Sadasiva Rao - Academia.edu (original) (raw)
Papers by Sadasiva Rao
In this work, we present a new power series solution procedure to obtain induced currents and sca... more In this work, we present a new power series solution procedure to obtain induced currents and scattered fields on a large conducting body due to a plane wave incidence. The procedure follows standard method of moments approach yet is applicable to electrically large problems. The first step involves approximating the given structure via standard geometrical discretization and defining the conventional basis functions to approximate the induced current. The next step involves gathering the total number of basis functions into a small number of groups thereby casting the moment matrix into a collection of submatrices representing self and mutual interaction between the groups. Next, the procedure involves eliminating the interaction of two immediate neighbors on any selected group. This process results in a diagonally-dominant moment matrix assuming the group size is sufficiently large. Also the procedure sets the matrix blocks residing on either side of the diagonal block to zero. Th...
IEEE Transactions on Antennas and Propagation, 1982
The method of steepest descent is applied to the solution of electrostatic problems. The relation... more The method of steepest descent is applied to the solution of electrostatic problems. The relationship between this method and the Rayleigh-Ritz, Galerkin's, and the method of least squares is outlined. Also, explicit error formulas are given for the rate of convergence for this method. It is shown that this method is also suitable for solving singular operator equations. In that case this method monotonically converges to the solution with minimum norm. Finally, it is shown that the technique yields as a by-product the smallest eigenvalue of the operator in the finite dimensional space in which the problem is solved. Numerical results are presented only for the electrostatic case to illustrate the validity of this procedure which show excellent agreement with other available data.
IEEE Transactions on Antennas and Propagation, 1986
The Applied Computational Electromagnetics Society Journal (ACES)
In this paper, we propose a new multi-level power series solution method for solving a large surf... more In this paper, we propose a new multi-level power series solution method for solving a large surface and volume electric field integral equation-based H-Matrix. The proposed solution method converges in a fixed number of iterations and is solved at each level of the H-Matrix computation. The solution method avoids the computation of a full matrix, as it can be solved independently at each level, starting from the leaf level. Solution at each level can be used as the final solution, thus saving the matrix computation time for full H-Matrix. The paper shows that the leaf level matrix computation and solution with power series gives as accurate results as the full H-Matrix iterative solver method. The method results in considerable savings time and memory savings compared to the H-Matrix iterative solver. Further, the proposed method retains the O(NlogN) solution complexity.
A new transformation for evaluating Sommerfeld integrals is derived here when the path is deforme... more A new transformation for evaluating Sommerfeld integrals is derived here when the path is deformed in the upper half of the complex plane. This transformation has the feature that as the lateral separation ρ → ∞, the argument of the Bessel function diminishes. It is argued that this approach shall facilitate much efficient calculation of Sommerfeld integrals.
2010 IEEE Antennas and Propagation Society International Symposium, 2010
Directed by Sadasiva M. Rao Smart antennas present a promising solution to the present day capaci... more Directed by Sadasiva M. Rao Smart antennas present a promising solution to the present day capacity and coverage shortage in mobile wireless communications. These intelligent antennas when used at the base station can avoid a lot of interference by transmitting and receiving signals only in desired directions. Circular array antennas have gained popularity among various antenna configurations used for direction agile applications. The purpose of this thesis is to design a planar circular array antenna for base stations in mobile wireless communication systems. The antenna could be electronically steered to give a complete 360 coverage around the base station. The model was created using FEKO Suite 5.4, a Method of Moments (MoM) based electromagnetic simulation software. Particle Swarm Optimization algorithm was applied to maximize the gain of the antenna in a single azimuth direction. Ideal dimensions for the antenna structure were obtained from the optimization process. v The designed antenna was fabricated and tested in an anechoic chamber to verify its radiation characteristics. The experimental results were found to be in good agreement with the simulation results. An improved design configuration was simulated for future development of this array antenna.
Microwave and Optical Technology Letters, 2012
In this work, we present a new iterative method to solve electromagnetic field problems using the... more In this work, we present a new iterative method to solve electromagnetic field problems using the method of moments formulation.The new method requires much fewer mathematical operations per iteration when compared to other available methods. Further, the method can easily handle multiple right‐hand side vectors much the same way as direct solution techniques. Several numerical examples are presented to illustrate the efficiency and accuracy of the new method. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2042–2046, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27023
International Journal of Microwave and Millimeter-Wave Computer-Aided Engineering, 1992
Arbitrarily shaped microstrip patch antennas have been analyzed for resonant frequency, input imp... more Arbitrarily shaped microstrip patch antennas have been analyzed for resonant frequency, input impedance, and radiation patterns. The segmentation technique and the cavity model have been used for this purpose. The usefulness and the accuracy of the method are shown through comparison with experimental results for a rectangular ring antenna. The agreement is seen to be very good. The method appears to be more efficient compared to those reported so far for arbitrary shapes. Moreover, feed reactance is built into the analysis. The method presented here can also be used to analyze microstrip antennas with various types of loadings, e.g., shorting pins, matched loads, etc.
