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Publications (861)
Conventional direction of arrival (DOA) estimation methods based on subspace decomposition are computationally complex and difficult to implement in practical applications. Although a fix step size least mean square (FSS-LMS) algorithm for DOA estimation has overcome the complexity problem, however the manual selection of suitable step size is diff...
In scenarios of rapidly moving interference and look direction error, the robustness and the output signal to interference and noise ratio (SINR) of conventional wideband adaptive beamforming methods will be degraded severely. In order to solve these problems, a robust wideband adaptive beamforming with null broadening and constant beamwidth is pro...
The objective of this special issue is to publish papers related to the basic physics of Electromagnetism in thecontext of radio wave propagation, see editorial of Part I
[1]
.
The time-domain electric integral equation methods (TD-EFIE) suffer from the numerical stability problem. Numerous schemes have been proposed over the years for the purpose of taking care of this instability. Among them, the marching-on-in-degree (MOD) method is one of the newly proposed algorithms for calculating the various transient responses. T...
Discrete interference influences the performance of existing space-time adaptive processing (STAP) methods in practical scenarios. In order to effectively suppress discrete interference in real clutter environment, a discrete interference suppression method based on robust sparse Bayesian learning (SBL) is proposed for airborne phased array radar....
The marching-on-in-degree (MOD) method has been proposed for solving time domain integral equations (TDIE), and it uses the associated Laguerre functions as temporal basis and testing functions. Although the MOD scheme is assumed to be stable and accurate, there exists little investigation on the accuracy of the integral operations involving the as...
This paper summarizes the lessons learnt in using a physics based macro model in studying electromagnetic wave propagation over an imperfectly conducting ground in cellular wireless communication. Firstly, it has ben observed that the path loss exponent is independent of the nature of the ground parameters inside the cell of interest. Secondly, the...
The objective of this paper is to illustrate that computational electromagnetics can be used very effectively to improve the accuracy and efficiency of antenna pattern measurements. This is accomplished by moving a single probe over the measurement plane to generate enhanced accuracy in planar near field to far field transformation than over the cl...
In his seminal article [1], Gabor observed that
Communication theory has up to now been developed mainly on mathematical lines, taking for granted the physical significance of the quantities which figure in its formalism. But communication is the transmission of physical effects from one system to another, hence communication theory should be consi...
This paper presents a physics based macro model that can predict with a high degree of accuracy the various experimental data available for the propagation path loss of radio waves in a cellular wireless environment. A theoretical macro model based on the classical Sommerfeld formulation can duplicate the various experimental data including that of...
This paper provides a survey of various experimental data available on the value of the propagation path loss of radio waves in a cellular wireless environment. It is shown starting with the Okumura et al.'s paper on propagation measurements and other available published experimental data that they all exhibit that the electric field varies as ρ
<s...
In this paper, an adaptive processing is carried out simultaneously at multiple frequencies using the same antenna array consisting of non-uniformly spaced dissimilar antenna elements. The antenna array may not be deployed in free space but may be located over an imperfect ground plane. First to correct for the various electromagnetic effects affec...
A non-standard Schwarz Domain Decomposition Method is proposed as finite element mesh truncation for the analysis of infinite arrays. The proposed methodology provides an (asymptotic) numerically exact radiation condition regardless the distance to the sources of the problem and without disturbing the original sparsity of the finite element matrice...
Compared with the uniform linear array (ULA), the co-prime array can obtain large array aperture with fewer array elements, which is good to improve the accuracy of direction-of-arrival (DOA) estimation. However, most of existing DOA estimation methods is not suitable for co-prime array because of high computational complexity and low adaptability....
For the suppression of rapidly moving interferences in wideband beamforming, an adaptive null broadening method is proposed. In the proposed method, the taper matrix is calculated by adding virtual interferences around original interferences. Then, based on the obtained taper matrix and the sample covariance matrix, the covariance matrix is reconst...
This chapter presents the necessary mathematical formulations, which dictate the space‐time behavior of antennas. It briefly reviews the derivation of the four equations and illustrates how to solve them analytically. The four equations consist of Faraday's law, generalized Ampère's law, generalized Gauss's law of electrostatics, and Gauss's law of...
Broadband antennas are very useful in many applications as they operate over a wide range of frequencies. This chapter aims to study the transient responses of various well‐known antennas over broad frequency ranges. To understand the performance of antennas over a broadband it is necessary to consider the analysis of the problem in the time domain...
This chapter presents all the various experimental results available in the literature on the propagation path loss for cellular wireless propagation systems. It provides an accurate numerical evaluation of the fields in a cellular wireless environment using a macro model based on an accurate computer program which uses the Green's function based o...
