modes. The proposed antenna is successfully simulated and measured with frequency responses, radiation patterns and current distributions.

The paper deals with the analysis of the magnetic field distribution near the transition tower of an overhead-underground transmission line of 110 kV. The current density induced in the human body due to this field is also estimated. A hybrid numerical technique combining both the boundary element method and the charge simulation method is employed for this purpose. This technique is implemented in the author's own software package dedicated to the analysis of electromagnetic exposure in the vicinity of power objects. A simplified numerical model of the human body of dimensions recommended by the IEC/EN standards is employed in computations. Obtained numerical results are related to the appropriate regulations regarding the human exposure to the electromagnetic fields.

The synthetic aperture radar (SAR) signatures of moving target are the basis of ground moving target indication and imaging (GMTI&Im) in the framework of SAR systems. However, previous studies are mainly based on the 2-D separable SAR processing, and little work has been done to investigate the signatures of moving target after the application of a particular fine resolution SAR image formation algorithm. In this paper, we derive the image spectrum of moving target after two representative fine resolution SAR image formation algorithms, i.e., the range migration algorithm (RMA) and polar format algorithm (PFA), respectively. Based on the spectrum derived, detailed analysis on the SAR signatures of moving target, including the geometric displacement, residual range migration, and defocusing effect in both the range and azimuth dimensions are performed. The presented work might be helpful when considering a SAR system with the capability of ground moving target indication and imaging (GMTI&Im).

We introduce a novel variant of the Lanczos method for computing a few eigenvalues of sparse and/or dense non-Hermitian systems arising from the discretization of Maxwell- or Helmholtz-type operators in Electromagnetics. We develop a Krylov subspace projection technique built upon short-term vector recurrences that does not require full reorthogonalization and can approximate simultaneously both left and rigth eigenvectors. We report on experiments for solving eigenproblems arising in the analysis of dielectric waveguides and scattering applications from PEC structures. The theoretical and numerical results reported in this study will contribute to highlight the potential and enrich the database of this technology for solving generalized eigenvalue problems in Computational Electromagnetics.

The performance of a short dipole antenna closely located above a finite High-Impedance Surface (HIS) is addressed. The antenna behavior is thoroughly analyzed in the frequency range up to the HIS resonance within the region where the propagation of the TE surface waves is not allowed. In the first part of the paper the analysis of a dipole antenna above a grounded dielectric slab is considered, and then it is extended to the case of a substrate with a frequency selective surface printed on it. For all configurations, the radiation pattern of the structure and Front-to-Back Ratio (FBR) are reported and compared. It is shown that the presence of a suitable frequency selective surface, regardless of the shape of the periodic elements, guarantees the antenna matching but does not influence the behavior of the radiation patterns and the front-to-back ratio in the frequency range where only TM modes are allowed to propagate. The front-to-back ratio has been found to be maximum when the size of the generic HIS is around 0.8λ_g (with λ_g the TM guided surface wave wavelength). All the speculations are supported by simulated and measured results.

In this paper, we propose a hybrid optimization approach that combines the Efficient Global Optimization (EGO) algorithm with Taguchi's method. This hybrid optimized algorithm is suited for problems with expensive cost functions. As a Bayesian analysis optimization algorithm, EGO algorithm begins with fitting the Kriging model with n sample points, and finds the (n+1)th point where the expected improvement is maximized to update the model. We employ Taguchi's method in EGO to obtain the (n+1)th point in this paper. A numerical simulation demonstrates that our algorithm has advantage over the original EGO. Finally, we apply this hybrid optimized algorithm to optimize an ultra-wide band (UWB) transverse electromagnetic (TEM) horn antenna and a linear antenna array. Compared to Taguchi's method and the Integer Coded Differential Evolution Strategy, our algorithm converges to the global optimal value more efficiently.

The objective of this work is to analyze electronic transport phenomena, due to ionized impurity scattering in δ-MIGFET (Delta-Multiple Independent Gate Field Effect Transistor). In this work, we report theoretical results for electronic transport in a delta-MIGFET using the device electronic structure and analytical expression of mobility and conductivity. The results show that the analytical mobility and conductivity are a good way to analyze transport in this device. We find the relative mobility as a linear and increasing function in different modes; also, we find transconductance as an almost flat function in all the evaluated interval. Finally, we analyze the differential capacitance and resistivity, and we report regions where this device is operating in digital and analogue mode. These regions are delimited in terms of intrinsic and extrinsic parameters of this device in symmetrical mode.

