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Abstract The future of computational electromagnetics is changing drastically with the new generation of computer chips, which are multi-cored instead of single-cored. Previously, advancements in chip technology meant an increase in clock... more
Abstract The future of computational electromagnetics is changing drastically with the new generation of computer chips, which are multi-cored instead of single-cored. Previously, advancements in chip technology meant an increase in clock speed, which was typically a ...
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The far field of an antenna is generally considered to be the region where the outgoing wavefront is planar and the antenna radiation pattern has a polar variation and is independent of the distance from the antenna. Hence, to generate a... more
The far field of an antenna is generally considered to be the region where the outgoing wavefront is planar and the antenna radiation pattern has a polar variation and is independent of the distance from the antenna. Hence, to generate a locally plane wave in the far field the radial component of the electric field must be negligible compared to the transverse component. Also, the ratio of the electric and the magnetic far fields should equal the intrinsic impedance of the medium. These two requirements must hold in all angular directions from the antenna. The radial and the transverse components of the fields are space dependent so to determine the starting distance of the far field we need to examine the simultaneous satisfaction of these two properties for all θ and φ angular directions, where θ is the angle measured from z-axis and φ is the angle measured from the x-axis. The objective of this paper can be summarized in three points: First, this paper intends to illustrate that 2D2/λ formula, where D is the maximum dimension of the antenna and λ is the operating wavelength, is not universally valid, it is only valid for antennas where D ≫ λ. Second, this paper intends to compute a more specific constraint so instead of D ≫ λ we compute a threshold for D after which the 2D2/λ formula applies. Third, this paper intends to properly interpret D in the formula 2D2/λ when the antenna is operating over an imperfect ground plane. In this paper, we do not use 2D2/λ for antennas operating over an imperfect ground instead we use a formula which depends on the transmitting and receiving antenna's heights over the air-Earth interface.
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A hands-on approach to avoid scientific debates and confusions about surface waves and Zenneck waves are presented. The reflection coefficient for a TM incident wave on a flat boundary is studied as a function of the medium parameters in... more
A hands-on approach to avoid scientific debates and confusions about surface waves and Zenneck waves are presented. The reflection coefficient for a TM incident wave on a flat boundary is studied as a function of the medium parameters in the most general way. When the second medium is lossy, the zero of this function results in a Zenneck wave and an infinite value represents a surface wave. Even though both Zenneck and surface waves are evanescent in nature and thus non-radiating, the field distribution for a Zenneck wave does not change with frequency whereas that of a surface wave gets concentrated near the surface with an increase in frequency. Finally a Zenneck wave can be excited by an electromagnetic wave but a surface wave requires electrons or quasiparticles in the form of an evanescent wave to be excited. Important questions are raised about some misused terminologies involving these two waves.
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The Electrically Small Antennas (ESAs) perform well compared to larger antennas under matched conditions. In this paper, we study the difficulties in achieving a good design of an ESA matched to 50 O system. These difficulties are... more
The Electrically Small Antennas (ESAs) perform well compared to larger antennas under matched conditions. In this paper, we study the difficulties in achieving a good design of an ESA matched to 50 O system. These difficulties are summarized in three topics: First, the Quality (Q) factor of an ESA, in general, is high and cannot be less than the Chu limit. The Q factor of an antenna is inversely proportional to the bandwidth of the antenna so this will impose a limit on the bandwidth of the antenna. Second, losses are always there in the impedance matching network, these losses associated with the matching network can dominate the small radiation resistance of an ESA which will degrade the efficiency of the ESA. Third, we are limited by the Fano-Bode gain-bandwidth limit when using the lossless passive matching network techniques. To overcome these issues, several solutions are presented briefly, either we try to alter the shape of the ESA so as to make the Q factor of the antenna close to the optimum lower limit or to use the concept of non-Foster matching networks to overcome the Fano-Bode limit. Finally, we design a four-arm meander line folded monopole which is considered an ESA at 1 GHz; it is shown that this design is matched to 50 Ω with low quality factor.