IEEE Transactions on Microwave Theory and Techniques, 1997
In this paper, it is shown that Cauchy's method can be used effectively to interpolate/extrapolat... more In this paper, it is shown that Cauchy's method can be used effectively to interpolate/extrapolate narrow-band system responses. The given information can either be theoretical datapoints or measured experimental data over a band. For theoretical data extrapolation or interpolation, the sampled values of the function and, optionally, a few of its derivatives have been used to reconstruct the function. For measured data, only measured values of the parameter are used to create broadband information from limited data as derivative information is too noisy. Cauchy's method assumes that the parameter to be extrapolated/interpolated, as a function of frequency, is a ratio of two polynomials. The problem is to determine the order of the polynomials and the coefficients therein. The method of total least squares (TLS) has been used to solve the resulting matrix equation involving the coefficients of the polynomials. Typical numerical results have been presented to show that reliable interpolation/extrapolation can be done for various system responses.
IEEE Transactions on Microwave Theory and Techniques, 1990
Two techniques are presented for the analysis of electromagnetic radiation and scattering from fi... more Two techniques are presented for the analysis of electromagnetic radiation and scattering from finite microstrip structures. The two techniques are based on two different formulations, viz. the volume-surface and surface-surface formulations. In the volume-surface formulation the finite-sized dielectric is replaced by an equivalent volume polarization current whereas the conducting plates are replaced by equivalent surface currents. For the surface-surface formulation the surface covering the dielectric volume is replaced by equivalent electric and magnetic currents and the conducting plates by surface electric currents. Both techniques can be utilized for the analysis of arbitrarily shaped finite microstrip structures. The techniques are quite accurate, and they are utilized to validate each other. Typical numerical results are presented to demonstrate the agreement between these two solution techniques
IEEE Transactions on Microwave Theory and Techniques, 1997
A new numerical procedure is developed for the solution of the electric field integral equation (... more A new numerical procedure is developed for the solution of the electric field integral equation (EFIE) for arbitraryshaped microstrip structures. This approach is superior over conventional EFIE techniques particularly in the low-frequency region or where the structure to be analyzed is electrically small. A pair of new basis functions is presented which are essential to the solution in the entire frequency range of interest. The new basis functions decompose the surface current density into divergenceless and curl-free parts which essentially get decoupled at the very low end of the frequency spectrum. Typical numerical results are presented for certain examples to illustrate the difference in the results between the two methods.
IEEE Transactions on Antennas and Propagation, 2012
A true domain decomposition method to obtain numerical solution involving electrically large bodi... more A true domain decomposition method to obtain numerical solution involving electrically large bodies using the method of moments (MOM) formulation is the subject matter of the present work. The electrically large body is initially divided into smaller sub-structures. By defining a set of new basis functions adaptively, utilizing the primary basis functions, a solution scheme is developed which completely eliminates the interaction of one substructure with the rest of the body. This procedure enables to solve each substructure independently and involves no iterative solution as a final step. The present method is conceptually simple and applicable to any MOM solution. Further, the method can easily handle multiple right-hand side vectors much the same way as the conventional MOM solution. A few representative numerical examples are presented to illustrate the applicability of the new method.
IEEE Transactions on Antennas and Propagation, 1993
Lengthy comments are offered on some remarks made in the paper by D.A. Vechinski and S.M. Rao (se... more Lengthy comments are offered on some remarks made in the paper by D.A. Vechinski and S.M. Rao (see ibid., vol.40, no.6, p.661-5, June 1992) regarding the solution procedure described by B.P. Rynne (1991). Vechinski and Rao offer arguments in rebuttal
IEEE Transactions on Antennas and Propagation, 2002
In this work, we present the application of specially constructed adapti¨e basis functions to gen... more In this work, we present the application of specially constructed adapti¨e basis functions to generate a diagonal matrix in the method-of-moments solution procedure for the calculation of a scattered electromagnetic field from arbitrarily shaped two-dimensional cylinders excited by a trans¨erse electric incident electromagnetic wa¨e. Se¨eral numerical examples are also presented to¨alidate the new method.
