A microstrip antenna design is introduced in which aperture coupled rectangular microstrip patch is coupled electromagnetically with a parasitic gridded rectangular patch placed above. The gridded patch consists of nine identical rectangular parts separated by a distance which is much smaller than a free space wavelength for a central frequency. The antenna is designed to operate in the 60 GHz band and is fabricated on a conventional PTFE (polytetrafluoroethylene) thin substrate. Different published arrangements for parasitic patches are studied. For the same substrate and central frequency the proposed antenna has improved return loss bandwidth and gain bandwidth for approximately the same maximum gain. Measurement results are in good agreement with simulation. Measured 10 dB return loss bandwidth is from 54 GHz up to 67 GHz. It fully covers the unlicensed band around 60 GHz. The measured antenna realized gain at 60 GHz is close to 8 dB, while the simulated antenna radiation efficiency is 85%. A simple beam shifting method is possible for this antenna structure by connecting adjacent outside parts in the gridded patch. The designed antenna is suitable for a high speed wireless communication system in particular for a user terminal in a fifth generation (5G) cellular network.
This paper presents a novel approach for solving the frequency responses of a powerline network, which is a two-parallel-conductor system with multiple junctions and branches. By correcting the reflection coefficient and transmission coefficient of each junction, a complex network can be decomposed into several, single-junction, units. Based on the Baum-Liu-Tesche (BLT) equation, we preliminarily propose the calculation method of frequency responses for single-junction network. In accordance with the direction of power transfer, we calculate the frequency responses of loads connected to each junction sequentially, from the perspective of the network structure. This approach greatly simplifies the computational complexity of the network frequency responses. To verify the proposed algorithm, networks with various numbers of junctions and branches are investigated, and the results are compared with a commercial electromagnetic simulator based on the topology. The analytical results agree well with the simulated ones.
Nowadays new safety related systems design include electromagnetic analysis (EMA) during their development. Each of these systems is composed by smaller apparatuses that contain electronic components able to emit electromagnetic (EM) waves. On the other hand, the usage of smaller integrated circuit increase their susceptibility to EM interference. Companies often underestimate the importance of emissions lower than standard limits. A method based on near-field (NF) to far-field (FF) transformation is introduced in order to evaluate radiated emission leakage. This study is an important novelty to analyze electromagnetic issues in the case of safety related systems. Moreover, authors presented how this method is positioned as to current standards. Effectively NF-FF is proposed for site survey analysis on assembled systems where EM leakages should be mitigated to avoid EM attacks. Tools and measurements presented here can be used to sketch the virtual EM (VEM) interface of device-under-test (DUT) in terms of emissions amplitude, frequency and direction. An opponent could use this information to jam these systems utilizing an attack model based on a circular antenna here presented. The results indicate that it is feasible to use this methodology to analyze EM radiated emissions starting from NF information. Compared with current immunity test levels, the EM attack planned on VEM interface characteristics can be deemed efficiently against safety related systems.
In the paper presented here the optimization of Halbach arrays as storage media for mechanical potential energy is investigated with numerical simulations using FEMM and analytical calculations using the Maxwell stress tensor. Two opposing Halbach arrays form a ``magnetic spring'' and mechanical potential energy is stored when this structure is compressed. It is here seen that the wavelength of the magnetization in the material and the dimensions greatly in fluence the stored energy density. A clear region of maximum is identified which leads to important conclusions on how the material should be employed. The suggested approach for storing energy have advantages and approximately 250 kJ/m^{3} can be reached. The main drawback is the large prize of rare earth metals such as Neodymium.