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Measurements of-Band n-Type InSb Junction Circulators.................. ZM Ng, LE Davis, and R. Sloan 482 An RF Electronically Controlled Impedance Tuning Network Design and Its Application to an Antenna Input Impedance Automatic Matching System................. J. de Mingo, A. Valdovinos, A. Cre...more
In this paper, a newly developed MoM code using higher-order basis functions and a parallel out-of-core solver, TIDES, is run on a high performance parallel computing cluster. An aircraft carrier model and an airborne antenna array with... more
In this paper, a newly developed MoM code using higher-order basis functions and a parallel out-of-core solver, TIDES, is run on a high performance parallel computing cluster. An aircraft carrier model and an airborne antenna array with radome are analyzed in this paper to demonstrate the TIDES code's capability. Numerical results indicate that TIDES provides an excellent solution for this
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Received signal level measurements are frequently used to check the performance and the Quality of Service (QOS) inside the coverage area in cellular networks. These expensive time consuming measurements are carried out using an actual... more
Received signal level measurements are frequently used to check the performance and the Quality of Service (QOS) inside the coverage area in cellular networks. These expensive time consuming measurements are carried out using an actual drive tests to assess the coverage area of a base station for a given cell and thus evaluate the QOS. In this paper, the novelty of the proposed electromagnetic analysis technique lies in its ability to match the macro model based simulation and measurement results without any statistical or empirical curve fitting or an adhoc choice of a reference distance. Furthermore, a new concept called proper route has been introduced to enhance the quality of measured data. The input parameters for the electromagnetic macro model can be generated using only the physical parameters of the environment like the height of the transmitting and receiving antennas over the ground, their tilts toward the ground, and the electrical parameters of the ground. A method of moments-based integral equation solver code called AWAS has been used to simulate the effects of the macro parameters of the environment. Measurements were carried out for cellular networks in western India and Sri Lanka.
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ABSTRACT This presentation offers a historical overview on the evolution of field theory for wireless communications.
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ABSTRACT This paper presents a thin and compact high gain planar antenna integrated with a CMRC compact filter. The high gain antenna is a 4 element broadside microstrip array fed by parasitic coupling. The antenna is developed on a thin... more
ABSTRACT This paper presents a thin and compact high gain planar antenna integrated with a CMRC compact filter. The high gain antenna is a 4 element broadside microstrip array fed by parasitic coupling. The antenna is developed on a thin substrate of 0.762 mm thick. The broadside gain is 11.37 dBi at 5.5 GHz. The CMRC filter has filtered out the higher order modes of the micostrip antenna till 16 GHz. The sizes of the antenna array with and without the CMRC filter are exactly the same. Therefore, the design presented is a promising technique in designing a thin and compact high gain planar antenna with low-noise received.
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A method to obtain an accurate band-pass filter model from numerically computed or measured data is presented. A modified new version of the Cauchy technique that uses simultaneously both transmission (S21(f)) and reflection (S11(f))... more
A method to obtain an accurate band-pass filter model from numerically computed or measured data is presented. A modified new version of the Cauchy technique that uses simultaneously both transmission (S21(f)) and reflection (S11(f)) parameters is applied in order to find a rational polynomial characterization of the filter. From this rational model the coupling structure can be extracted, revealing the
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ABSTRACT A discrete finite time domain pulse is designed under the constraint of the Federal Communications Commission (FCC) ultrawideband (UWB) spectral mask. This pulse also enjoys the advantage of having a linear phase over the... more
ABSTRACT A discrete finite time domain pulse is designed under the constraint of the Federal Communications Commission (FCC) ultrawideband (UWB) spectral mask. This pulse also enjoys the advantage of having a linear phase over the frequency band of interest and is orthogonal to its shifted version of one or more baud time. The finite time pulse is designed by an optimization method and concentrates its energy in the allowed bands specified by the FCC. Finally, an example is presented to illustrate how these types of wideband pulses can be transmitted and received with little distortion.
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ABSTRACT This work presents an analytical method for extraction of cascaded fully canonical second order blocks, formed by two resonators with a direct input-output coupling that generates two transmission zeros. Starting from the... more
ABSTRACT This work presents an analytical method for extraction of cascaded fully canonical second order blocks, formed by two resonators with a direct input-output coupling that generates two transmission zeros. Starting from the transfer matrix of the complete network and the specification of the transmission zeros, the method finds a decomposition of the transfer polynomials into two new sets corresponding to the second order subnetwork and the remaining one. To do so, the general solution of the extracted block transfer matrix is computed at each transmission zero. Then, both solutions are used to solve the complete polynomials. In order to illustrate the use of the algorithm, an analytical synthesis of a seventh order filter with four transmission zeros is included. The network topology corresponds to two cascaded quadruplets sharing one resonator.