IEEE Transactions on Antennas and Propagation, 2010
We present a new method of moments solution procedure for calculating electromagnetic scattering ... more We present a new method of moments solution procedure for calculating electromagnetic scattering and radiation from conductor/dielectric composite structures. The solution is obtained using triangular patch modeling and a recently developed pair of mutually orthogonal pulse basis functions to represent the equivalent currents J and M. The pulse basis functions are defined with respect to the edges in the triangulated model and partially spread over the triangles connected to the edge. The orthogonality of the basis functions allows the development of stable solutions for all formulations and configurations investigated. A set of numerical results is presented that illustrates the efficacy of the present approach.
IEEE Transactions on Antennas and Propagation, 1991
Page 1. 1034 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 39, NO. 7, JULY 1991 .sin@,P,&am... more Page 1. 1034 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 39, NO. 7, JULY 1991 .sin@,P,'(cose) ~T[P,'(cos8)]2sinBd~ (23) 0 and E,(r,8,4) = 0. Equation (23) expresses the radiation field components at any point outside the spherical body. ...
IEEE Transactions on Antennas and Propagation, 2002
Page 1. IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 50, NO. 12, DECEMBER 2002 1831 Numeri... more Page 1. IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 50, NO. 12, DECEMBER 2002 1831 Numerical Solution of Time Domain Integral Equations for Arbitrarily Shaped Conductor/Dielectric Composite Bodies ...
IEEE Transactions on Antennas and Propagation, 2011
In this work, a new numerical procedure is developed to apply the well-known method of moments (M... more In this work, a new numerical procedure is developed to apply the well-known method of moments (MoM) formulation to electrically large conducting bodies of arbitrary shape. The numerical procedure involves developing a combination of subdomain-entire domain basis functions which result in a sparse moment matrix as opposed to a full matrix in the traditional method. Moreover, the zeros in the MoM matrix are precisely at the same locations where one would have encountered the most significant values. The solution of the new matrix may be obtained using the simple Gauss-Seidel iterative procedure with only two or three iterations. All the traditional advantages of the MoM procedure are retained including the solution for multiple incident fields. Several numerical results are presented to illustrate the validity of the new approach. Index Terms-Fast method, large-body problems, method of moments (MoM), RWG basis.
IEEE Transactions on Antennas and Propagation, 1997
In this paper, we use the matrix pencil approach to extrapolate time-domain responses from three-... more In this paper, we use the matrix pencil approach to extrapolate time-domain responses from three-dimensional (3-D) conducting objects that arise in the numerical solution of electromagnetic field problems. By modeling the time functions as a sum of complex exponentials, we can eliminate some of the instabilities that arise in late times for the electric-field integral equation in the time domain. However, this method can also be utilized for extending the responses obtained using a finitedifference time-domain (FDTD) formulation.
IEEE Microwave and Guided Wave Letters, 1995
In this work, we utilize the finite element technique to open region problems in conjunction with... more In this work, we utilize the finite element technique to open region problems in conjunction with the truncation condition based on the measured equation of invariance (MEI) concept. The major advantage of the present scheme is a significant reduction in the number of unknowns while retaining the sparsity of the generating matrix.~pical numerical results are presented for the solution of Laplace's equation to illustrate the accuracy of the technique.
In this work, we present a new power series solution procedure to obtain induced currents and sca... more In this work, we present a new power series solution procedure to obtain induced currents and scattered fields on a large conducting body due to a plane wave incidence. The procedure follows standard method of moments approach yet is applicable to electrically large problems. The first step involves approximating the given structure via standard geometrical discretization and defining the conventional basis functions to approximate the induced current. The next step involves gathering the total number of basis functions into a small number of groups thereby casting the moment matrix into a collection of submatrices representing self and mutual interaction between the groups. Next, the procedure involves eliminating the interaction of two immediate neighbors on any selected group. This process results in a diagonally-dominant moment matrix assuming the group size is sufficiently large. Also the procedure sets the matrix blocks residing on either side of the diagonal block to zero. Th...
IEEE Transactions on Antennas and Propagation, 1982
The method of steepest descent is applied to the solution of electrostatic problems. The relation... more The method of steepest descent is applied to the solution of electrostatic problems. The relationship between this method and the Rayleigh-Ritz, Galerkin's, and the method of least squares is outlined. Also, explicit error formulas are given for the rate of convergence for this method. It is shown that this method is also suitable for solving singular operator equations. In that case this method monotonically converges to the solution with minimum norm. Finally, it is shown that the technique yields as a by-product the smallest eigenvalue of the operator in the finite dimensional space in which the problem is solved. Numerical results are presented only for the electrostatic case to illustrate the validity of this procedure which show excellent agreement with other available data.
