IEEE Transactions on Antennas and Propagation, 2008
The characteristic basis function method (CBFM) has been hybridized with the adaptive cross appro... more The characteristic basis function method (CBFM) has been hybridized with the adaptive cross approximation (ACA) algorithm to construct a reduced matrix equation in a time-efficient manner and to solve electrically large antenna array problems in-core, with a solve time orders of magnitude less than those in the conventional methods. Various numerical examples are presented that demonstrate that the proposed method has a very good accuracy, computational efficiency and reduced memory storage requirement. Specifically, we analyze large 1-D and 2-D arrays of electrically interconnected tapered slot antennas (TSAs). The entire computational domain is subdivided into many smaller subdomains, each of which supports a set of characteristic basis functions (CBFs). We also present a novel scheme for generating the CBFs that do not conform to the edge condition at the truncated edge of each subdomain, and provide a minor overlap between the CBFs in adjacent subdomains. As a result, the CBFs preserve the continuity of the surface current across the subdomain interfaces, thereby circumventing the need to use separate ldquoconnectionrdquo basis functions.
IEEE Antennas and Propagation Society International Symposium. Transmitting Waves of Progress to the Next Millennium. 2000 Digest. Held in conjunction with: USNC/URSI National Radio Science Meeting (Cat. No.00CH37118)
2011 IEEE International Symposium on Antennas and Propagation (APSURSI), 2011
This paper considers the four most common equivalent network models of a single-layer circuit-ana... more This paper considers the four most common equivalent network models of a single-layer circuit-analog absorber, and demonstrates that the series RLC configuration performs superior to the others. With proper selection of the component values, this configuration can realize two resonances, which lead to an overall wideband absorption. Based on this finding, we derive closed-form design expressions for an optimally thin and wideband single-layer absorber. To demonstrate the superiority of the series RLC absorber, a design example has been provided where 10-dB bandwidth of 128% is obtained through a single-layer absorber whose thickness is less than λ/11 at the lowest frequency of absorption.
Self-complementary antennas are based on the Babinet principle in which electric and magnetic fie... more Self-complementary antennas are based on the Babinet principle in which electric and magnetic fields are interchanged (duality) with the structure invariant to this transformation. This paper develops self-complementary structures from the electric and magnetic parts of a complex potential as used in conformal transformation. This leads to various geometries of electrically small impedance sheets with relatively simply calculable admittance properties. These are also related to the impedance properties of some TEM transmission-line structures (cylindrical and conical). The use of conformal and stereographic transformations allows one to generalize self-complementary structures on planes and spheres to structures having the self-complementary admittance properties without the restricted geometrical symmetries.
IEEE Antennas and Propagation Society International Symposium (IEEE Cat. No.02CH37313)
It is well known that the genetic algorithms (GAs) fall under a special category of optimization ... more It is well known that the genetic algorithms (GAs) fall under a special category of optimization schemes that are robust stochastic search methods based on the principles of natural selection, and that they are particularly effective in searching for global maxima in a multidimensional and multi-modal functional domain. The GAs simultaneously process a population of points in the optimization space,
AnalyseLes auteurs présentent une méthode pour augmenter le gain d’une grande antenne Cassegrain ... more AnalyseLes auteurs présentent une méthode pour augmenter le gain d’une grande antenne Cassegrain pour station terrienne et le rendre comparable à celui d’une antenne à deux réflecteurs de forme optimale. Cette méthode consiste à modifier uniquement le sous-réflecteur (ou réflecteur secondaire) ou à introduire une source d’illumination à sous-réflecteurs pour un paraboloïde. On synthétise alors un couple de sous-réflecteurs à alimentation décalée, ce qui permet de corriger la distribution en amplitude sur l’ouverture du grand paraboloïde et d’obtenir ainsi un gain élevé. Cette méthode de synthèse est basée sur une formulation approchée où l’énergie (au