This chapter looks at the fields produced by some simple antennas and their current distributions in the frequency domain. It observes the fields produced by a Hertzian dipole, a finite sized dipole antenna, and a small loop antenna. The chapter defines the radiating regions of an antenna in terms of the near fields from the far fields and how that...
The sound source localization technique is widely applied to target detection and localization. However, the application of conventional sound source localization methods is limited in actual environment because of estimation accuracy, computational complexity and flexibility of the environment. In order to improve the sound source localization per...
In this article, we describe the notion of a cloak achieved by employing the usual composite dielectrics surrounding a metal cube, a concept that was first presented by Hwang and Chin [1]. Here, we use an optimization procedure to improve on their results and obtain a three-dimensional composite dielectric structure that can achieve a better broadb...
A parallel higher-order method of moments (HOMoM) with a newly developed reduced-communication, lower-upper (RCLU) decomposition solver is proposed in this article. The method uses 201,600 central processing unit (CPU) cores on a supercomputer located in Guangzhou, China. Our code achieves an extremely high parallel efficiency when simulating a lar...
The first objective of this article is to explain what surface plasmons and surface plasmon polaritons are. The term surface plasmons (SPs) was first coined in the middle of the 20th century to study the response of thin metal foils at petahertz frequencies when subjected to fast electron bombardment. SPs are coherent electron oscillations that exi...
Higher-order polynomials as basis functions can be adapted to deal with extremely nonuniform meshes, which range from approximately 10
<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup>
λ to 2 λ in electrical size. Thus, they are quite suitable and very flexible for modeling multiscale structures...
The higher-order method of moments (HOMoM) with a direct solver is hybridized with the multilevel fast multipole algorithm (MLFMA) given the multiscale nature of airborne antenna arrays. The integral equations of PMCHW-CFIE are solved for modeling metallic/dielectric antennas on a conducting platform. To accelerate the outer iteration between the t...
One of the objectives of this paper is to outline the differences between the internal and external resonances of an electromagnetic structure. At an internal resonance of an object there is a component of the resonant current on the structure which is real and that current does not radiate nor does it couple to the incident field. The external res...
This review paper is a sequel to an earlier paper [1] dealing with parametric methods in the context of the principle of analytic continuation and provided its relationship to reduced rank modelling using the total least squares based singular value decomposition methodology. The problem with a parametric method is that the quality of the solution...
In this article, we provide a brief history of the evolution of radar across the various regions where the technology's development occurred, often simultaneously and independently. (Note that the original term RADAR, representing "RAdio Detection And Ranging," was devised by the U.S. Navy in 1940.) We cover in detail the years from the late 19th c...
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 local plane wave in the far field, the radial component of the electric field must be negligible compared to the...
Current research on wireless radio frequency (RF) systems often makes unphysical simplifying assumptions and treats the associated signal processing and electromagnetic (EM) analyses independently, resulting in improper inclusion of the underlying physics (EM theory) of such systems and consequently leading to inaccurate and erroneous performance p...
In this paper, it is illustrated on how to carry out adaptive processing simultaneously at multiple frequencies using the same antenna array consisting of dissimilar antenna elements nonuniformly spaced and deployed in any environment. First, a transformation method is introduced to account for all non-ideal effects of an antenna deployed in a real...
A comparison of the calculated antenna patterns using near field data from measurements using a probe and without a probe is presented to illustrate the effects of the probe in the field evaluations. The equivalent magnetic current approach is used to calculate the far field using the near field data both with and without a probe in the measurement...
This document presents the application of a new electromagnetic in-house parallel EM simulator to the antenna analysis. The simulator is included in the commercial software HOBBIES. HOFEM makes use of a weak formulation based on double curl vector wave equation discretized with the higherorder isoparametric curl-conforming tetrahedral and triangula...
The objective of this paper is to reconstruct the free space radiation pattern from non-anechoic measurements in three-dimension (3D) using the impulse response both in the time and angular domains of the non-anechoic environment. This methodology could reconstruct two-dimension (2D) radiation pattern of antenna under test (AUT) characterized in no...
In electrical engineering, we obtain maximum average power from a source with some internal impedance when the connected load impedance equals the complex conjugate of the internal source impedance. This is known by the maximum power transfer theorem. Applying this theorem means that the best we can do is to distribute the source power equally betw...
The objective of this review paper is to illustrate the principle of analytic continuation and provide its relationship to reduced rank modelling using the total least squares based singular value decomposition methodology. The principles are illustrated in the different domains using the Matrix Pencil Method and the Cauchy Method for various reduc...
One of the objectives of this presentation is to illustrate how Maxwell came to his mathematical constructs of the work done before him by Oersted
, Ampère, Faraday, Gauss, and so on, into a concise and precise mathematical form. In addition, the chapter addresses two specific topics which are fundamental in engineering electromagnetic education: h...