We characterize the alpha power and chirped types of refractive index profile planar slab waveguide in terms of TE/TM mode study, waveguide dispersion study, mode profile properties, power confinement factor and universal b-V graph. Our own developed finite element method has been efficiently applied to analyze the symmetric planar slab waveguide having a complicated refractive index profile. There is a requirement for a high accuracy of numerical technique to analyze the arbitrary refractive index waveguide, as at some frequency the TE and TM modes are smeared on each other, and it is difficult to distinguish them while analyzing. This paper successfully demonstrates the different TE/TM modes supported by the waveguide with respect to alpha-power and linearly chirped types of refractive index profile. The main contribution of our work is to identify the TE/TM mode numerically for a complex refractive index planar slab waveguide and to characterize them in terms of their performance parameters. Then we apply the mode propagation concept to estimate the propagation phenomena in alpha-power and chirped types of refractive index profile waveguide. All the results presented in this paper are simulated in MATLAB only. Our study reveals that waveguide dispersion and number of allowed guided modes are small while for the case of triangular index profile followed by chirped profile and maximum for step index profile case. Hence triangular and chirped types of refractive index profile waveguide seem to be more efficient for long haul optical communication systems.
It is generally believed that antenna correlations of up to 0.5 in magnitude have negligible effects on the performance of multi-antenna systems, and that antenna correlation only affects the system performance via its magnitude. In this paper, we show that antenna correlations of 0.5 in magnitude that has negligible effect in capacity (i.e., theoretically maximum data rate) can cause noticeable degradation on the throughput (i.e., actual achievable data rate); and that, when the number of antennas is larger than two, the phase of the correlation also has an impact on the performance of multi-antenna system. We demonstrated these via simulations and measurements in a reverberation chamber.
In this paper, a SPICE model representative for the mode conversion occurring in differential lines affected by imbalance either of the line cross-section and the terminal networks is developed. The model is based on the assumption of weak imbalance and allows approximate prediction of modal quantities, through separate modeling of the contributions due to line and termination imbalance by controlled sources with (possibly) frequency dependent gain. The proposed SPICE model is used to perform worst-case prediction of undesired modal voltages induced at line terminals by mode conversion.
Multitarget tracking (MTT) in surveillance system is extremely challenging, due to uncertain data association, maneuverable target motion, dense clutter disturbance, and real-time processing requirements. A good many methods have been proposed to cope with these challenges. However, no up-to-date survey is available in the literature that can help to select suitable tracking algorithm for practical problem. This paper provides a comprehensive review of the state-of-the-art motion-based MTT techniques, classifies existing methods into two groups, i.e., the detect-before-track (DBT) scheme and the track-before-detect (TBD) scheme. The DBT scheme is employed to achieve robust and tractable tracking performance when the signal-noise-ratio (SNR) is strong. The TBD scheme is used in the scenarios of low SNR, and it aims to cumulate target energy by multiple sensor frames. Furthermore, depending on the data association mechanism, the DBT methods can be classified into two categories, data association based approaches and finite set statistics (FISST) based approaches. And the TBD methods can be classified into non-Bayesian approaches and Bayesian approaches depending on the basis theory used for tracking. For each category, this paper provides the detailed descriptions of the representative algorithms, and examines their pros and cons. Finally, new trends for future research directions are offered.
This paper studies the effect of three important parameters in planar time-domain (TD) near-field (NF) to far-field (FF) transformation. These parameters are the NF spatial sampling, NF measurement distance and scan surface truncation. The effect of these parameters over the TD FF accuracy are difficult to predict for Ultra Wide Band antennas. In this paper we aim to choose the optimum NF measurement parameters guaranteeing accurate calculation of the time-domain far-field. This allows the optimization of the computation time and memory requirements. Computations using analytic array of elementary dipoles radiation pattern are used to study the impact of each parameter in time-domain near-field antenna measurement. The comparison of the far-field results are presented in time and frequency domains. In particular, it is shown that the choice of the measurement distance and the size of the scan surface decide predominantly on the frequency band of accurate FF calculation. The used formalism in this paper for the NF to FF transformation is based on the Green's function.