An original iterative method based on the conjugate gradient algorithm is developed in this paper to study electromagnetic scattering. The Generalized Equivalent Circuit (GEC) method is used to model the problem and then deduce an electromagnetic equation based on the impedance operator. For validation purposes, the developed method has been applied to various iris structures. Results computed using the new implementation of the conjugate gradient are similar to theoretical values. The field and current distribution are identical to the ones obtained with the moment method. Moreover, the memory resources required for storage are significantly reduced.

We present a novel approach for adjoint transient sensitivity analysis with respect to discontinuities with space-dependent materials exhibiting known distribution. Our approach integrates the Time Domain Transmission-Line-Modeling (TD-TLM) with the Adjoint Variable Method (AVM). Using only one extra TD-TLM simulation, the sensitivities of the observed response with respect to all the parameters of the Gaussian distribution are obtained. The accuracy of our sensitivity analysis approach is illustrated through a number of different 2D and 3D examples. Using the previous sensitivities, gradient-based optimization technique is applied to exploit in the location and profile of various inhomogeneous material Gaussian distribution for inverse problems. This method can be repeated for any continuous or discontinuous distributions that exist in electromagnetic imaging for space dependent materials like cancer detection.

This paper presents a novel third-order cross-coupled rectangular cavity filter by using standard low-temperature co-fired ceramic (LTCC) technology, in which the multilayer substrate integrated waveguide (SIW) is implemented. Particularly, the desired filter has a single finite frequency attenuation pole at j4.0 with asymmetrical frequency selectivity. An experimental band pass filter (BPF) has been fabricated and measured. The insertion loss of the filter is better than 4.2 dB, and the 1 dB bandwidth is about 1 GHz at the center frequency 35.8 GHz. Good agreement is obtained between the simulated and measured S-parameters of the proposed filter. This filter can be used in millimeter wave secondary surveillance radars.

I present an algorithm to simulate low-frequency electromagnetic propagation in an anisotropic earth, described by a general (non-diagonal) conductivity tensor. I solve the electric formulation by explicitly imposing an approximate form of the condition ∇·J = 0, where J is the current density vector, which includes the source and the induced current. The numerical algorithm consists of a fully spectral explicit scheme for solving linear, periodic parabolic equations. It is based on a Chebyshev expansion of the evolution operator and the Fourier and Chebyshev pseudospectral methods to compute the spatial derivatives. The latter is used to implement the air/ocean boundary conditions. The results of the simulations are verified by comparison to analytical solutions obtained from the Green function. Examples of the electromagnetic field generated by a source located at the bottom of the ocean illustrate the practical uses of the algorithm.

A novel UWB bandpass filter (BPF) based on the composite right/left-handed (CRLH) material and 0° feeding structure is proposed. With multiple unit-cells cascaded, the new section comprises the series interdigital capacitors and the shunt short-circuited stub inductors in the symmetric configuration. The circuit is designed to be unbalanced, a tunable gap between left handed and right handed modes in the β-ω diagram can control out of band performance. With careful design, a bandpass filter with wide rejection band can be achieved. Furthermore, by using the 0° feeding associated structure, two extra transmission zeros are created just outside the intended passband. Finally, a three cells bandpass filter has been designed and fabricated with 1.1 dB insertion loss at the center frequency of 4.2 GHz. Two transmission zeros are located at 2.95 GHz and 6.18 GHz with attenuations of -44.1 dB and -37.3 dB, respectively. Also, a wide rejection band from 5.4 to 9 GHz is obtained.

In this paper, we present a wideband on-chip K-band RF front-end including a transmitter and a receiver for vehicular FMCW radar applications using a 0.18 μm CMOS process. To achieve wideband performance, an RC feedback circuit is applied to the input stage of amplifiers, as well as wideband passive circuits such as Marchand type baluns and Wilkinson type power dividers to the mixer LO port and transmitter output, respectively. The designed chip shows a 3-dB bandwidth of 6 GHz and 4.8 GHz for the receiver and transmitter, respectively. The receiver represents a gain of 18 dB and an input-referred 1 dB compression point of -9 dBm at an RF frequency of 24.15 GHz and an IF frequency of 100 kHz. The transmitter shows a power gain of 8.9 dB and an output power of 6.8 dBm at a frequency of 24.15 GHz. The total chip has a size of 1500 μm x 1270 μm while consuming 71 mA with a supply voltage of 1.8 V. Further, the designed RF front-end chip, also, has been verified by radar performance tests such as the Doppler shift and range detection. The test result for range information shows good agreement with theoretical expectation.