sens de l’optique géométrique) est rayonnée à partir d’un sous-réflecteur puis d’un deuxième grand réflecteur réfléchissant une distribution uniforme en phase. Dans le cas présenté ici (antenne à deux réflecteurs à alimentation décalée), le champ électromagnétique, après deux réflexions, se présente sous la forme d’une onde sphérique éclairant, à son tour, soit un hyperboloïde, soit directement un paraboloïde. D’excellents résultats sont présentés pour la synthèse approchée de ces sources d’illumination.AbstractA potentially economic method for upgrading the gain of the large earth reflector antenna Cassegrain system to a gain comparable to that obtainable with a dualshaped reflector antenna system is presented herein. It involves a redesign of only the subreflector portion of a Cassegrain antenna or the introduction of a subreflector feed system for a paraboloid. A pair of offset subreflectors are synthesized which will give a controllable high gain amplitude distribution in the aperture of the large paraboloid. The synthesis method that is used is based on an approximate formulation for an offset dual shaped high gain antenna where the geometrical optics energy was scattered from a subreflector and then from a second large reflector which reflected a uniform phase distribution. In the present offset dual shaped subreflector (DSS) antenna, the second reflection is from a smaller subreflector and it scatters a spherical wave that feeds a hyperboloid or feeds a large paraboloid directly. Excellent results are shown for the approximate synthesis of the DSS.
Abstract : This report studies the application of spectral domain analysis to the problem of the ... more Abstract : This report studies the application of spectral domain analysis to the problem of the high-frequency diffraction of electromagnetic waves. The basic formulation of the spectral approach is first summarized and then applied in a unified fashion to the important problems of the non-uniform illumination of a half-plane and staggered parallel planes. Special attempts are made to analytically determine the fields at the shadow boundaries and numerically evaluate them in the transition regions. Comparison is made with other high-frequency asymptotic techniques and some unique conclusions are obtained. Furthermore, it is shown that the important task of testing and improving high-frequency solutions can be accomplished by employing the Fourier transform of the integral equation for the surface current and using Galerkin's method in the spectral domain. Some examples of this approach are also included.
IEEE Antennas and Propagation Society International Symposium. 2001 Digest. Held in conjunction with: USNC/URSI National Radio Science Meeting (Cat. No.01CH37229)
IEEE Antennas and Propagation Society International Symposium. 1998 Digest. Antennas: Gateways to the Global Network. Held in conjunction with: USNC/URSI National Radio Science Meeting (Cat. No.98CH36194)
High gain antennas are often employed in communication systems to meet specific coverage requirem... more High gain antennas are often employed in communication systems to meet specific coverage requirements. To achieve high gain characteristics, one typically uses an array of radiating elements, e.g., active patch antennas, vertical dipoles, etc. By carefully choosing the excitation of each element, and their spacing, one can obtain certain desired gain characteristics, such as a high and narrow main beam with low sidelobes. The article introduces the concept of high gain dipole antennas that are realized by inserting lumped LC loads along the dipole. Also, in an effort to maximize the efficiency of the antenna, we make the loads entirely lossless
2007 International Conference on Electromagnetics in Advanced Applications, 2007
The objective of this paper is to describe two parallel algorithms, one in the frequency and the ... more The objective of this paper is to describe two parallel algorithms, one in the frequency and the other in the time domain, both of which have been designed for solving large problems on parallel computing platforms.
2008 IEEE Antennas and Propagation Society International Symposium, 2008
In this work, we have investigated the mechanism of performance enhancement of a dipole antenna l... more In this work, we have investigated the mechanism of performance enhancement of a dipole antenna located above a ground plane, and covered by a dielectric EBG superstrate. We show that the maximum enhancement in the received power can be up to 9.3 dB for the composite. We have gained considerable insight into the mechanism of directivity enhancement that should help us with future designs.