By virtue of their ability to resonate at a wavelength much larger than the maximum dimension, Split-Ring Resonator (SRR) cells can be densely stacked to create energy harvesting arrays having per-unit-area power efficiency higher than a single SRR cell. While the concept of using metamaterial particles for electromagnetic energy harvesting had been demonstrated in our earlier work, the overall efficiency of an SRR array in comparison to classical antenna arrays is fundamental to the viability of this technology. In this work, we focus on a comparative study based on numerical full-wave simulations where an array of SRRs is compared to an array of microstrip antennas. We show that an SRR array can provide significant enhancement in power efficiency and bandwidth in comparison to the classical microstrip patch antenna. Experimental validation is provided showing SRR arrays can provide significant energy-absorption enhancement.
In this paper, the modal theory of antennas is re-visited, believing that it brings invaluable information towards facilitating the design of multi-feed multi-band antennas. First, some subtle changes are proposed to enhance the applicability of thetheory. Next, using some efficient computational techniques, the proposed formulations are shown to predict, to a very high accuracy, the input impedance of any antenna under study. This greatly simplifies the antenna problem and focuses design efforts on finding the appropriate complex resonance frequency to cover a required band. Finding the appropriate feed location is then a matter of extracting the corresponding impedance map for this antenna through simple field manipulations.
A problem of the spherical antenna consisting of a thin radial monopole located on a perfectly conducting sphere is solved. The antenna is excited at the base by a voltage δ-generator. An approximate analytical solution of the integral equation for the current on a thin impedance vibrator was found by the method of successive iterations. The solution is physically correct for arbitrary dimensions of the spherical antenna and for any value of surface impedance distributed along the monopole. The validity of the problem formulation is provided by using the Green's function for the Hertz vector potential in unbounded space outside the perfectly conducting sphere and by writing the initial integral equation for the current on the monopole. Influence of the monopole dimensions and surface impedance upon the radiation characteristics and the input impedance of the spherical antenna is studied by numerical evaluations using zero order approximation. The input impedance of the monopole was determined by the method of induced electromotive forces (EMF) using the current distribution function thus obtained.
Microwave absorbers find a plethora of applications in the modern-day military and civil industries. This paper compares the performance of different variations of the Particle Swarm Optimization (PSO) algorithm to obtain optimal designs for multilayer microwave absorber over different frequency ranges, angles of incidence and polarizations. The goal of this optimization is to minimize maximum overall reflection coefficient of the absorber by choosing suitable layers of materials from a predefined database and simultaneously make the overall thickness the least practically possible. Numerical optimal results for each variation of the PSO are presented and the best results are compared with those existing in literature.
For microwave imaging systems that utilize antennas with spatially separated feeds and apertures, arrival time correction based on the antenna aperture location is one of the fundamental steps in radar data processing. The estimates of the antenna aperture time and the corresponding average velocity in the material in contact with the antenna are expected to have a significant impact on the quality of the reconstructed image. In this paper, we propose antenna aperture and average velocity estimation by least-squares regression analysis of the first-breaks. The results indicate that the proposed method is able to process either the reflection data or the transmission data measured by antennas with different structures. Compared to those readily identifiable characteristics in the signal, the first-break is less influenced by waveform distortion and is able to provide more consistent reference. Differences in the images of test objects are also noted.
Novel eagle shape microstrip wearable antennas (element and array) are presented. The single- and two-element antenna arrays are designed and fabricated on a Roger RT/Duroid 5880 substrate with dielectric constant of 2.2, thickness of 1.5748 mm, and tan δ = 0.001. The measured results show that a reduction in mutual coupling of 36 dB is achieved at the first band (1.68-2.65) GHz and 22.1 dB over the second band (6.5-8.86) GHz due to introducing electromagnetic bandgap (EBG) structures. EBG structure has an eagle-like shape with more gaps. By increasing the number of EBG cells and varying the gap distance between cells to certain limit, the mutual coupling reduction is improved. Also, a size reduction of 80% is achieved. The microstrip array was simulated by CST simulator version 2014 and fabricated by proto laser machine with precision 25 μm. The specific absorption rate (SAR) investigation is carried out on CST2014 Simulator. Maximum SAR value is 1.953 W/Kg which indicates that the eagle-shaped microstrip wearable antennas are safe for human. The antennas can be used in the official or RFID applications.