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ABSTRACT This letter proposes a design of single-layer microstrip ultrawideband (UWB) 90° differential phase shifter. The operating bandwidth covers the UWB frequency range from 3.1-10.6 GHz. The design is optimized using a transmission... more
ABSTRACT This letter proposes a design of single-layer microstrip ultrawideband (UWB) 90° differential phase shifter. The operating bandwidth covers the UWB frequency range from 3.1-10.6 GHz. The design is optimized using a transmission line model and an electromagnetic model, and have been fabricated using a plotter dealing with generation of printed circuits. The measured S11 is better than -10 dB and S21 is better than -0.96 dB within the UWB frequency range. The simulated and measured phase deviation of the differential phase shift are 90°±5.23° and 90°±9.02°, respectively. The advantages of the proposed design are the simple fabrication, low insertion loss, and broad bandwidth.
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ABSTRACT The purpose of this paper is to demonstrate that the recently published paper [1] dealing with little known facts and some new results on transmission lines is due to an incomplete interpretation of the nonphysical artifacts... more
ABSTRACT The purpose of this paper is to demonstrate that the recently published paper [1] dealing with little known facts and some new results on transmission lines is due to an incomplete interpretation of the nonphysical artifacts resulting from a particular mathematical model for the S parameters. These artifacts are not real and do not exist when a different form of the S parameters is used.The first objective of this paper is thus to introduce the two different types of S parameters generally used to characterize microwave circuits with lossy characteristic impedance. The first type is called the pseudo wave, an extension of the conventional traveling-wave concepts, and is useful when it is necessary to discuss the properties of a microwave network junction, irrespective of the impedances connected to the terminals. However, one has to be extremely careful in providing a physical interpretation of the mathematical expressions, as in this case the reflection coefficient can be greater than one, even for a passive load impedance with a conjugately matched transmission line. The power balance also cannot be simply obtained from the powers associated with the incident and reflected waves. Hence, this cannot be applied for broadband characterization of antennas. The second type of S parameter is called the power-wave scattering parameter. This is useful when one is interested in the power relationship between microwave circuits connected through a junction. In this case, the magnitude of the reflection coefficient cannot exceed unity, and the power delivered to the load is directly given by the difference between the powers associated with the incident and the reflected waves. Since this methodology deals with the reciprocal relationships between powers from various devices, this may be quite suitable for dealing with a pair of transmitting and receiving antennas where power reciprocity holds. This methodology is also applicable in network theory, where the scattering matr- x of a two-port (or a multi-port) can be defined using complex reference impedances at each of the ports without any transmission line being present, so that the concept of characteristic impedances becomes irrelevant. Such a situation is typical in small-signal microwave transistor amplifiers, where the analysis necessitates the use of complex reference impedances in order to study simultaneous matching and stability. However, for both definitions for the S parameters, when the characteristic impedance or the reference impedance is complex, the scattering matrix does not need to be symmetric, even if the network in question is reciprocal.The second objective is to illustrate that when the characteristic impedance of the line or the reference impedances in question is real and positive, then both of the pseudo-wave and the power-wave scattering parameters provide the same results. Finally, a general methodology is presented with examples to illustrate how the S parameters can be computed for an arbitrary network without any a priori knowledge of its characteristic impedance.
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Theoretical and Experimental Study of Interference in Multibeam Active Phased Array Transmit Antenna for Satellite Communications...................................................... KJ Maalouf and E. Lier 587 Reduction of Truncation Error in Near-Field Measurements of Antennas of Base-Station M...more
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ABSTRACT
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Estimation of the Direction Of Arrival (DOA) of broadband signals is presented based on a single snapshot of data using an interpolation methodology. The goal is to simultaneously estimate the DOA of all the signals along with their... more
Estimation of the Direction Of Arrival (DOA) of broadband signals is presented based on a single snapshot of data using an interpolation methodology. The goal is to simultaneously estimate the DOA of all the signals along with their respective frequencies of operation using a single snap shot of the voltages measured at the antennas. Numerical results are presented to illustrate
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ABSTRACT The objective of this presentation is to illustrate the art of writing a parallel code that exploits an out-of-core solver.