The objective of this chapter is to illustrate that an electromagnetic macro model can accurately predict the dominant component of the propagation path loss for a cellular wireless communication. The reason a macro model can provide accurate results that agree with experiments is because the trees, buildings, and other man-made obstacles contribut...
Conventional space-time adaptive processing (STAP) is difficult to effectively suppress nonhomogeneous clutter in practical airborne phased array radar systems owing to the requirements of large independent and identically distributed training samples and the high complexity involved in the inversion of a high dimensional matrix. In order to improv...
This short expository paper provides a brief introduction to ultrawideband (UWB) theory, technology, applications, and systems with a focus on radar and brief observations on communications. The definition of UWB radar is discussed, and an experimental UWB radar (Microwave Microscope) is considered to illustrate system properties and the imaging ef...
Conventionally, the design of antennas is narrowband and little attention is paid to the phase responses of the devices as functions of frequency. Even the use of the term broadband is misleading as one essentially takes a narrow band signal and sweeps it across the band of interest. In fact, it is not necessary to pay too much attention to the pha...
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 th...
In heterogeneous networks, network selection is an important task for reconfigurable mobile devices (MDs). In the reconfigurable MD architecture that has been standardized by the European Telecommunications Standards Institute (ETSI), the network selection functionality is handled by a software component called Mobility Policy Manager (MPM). In thi...
In electrical engineering, we obtain maximum average power from a source with some internal impedance when the connected load impedance equals the complex conjugate of the internal source impedance. This is known by the maximum power transfer theorem. Applying this theorem means that the best we can do is to distribute the source power equally betw...
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 th...
This paper proposes a nondestructive technique to determine the stages of maturity of durian fruits. The presented methodology utilizes the electromagnetic scattering properties from the fruits over time for identification of the stage of maturity using its natural frequencies. Both simulation and experimental results show that the natural frequenc...
Recently, Schelkunoff integrals have been used to formulate a Green's function for analysis of radiation from a vertical electric dipole over an imperfect ground plane. Schelkunoff integrals were proved to be more suitable for numerical computation for large radial distances than the Sommerfeld integrals which are used conventionally to deal with a...
In this paper, a fast and accurate interpolation algorithm is proposed to reconstruct the high resolution amplitude only frequency domain response such as radar cross section and antenna radiation patterns from sparse and nonuniform samples based on the Cauchy method. For the Cauchy method, the amplitude only system frequency response is represente...
Subarray partition is indispensable in large phased array radar system for reducing the manufacturing cost as well as realizing the system potentiality. The optimization of subarray partition for large planar phased array radar according to weighted K-means clustering method is mainly investigated in this paper. Based on the excitation matching tec...
In In this presentation, a source reconstruction on a surface close to the antenna of interest is proposed to obtain the set of equivalent currents representing the forward and backward radiation fields of an antenna whose near field pattern has been measured. Once these equivalent sources are determined, the electromagnetic fields at any aspect an...
In the adaptive beamforming methodology used in the signal processing community, typically the adaptive weights are connected to each one of the antenna elements in the array and the processing information is generated over time, as the correlation matrix of the data needs to be formed. In the electromagnetic community however, the procedure is to...
The tutorial is split into 2 components: broadband theory/technology/systems and radar-communication interaction. For the broadband component, we will discuss the underlying theory, component technology, and some systems, with a focus on the two ultrawideband (UWB) application areas (radar and communication systems) in light of recent interest in U...
In this paper a conceptual method to diagnose and remotely monitor vital cardiac signs in patients is proposed. The proposed methodology utilizes technology with digital probing diagnostic tools and current wireless systems to monitor the health conditions of patients without direct physical intervention of physicians. The data could also be used t...
A precis of spectrum congestion among RF users is given, with a focus on radar-communication co-existence. In particular, some recent efforts to mitigate this interference are briefly discussed, and intimations of requisite research and possible ways to achieve spectral harmony are provided.
In this paper, we show how to eliminate shadow fading in cellular wireless system and discuss the main reason for such a phenomenon. One can deploy the transmitting antenna closer to the ground. In that case, the region of the variation in the field strength (shadow fading region) would be quite small and the field strength will decay monotonically...
The purpose of this article is to demonstrate that the conventional S-parameters cannot be applied to devices having complex characteristic impedances as in some cases the reflection coefficient can be greater than 1 even when terminated by a passive conjugate load for maximum power transfer. This is particularly pertinent for antenna problems. Als...
The method of mode matching (MM) is used to construct ideal waveports in the context of the method of moments (MoM). The waveports can provide not only excitations as sources but also perfectly matched loads for traveling-wave slotted waveguide antennas. Additionally, the application of the higher order basis functions (HOBs) in MoM significantly r...
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 Ch...