Studying of mutual coupling parameters between the antenna elements in an array environment has been considered as the subject of feature research. That is why, in this paper, we present a new Floquet modal analysis procedure for analyzing almost periodic structures. Accurate evaluation of the mutual coupling could be achieved by this analysis. It is shown how Floquet analysis can be exploited to study a finite array with arbitrary amplitude and linear phase distribution in both x-y directions including mutual coupling effects. Two different calculation methods of coupling coefficients between the array elements are presented, in spectral and spatial domains, to solve the suggested problem. For modeling the given structures, the moment method combined with Generalized Equivalent Circuit (MoM-GEC) is proposed. High gain in the running time and memory used is given using Floquet analysis. To validate this work, several examples are shown.
This paper deals with the magnet pole shape design for the minimization of cogging torque in permanent magnet synchronous machines (PMSM). New shapes of permanent magnet are proposed. The magnet shape is modeled analytically by a set of stacked and well dimensioned layers relatively to the height and opening angle. The final shape of magnet is configured by using three models in view of obtaining lower magnitude of cogging torque. A 2-D exact analytical solution of magnetic ﬁeld distribution taking into account the shape of magnet, the irregular mechanical thickness of air-gap and semi-closed stator slots is established. The influence of motor's parameters such as the number of stator slots per pole and per phase and PM's magnetization on cogging torque is discussed. Analytical results are validated by the static finite-element method (FEM).
In modeling electromagnetic phenomena randomness of the propagation medium and of the dielectric object should be taken up in the model. The usually applied Monte-Carlo based methods reveal true characteristics of the random electromagnetic field at the expense of large computation time and computer memory. Use of expansion based methods and their resulting algorithm is an efficient alternative. In this paper the focus is on characteristics of electromagnetic fields that satisfy integral equations where the integral kernel has a random component, typically, electromagnetic fields that describe scattering due to dielectric objects with an inhomogeneous random contrast field. The assumption is that the contrast is affinely related to a random variable. The integral equation is of second kind Fredholm type so that its solutions are determined by the resolvent, a random operator field. The key idea is to expand that operator field with respect to orthogonal polynomials defined by the probability measure on the underlying sample space and to derive the properties of the solution from that expansion. Two types of illustration are presented: an inhomogeneous dielectric slab and a 2D dielectric grating with 1D periodicity.
Variety of designs for artificial magnetic materials have been proposed in the literature. in most designs such as split-ring resonators, the inductive and capacitive responses of metallic inclusions are dependent since the area and perimeter of the resonators' geometry cannot be tuned independently. In this work, three generic resonators for the design of artificial magnetic materials are proposed. The resonators are called rose curve resonator, corrugated rectangular resonator, and sine oval resonator. The proposed resonators' patterns are characterized so that their areas and perimeters vary independently. Thus, the geometries are capable of satisfying any realizable combination of area and perimeter designed for an artificial magnetic material with desired properties. Numerical studies are considered showing the effectiveness of the new geometries to fulfil design specifications.
This study concerns the 2D inverse problem of the retrieval, using external field data, of either one of the two physical parameters, constituted by the real and imaginary parts of the permittivity, of a z-independent cylindrical dielectric specimen subjected to an external, z-independent, quasistatic electric field. Six other parameters enter into the inverse problem. They are termed nuisance parameters because: 1) they are not retrieved during the inversion and 2) uncertainty as to their actual values can adversely affect the accuracy of the retrieval of the permittivity. This inverse problem is shown to have an exact, mathematically-explicit, solution, both for continuous and discrete input data, whose properties, with respect to the various nuisance parameter uncertainties, are analyzed, first in a mathematical, and subsequently in a numerical manner for noiseless data. It is found that: a) optimal inversion requires data registered at only a small number of sensors, b) the inverse solution, satisfying pre-existing physical constraints, exists and is unique. Moreover, the inverse solution is shown to be unstable with respect to three nuisance parameter uncertainties, the consequence of which is large retrieval inaccuracy for small nuisance parameter uncertainties, acting either individually or in combination.