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In this paper, a hybrid MoM and PO method is proposed to speed up the computation time and reduce the memory requirement of a regular integral equation based MoM solver. It has been shown that in the frequency domain a MoM based integral... more
In this paper, a hybrid MoM and PO method is proposed to speed up the computation time and reduce the memory requirement of a regular integral equation based MoM solver. It has been shown that in the frequency domain a MoM based integral equation solver when merged with a PO solution methodology can lead to an efficient and accurate solution methodology for the analysis of electrically large problems. In this paper, the same concept is extended to such a combination in the time domain for transient scattering analysis from large structures. Sample numerical results are presented to illustrate these improvements.
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This paper presents an accurate dynamic methodology for computing the frequency responses of multilayered ground planes filled with inhomogeneous dielectric materials. Since an integral equation based method based on the free space... more
This paper presents an accurate dynamic methodology for computing the frequency responses of multilayered ground planes filled with inhomogeneous dielectric materials. Since an integral equation based method based on the free space Green's function has been utilized for computing the current distribution on the structures, the edge effects from the ground planes can be accurately accounted for, resulting in a more accurate model in the gigahertz regions. It provides great flexibility in computation of the impedance at any location between the various planes. The results have been compared with the S-parameters measured by other researchers and show good correlation with the available measurements
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An improved Green's function analysis for rectangular stacked (and single) patch antennas enclosed in a cavity is described. A very efficient representation of Green's dyad for the internal problem, leading to... more
An improved Green's function analysis for rectangular stacked (and single) patch antennas enclosed in a cavity is described. A very efficient representation of Green's dyad for the internal problem, leading to greatly improved convergence of the numerical results, has been implemented. Comparison with measured results confirmed the suitability of the formulation discussed for input impedance computation
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The finite element or finite difference techniques are well known for the solution of Maxwell's equation in differential form. But terminating the mesh accurately at a finite distance from the body in case of an open problem is a... more
The finite element or finite difference techniques are well known for the solution of Maxwell's equation in differential form. But terminating the mesh accurately at a finite distance from the body in case of an open problem is a major challenge. The method of [4]-[5] is applied for only electrostatic problem. This hybrid method is applied for TM scattering problem and results are documented in this paper. This new approach, as in the electrostatic case, allows for the terminating surface to encapsulate the body very tightly. As before, finite element technique is used for open region problems whereas integral equation solution approach using Green's function is applied to enforce the radiation condition. At each iteration cycle, the induced currents on the conducting cylinder are evaluated and their scattered field at the terminating surface is calculated. Using this method for TM case, the computational efficiency of finite element method can be increased. It can be generalized for the case of inhomogeneous and nonlinear media, for static and dynamic fields. In this paper numerical results are presented for the solution of Helmholtz's equation to illustrate the accuracy of the technique.
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... Magdalena Salazar-Palmd& Luis-Emilio Garc(aCastillo*, Ruben Ramirez-Garc(a* Mateo Burgos-Garcia, Jose-Ignacio Alonso-Montes*, Jos6-Luis ... and J,, are displayed (J i and J,.414are irrelevant in thiscase); several... more
... Magdalena Salazar-Palmd& Luis-Emilio Garc(aCastillo*, Ruben Ramirez-Garc(a* Mateo Burgos-Garcia, Jose-Ignacio Alonso-Montes*, Jos6-Luis ... and J,, are displayed (J i and J,.414are irrelevant in thiscase); several buttons allow to save the corresponding file, to visualize and ...