IEEE Antennas and Propagation Society International Symposium. 1998 Digest. Antennas: Gateways to the Global Network. Held in conjunction with: USNC/URSI National Radio Science Meeting (Cat. No.98CH36194)
IEEE Transactions on Antennas and Propagation, 2008
The characteristic basis function method (CBFM) has been hybridized with the adaptive cross appro... more The characteristic basis function method (CBFM) has been hybridized with the adaptive cross approximation (ACA) algorithm to construct a reduced matrix equation in a time-efficient manner and to solve electrically large antenna array problems in-core, with a solve time orders of magnitude less than those in the conventional methods. Various numerical examples are presented that demonstrate that the proposed method has a very good accuracy, computational efficiency and reduced memory storage requirement. Specifically, we analyze large 1-D and 2-D arrays of electrically interconnected tapered slot antennas (TSAs). The entire computational domain is subdivided into many smaller subdomains, each of which supports a set of characteristic basis functions (CBFs). We also present a novel scheme for generating the CBFs that do not conform to the edge condition at the truncated edge of each subdomain, and provide a minor overlap between the CBFs in adjacent subdomains. As a result, the CBFs preserve the continuity of the surface current across the subdomain interfaces, thereby circumventing the need to use separate ldquoconnectionrdquo basis functions.
IEEE Antennas and Propagation Society International Symposium. Transmitting Waves of Progress to the Next Millennium. 2000 Digest. Held in conjunction with: USNC/URSI National Radio Science Meeting (Cat. No.00CH37118)
2011 IEEE International Symposium on Antennas and Propagation (APSURSI), 2011
This paper considers the four most common equivalent network models of a single-layer circuit-ana... more This paper considers the four most common equivalent network models of a single-layer circuit-analog absorber, and demonstrates that the series RLC configuration performs superior to the others. With proper selection of the component values, this configuration can realize two resonances, which lead to an overall wideband absorption. Based on this finding, we derive closed-form design expressions for an optimally thin and wideband single-layer absorber. To demonstrate the superiority of the series RLC absorber, a design example has been provided where 10-dB bandwidth of 128% is obtained through a single-layer absorber whose thickness is less than λ/11 at the lowest frequency of absorption.
Self-complementary antennas are based on the Babinet principle in which electric and magnetic fie... more Self-complementary antennas are based on the Babinet principle in which electric and magnetic fields are interchanged (duality) with the structure invariant to this transformation. This paper develops self-complementary structures from the electric and magnetic parts of a complex potential as used in conformal transformation. This leads to various geometries of electrically small impedance sheets with relatively simply calculable admittance properties. These are also related to the impedance properties of some TEM transmission-line structures (cylindrical and conical). The use of conformal and stereographic transformations allows one to generalize self-complementary structures on planes and spheres to structures having the self-complementary admittance properties without the restricted geometrical symmetries.
IEEE Antennas and Propagation Society International Symposium (IEEE Cat. No.02CH37313)
It is well known that the genetic algorithms (GAs) fall under a special category of optimization ... more It is well known that the genetic algorithms (GAs) fall under a special category of optimization schemes that are robust stochastic search methods based on the principles of natural selection, and that they are particularly effective in searching for global maxima in a multidimensional and multi-modal functional domain. The GAs simultaneously process a population of points in the optimization space,
AnalyseLes auteurs présentent une méthode pour augmenter le gain d’une grande antenne Cassegrain ... more AnalyseLes auteurs présentent une méthode pour augmenter le gain d’une grande antenne Cassegrain pour station terrienne et le rendre comparable à celui d’une antenne à deux réflecteurs de forme optimale. Cette méthode consiste à modifier uniquement le sous-réflecteur (ou réflecteur secondaire) ou à introduire une source d’illumination à sous-réflecteurs pour un paraboloïde. On synthétise alors un couple de sous-réflecteurs à alimentation décalée, ce qui permet de corriger la distribution en amplitude sur l’ouverture du grand paraboloïde et d’obtenir ainsi un gain élevé. Cette méthode de synthèse est basée sur une formulation approchée où l’énergie (au sens de l’optique