In this paper, we study the performance of the Electrically Small Antennas (ESAs) versus larger antennas in both transmitting and receiving modes. We conclude that the ESAs perform well compared to larger antennas under matched conditions where the input power to the antenna is real (input power is S = V in I in , V in and I in are the phasor domai...
A new approach to reconstructing antenna far-field patterns from the missing part of the pattern is presented in this paper. The antenna far-field pattern can be reconstructed by utilizing the iterative Hilbert transform, which is based on the relationship between the real and imaginary part of the Hilbert transform. A moving average filter is used...
This paper presents the effect of broadband matching in simultaneous information and power transfer along with an implementation. The narrowband characteristic of antennas has limited the applications of simultaneous information and power transfer. The performance improvements in terms of channel capacity and power delivery under broadband matching...
A new boundary integral method for solving the general Helmholtz equation has been developed starting from the frequency independent Laplace's equation. The new formulation is based on the Method of Moments solution of Laplace's equation. The main feature of this new formulation is that the boundary conditions are satisfied independent of the regio...
To isolate regions in the time domain it is necessary to carry out wideband measurements. Typically, the resolution in the time domain is limited by the Rayleigh criteria where the resolution of artifacts in the time domain is inversely proportional to the amount of bandwidth in the measured data. However, if we use a model based parameter estimati...
In electromagnetics, time reversal was first examined in the fifties of the twentieth century. Whereas in acoustics, time reversal was first experimented in the nineties. In the current literature on electromagnetics, antennas and propagation and wireless communications, time reversal is frequently referred to as a technology that first appeared in...
The objective of this paper is to investigate a methodology, which can extract approximate results for the free space radiation pattern from data obtained in a non-anechoic environment. Using an impulse response in the angular domain at a single frequency of the non-anechoic environment, the free space pattern of the device under test is estimated....
An electromagnetic in-house parallel EM solver for RCS computation of complex target is presented in this paper. The solver makes use of a weak formulation based on double curl vector wave equation discretized with the higher-order isoparametric curl-conforming tetrahedral finite element rigorous implementations of Ne[acute ]de[acute ]lec first fam...
Two patch resonator filters, namely Type I and Type II, are designed using a slot composed of multiple circular sectors. The filters operate in the 2.4-2.48 GHz wireless local area network (WLAN) frequency. The measured 3 dB insertion loss bandwidth of the filters covers the whole WLAN band. The stopband of the Type II filter is below 2.18 GHz and...
The problem of identifying unripe fruits using a non-destructive evaluation methodology is of great interest. In this paper the natural frequency estimation methodology described by the singularity expansion method (SEM) is used to evaluate the state of maturity of the mangosteen fruit using a non-destructive classification technique. The methodolo...
Closed-form expressions for the approximation of frequency variations of per-unit-length resistance and inductance of microstrip transmission lines are presented. The provided expressions guarantee causality of the time-domain response. They are valid from dc up to the highest frequencies for which the quasi-static analysis of microstrip transmissi...
The efficiency of a parallel higher-order method of moments is illustrated using up to 4096 CPU cores on a supercomputer. The scattering problems solved include the analysis from two full scale airplanes and the radiation problems include performance of a microstrip patch phased array antenna mounted on an airplane. Both the scattering and radiatio...
The objective of this presentation is to illustrate the accuracy of the Schelkunoff formulation over the Sommerfeld solution for a vertical electric dipole radiating over an imperfect ground. In an earlier paper, the alternate form of the Sommerfeld Green's function developed by Schelkunoff was presented (Schelkunoff, 1943 and Dyab, 2013). Here we...
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 actual drive tests to assess the coverage area of a base station for a given cell and thus evaluate the QOS. In a drive test...
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 pape...
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 pape...
This paper presents the method of creating the general models of base-station antennas which are suitable for the common full-wave electromagnetic (EM) field solvers. For those EM simulators based on high frequency or asymptotic methods, the antenna models can simply be imported by the manufacturer data file. However, it is not so common in most of...
This paper illustrates a method to carry out adaptive processing simultaneously at multiple frequencies using the same antenna array located over imperfect ground planes. First, it is shown how to transform an array situated over an imperfect ground to a uniformly spaced array of point radiators. Then, a direct data domain least squares (D3LS) meth...
The performance of adaptive beamforming degrades in presence of signal model mismatches. In particular, when the desired signal is present in training snapshots, the adaptive beamforming is quite sensitive to desired signal steering vector mismatch. Therefore, a robust adaptive beamforming for actual system is proposed based on the reconstruction o...
The two historical topics that are so fundamental in electromagnetic education are addressed in this talk. It is not well recognized that Maxwell reached the conclusion light was electromagnetic in nature before he wrote his 20 equations which were reduced to the four that we use today by Hertz and Heaviside. In addition, Maxwell did not have the b...