Research Interests: Engineering, Computer Science, Microwave, Design method, Dielectric Resonator Antenna, and 14 moreFrequency, Transfer Function, Prototypes, Band Pass Filter, Microstrip, Band Pass, Passives and Actives Microwaves Circuits Design, Insertion Loss, Transfer Functions, Amplitude, Software Package, Scattering parameters, Prototype filter, and Band pass filters
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Research Interests: Mathematics, Computer Science, Electromagnetism, Computational Complexity, Algorithm, and 15 moreAntenna arrays, Numerical Simulation, DFT, Accuracy, Matrix Multiplication, Antenna Array, Multiplication, DOA Estimation, Electromagnetic wave propagation, Mutual Coupling, Electrical And Electronic Engineering, Azimuth, Discrete Fourier Transform, Direction of arrival, and Near Field
Research Interests: Mathematics, Orthogonal polynomials, Low Frequency, Electromagnetic Field, Composite Structure, and 12 moreHermite Polynomials, Three Dimensional, Laguerre polynomial, Time Domain, Laguerre function, Electrical And Electronic Engineering, Orthogonal Polynomial, Laguerre Polynomials, Frequency Domain, Electromagnetic Analysis, Hybrid Method, and Polynomial
A fast algorithm is presented for solving electric, magnetic, and combined field time-domain integral equations pertinent to the analysis of surface scattering phenomena. The proposed two-level plane wave time-domain (PWTD) algorithm... more
A fast algorithm is presented for solving electric, magnetic, and combined field time-domain integral equations pertinent to the analysis of surface scattering phenomena. The proposed two-level plane wave time-domain (PWTD) algorithm permits a numerically rigorous reconstruction of transient near-fields from their far-field expansion and augments classical marching-on in-time (MOT) based solvers. The computational cost of analyzing surface scattering phenomena using
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Research Interests: Mathematics, Computer Science, Antennas, Wireless Systems, Electromagnetics, and 12 moreMagnetic field, System Design, Communication Technology, Wireless Technology, Wireless, Electric Field, Wireless Communication, Electrical And Electronic Engineering, Channel Capacity, Electric and Magnetic Fields, Near Field, and Line of sight
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This paper introduces an anti-jamming technology for satellite communication that can cancel terrestrial jammers. In this paper, we first consider the Conjugate Gradient Method (CGM) as the first adaptive algorithm. Using this method, the... more
This paper introduces an anti-jamming technology for satellite communication that can cancel terrestrial jammers. In this paper, we first consider the Conjugate Gradient Method (CGM) as the first adaptive algorithm. Using this method, the attainment of the depth of the nulls and the rate of convergence are shown to be excellent. We also introduce a second novel adaptive algorithm, the hardware complexity of which for real-time implementation remains within the capacity of an off-the-shelf serial processor. A simulator based on the proposed adaptive algorithms is then illustrated to verify the performance of an adaptive system designed for implementation on a geostationary satellite. Finally, we demonstrate a hardware implementation of the adaptive system for canceling terrestrial jammers. Detailed hardware descriptions of an implemented adaptive system - such as the antenna array module, the beamforming module, and the controller module - are illustrated, along with the results of the performance obtained in laboratory tests.
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... Available online 18 October 2004. Abstract. A hybrid finite element method (FEM) and high frequency technique (HFT) for the efficient analysis of the radiation and scattering of electromagnetic waves on complex environments is... more
... Available online 18 October 2004. Abstract. A hybrid finite element method (FEM) and high frequency technique (HFT) for the efficient analysis of the radiation and scattering of electromagnetic waves on complex environments is presented. ...
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Abstract This work proposes the use of split ring resonators (SRRs) as basic blocks for planar filters with dual-band band-pass frequency response. This application requires some geometrical modifications on the original SRRs used for... more
Abstract This work proposes the use of split ring resonators (SRRs) as basic blocks for planar filters with dual-band band-pass frequency response. This application requires some geometrical modifications on the original SRRs used for metamaterial synthesis. The ...
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We present a new technique for estimating the parameters of damped sinusoids utilizing both early and late time transient scattering data contaminated by noise. Transient scattering responses are composed of damped sinusoids at late times... more
We present a new technique for estimating the parameters of damped sinusoids utilizing both early and late time transient scattering data contaminated by noise. Transient scattering responses are composed of damped sinusoids at late times and impulse-like components at early times. In this study the entire noisy time domain response is used to extract the signal parameters of interest. The half Fourier transform (HFT) is used to analyze the data for parameter identification. Impulse or Gaussian-like pulses can be easily separated from the damped exponentials in the HFT domain, as they have similar functional representations. Results from several examples show that the new technique is applicable for noisy signals that are composed of damped exponentials and pulse-like components.
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The objective of this paper is to illustrate how these problems can be best handled on scalable affordable personal computer clusters. The authors propose to achieve this goal through the use of out-of-core matrix solvers. Since, the... more
The objective of this paper is to illustrate how these problems can be best handled on scalable affordable personal computer clusters. The authors propose to achieve this goal through the use of out-of-core matrix solvers. Since, the authors do not require RAM but hard disk to deal with the storage, now the problem can be handled at an affordable personal level. Examples are presented on how this goal can be accomplished.