géométrique) est rayonnée à partir d’un sous-réflecteur puis d’un deuxième grand réflecteur réfléchissant une distribution uniforme en phase. Dans le cas présenté ici (antenne à deux réflecteurs à alimentation décalée), le champ électromagnétique, après deux réflexions, se présente sous la forme d’une onde sphérique éclairant, à son tour, soit un hyperboloïde, soit directement un paraboloïde. D’excellents résultats sont présentés pour la synthèse approchée de ces sources d’illumination.AbstractA potentially economic method for upgrading the gain of the large earth reflector antenna Cassegrain system to a gain comparable to that obtainable with a dualshaped reflector antenna system is presented herein. It involves a redesign of only the subreflector portion of a Cassegrain antenna or the introduction of a subreflector feed system for a paraboloid. A pair of offset subreflectors are synthesized which will give a controllable high gain amplitude distribution in the aperture of the large paraboloid. The synthesis method that is used is based on an approximate formulation for an offset dual shaped high gain antenna where the geometrical optics energy was scattered from a subreflector and then from a second large reflector which reflected a uniform phase distribution. In the present offset dual shaped subreflector (DSS) antenna, the second reflection is from a smaller subreflector and it scatters a spherical wave that feeds a hyperboloid or feeds a large paraboloid directly. Excellent results are shown for the approximate synthesis of the DSS.
Abstract : This report studies the application of spectral domain analysis to the problem of the ... more Abstract : This report studies the application of spectral domain analysis to the problem of the high-frequency diffraction of electromagnetic waves. The basic formulation of the spectral approach is first summarized and then applied in a unified fashion to the important problems of the non-uniform illumination of a half-plane and staggered parallel planes. Special attempts are made to analytically determine the fields at the shadow boundaries and numerically evaluate them in the transition regions. Comparison is made with other high-frequency asymptotic techniques and some unique conclusions are obtained. Furthermore, it is shown that the important task of testing and improving high-frequency solutions can be accomplished by employing the Fourier transform of the integral equation for the surface current and using Galerkin's method in the spectral domain. Some examples of this approach are also included.
IEEE Antennas and Propagation Society International Symposium. 2001 Digest. Held in conjunction with: USNC/URSI National Radio Science Meeting (Cat. No.01CH37229)
IEEE Antennas and Propagation Society International Symposium. 1998 Digest. Antennas: Gateways to the Global Network. Held in conjunction with: USNC/URSI National Radio Science Meeting (Cat. No.98CH36194)
High gain antennas are often employed in communication systems to meet specific coverage requirem... more High gain antennas are often employed in communication systems to meet specific coverage requirements. To achieve high gain characteristics, one typically uses an array of radiating elements, e.g., active patch antennas, vertical dipoles, etc. By carefully choosing the excitation of each element, and their spacing, one can obtain certain desired gain characteristics, such as a high and narrow main beam with low sidelobes. The article introduces the concept of high gain dipole antennas that are realized by inserting lumped LC loads along the dipole. Also, in an effort to maximize the efficiency of the antenna, we make the loads entirely lossless
2007 International Conference on Electromagnetics in Advanced Applications, 2007
The objective of this paper is to describe two parallel algorithms, one in the frequency and the ... more The objective of this paper is to describe two parallel algorithms, one in the frequency and the other in the time domain, both of which have been designed for solving large problems on parallel computing platforms.
2008 IEEE Antennas and Propagation Society International Symposium, 2008
In this work, we have investigated the mechanism of performance enhancement of a dipole antenna l... more In this work, we have investigated the mechanism of performance enhancement of a dipole antenna located above a ground plane, and covered by a dielectric EBG superstrate. We show that the maximum enhancement in the received power can be up to 9.3 dB for the composite. We have gained considerable insight into the mechanism of directivity enhancement that should help us with future designs.
IEEE Antennas and Propagation Society International Symposium. 1998 Digest. Antennas: Gateways to the Global Network. Held in conjunction with: USNC/URSI National Radio Science Meeting (Cat. No.98CH36194)
Uploads
Papers by Raj Mittra