Two recent methods that have been reported in the literature to improve the performance of pyramidal horns are metal baffle loading and the use of epsilon-near-zero metamaterial. In this paper, a comparative study of the two methods is undertaken for the case of Ku- and X-band horns. In addition to the simulation study, a C-band metal baffle loaded horn was fabricated and rigorously characterized. It emerges from the study that E-plane metal baffle loading improves the radiation characteristics of the horn much better than the loading by metamaterial. Furthermore, the baffle loading nearly retains the construction simplicity, weight and cost of the normal pyramidal horn.

Performance of the sensing patch technique for measuring the power accepted at the antenna feed port of active patch antennas has been evaluated at harmonic frequencies. A prototype antenna, including two sensors at appropriate locations, was fabricated and tested at the fundamental and two harmonic frequencies to estimate the power accepted by the antenna, including determination of the sensor calibration factor.

A generalized version of the weighted-averages method is presented for the acceleration of convergence of sequences and series over a wide range of test problems, including linearly and logarithmically convergent series as well as monotone and alternating series. This method was originally developed in a partitionextrapolation procedure for accelerating the convergence of semiinfinite range integrals with Bessel function kernels (Sommerfeld-type integrals), which arise in computational electromagnetics problems involving scattering/radiation in planar stratified media. In this paper, the generalized weighted-averages method is obtained by incorporating the optimal remainder estimates already available in the literature. Numerical results certify its comparable and in many cases superior performance against not only the traditional weighted-averages method but also against the most proven extrapolation methods often used to speed up the computation of slowly convergent series.

In this paper, we make an assumption that the inertia vibrations of the electron groups in the rock fragment of the crack tips generate EMR pulses during the fracture of rocks. Based on this assumption we develop an oscillating dipoles model to analyze and simulate the EMR phenomena induced by the rock fractures. Then we use this model to simulate the EMR pulses recorded in the Rabinovitch's compression experiments on granite and chalk. Our simulations indicate a comparable accordance with Rabinovitch's experimental results. From our simulation results, we also find that the crack width associates with the maximum EMR voltage peak value.

Power strength or Received Signal Strength Indicator (RSSI), a primary technique used in Real Time Location Systems (RTLS), is analyzed in this paper for RFID tracking applications. Critical issues are studied and hardware novelties are introduced in order to improve its performance. The main novelty is the accomplishment of an RFID RTLS through a mesh of individual active radiofrequency (RF) barriers composed by active emitter and receiver nodes/tags that cover only small individual areas. The result is a Sensor Area Network (SAN) that offers some advantages over classical tracking systems, which are based on Wireless Sensor Networks (WSN), especially in the multipath impairment mitigation, such as a controlled power emission, and the chance to warrant privacy regarding the exchange of RFID information. Experimental measurements were done to estimate the influence of the transmitted signal type and the receiver end architecture in the detection of the RF barrier presence. The parameterization of the coverage area of a SAN cell in terms of power is derived for both free-space and log-distance propagation models. The Kalman filtering technique is introduced as a valid tool to severely mitigate the multipath propagation effects that can affect the accurate operation of the proposed SAN for indoor operation conditions. Outcomes show a promising performance for this wireless network design, which has not received enough attention in literature.

A novel low-pass filter (LPF) is designed and fabricated based on stepped-impedance resonator (SIR). Semi-circles are used to reduce the size of the filter. The open-circuited stubs are used in the filter, and its simplified equivalent circuit is also proposed. The measured 3 dB cutoff frequency is 5.2 GHz with no more than 0.3 dB ripple level in the pass-band. From 5.5 to 14 GHz, the investigated LPF has a rejection level batter than 20 dB. Measured results show good agreement with simulated ones.

In this paper, a traveling wave Koch dipole antenna is proposed. The antenna is an amalgamation of traveling wave antennas that require large elctrical lengths and fractal curves that are known for excellent form factor characteristics. The antenna is analyzed using a Mom code. The antenna exhibits an impedance bandwidth that is more than 10:1 for VSWR < 3:1. A comparision of simulated and measured results are presented. The traveling wave fractal antenna has many potential applications in communications and electronics warfare.