IEEE Transactions on Antennas and Propagation, 1986
The Applied Computational Electromagnetics Society Journal (ACES)
In this paper, we propose a new multi-level power series solution method for solving a large surf... more In this paper, we propose a new multi-level power series solution method for solving a large surface and volume electric field integral equation-based H-Matrix. The proposed solution method converges in a fixed number of iterations and is solved at each level of the H-Matrix computation. The solution method avoids the computation of a full matrix, as it can be solved independently at each level, starting from the leaf level. Solution at each level can be used as the final solution, thus saving the matrix computation time for full H-Matrix. The paper shows that the leaf level matrix computation and solution with power series gives as accurate results as the full H-Matrix iterative solver method. The method results in considerable savings time and memory savings compared to the H-Matrix iterative solver. Further, the proposed method retains the O(NlogN) solution complexity.
A new transformation for evaluating Sommerfeld integrals is derived here when the path is deforme... more A new transformation for evaluating Sommerfeld integrals is derived here when the path is deformed in the upper half of the complex plane. This transformation has the feature that as the lateral separation ρ → ∞, the argument of the Bessel function diminishes. It is argued that this approach shall facilitate much efficient calculation of Sommerfeld integrals.
2010 IEEE Antennas and Propagation Society International Symposium, 2010
Directed by Sadasiva M. Rao Smart antennas present a promising solution to the present day capaci... more Directed by Sadasiva M. Rao Smart antennas present a promising solution to the present day capacity and coverage shortage in mobile wireless communications. These intelligent antennas when used at the base station can avoid a lot of interference by transmitting and receiving signals only in desired directions. Circular array antennas have gained popularity among various antenna configurations used for direction agile applications. The purpose of this thesis is to design a planar circular array antenna for base stations in mobile wireless communication systems. The antenna could be electronically steered to give a complete 360 coverage around the base station. The model was created using FEKO Suite 5.4, a Method of Moments (MoM) based electromagnetic simulation software. Particle Swarm Optimization algorithm was applied to maximize the gain of the antenna in a single azimuth direction. Ideal dimensions for the antenna structure were obtained from the optimization process. v The designed antenna was fabricated and tested in an anechoic chamber to verify its radiation characteristics. The experimental results were found to be in good agreement with the simulation results. An improved design configuration was simulated for future development of this array antenna.
Microwave and Optical Technology Letters, 2012
In this work, we present a new iterative method to solve electromagnetic field problems using the... more In this work, we present a new iterative method to solve electromagnetic field problems using the method of moments formulation.The new method requires much fewer mathematical operations per iteration when compared to other available methods. Further, the method can easily handle multiple right‐hand side vectors much the same way as direct solution techniques. Several numerical examples are presented to illustrate the efficiency and accuracy of the new method. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2042–2046, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27023
International Journal of Microwave and Millimeter-Wave Computer-Aided Engineering, 1992
Arbitrarily shaped microstrip patch antennas have been analyzed for resonant frequency, input imp... more Arbitrarily shaped microstrip patch antennas have been analyzed for resonant frequency, input impedance, and radiation patterns. The segmentation technique and the cavity model have been used for this purpose. The usefulness and the accuracy of the method are shown through comparison with experimental results for a rectangular ring antenna. The agreement is seen to be very good. The method appears to be more efficient compared to those reported so far for arbitrary shapes. Moreover, feed reactance is built into the analysis. The method presented here can also be used to analyze microstrip antennas with various types of loadings, e.g., shorting pins, matched loads, etc.
IEEE Transactions on Microwave Theory and Techniques, 1997
In this paper, it is shown that Cauchy's method can be used effectively to interpolate/extrapolat... more In this paper, it is shown that Cauchy's method can be used effectively to interpolate/extrapolate narrow-band system responses. The given information can either be theoretical datapoints or measured experimental data over a band. For theoretical data extrapolation or interpolation, the sampled values of the function and, optionally, a few of its derivatives have been used to reconstruct the function. For measured data, only measured values of the parameter are used to create broadband information from limited data as derivative information is too noisy. Cauchy's method assumes that the parameter to be extrapolated/interpolated, as a function of frequency, is a ratio of two polynomials. The problem is to determine the order of the polynomials and the coefficients therein. The method of total least squares (TLS) has been used to solve the resulting matrix equation involving the coefficients of the polynomials. Typical numerical results have been presented to show that reliable interpolation/extrapolation can be done for various system responses.
IEEE Transactions on Microwave Theory and Techniques, 1990
Two techniques are presented for the analysis of electromagnetic radiation and scattering from fi... more Two techniques are presented for the analysis of electromagnetic radiation and scattering from finite microstrip structures. The two techniques are based on two different formulations, viz. the volume-surface and surface-surface formulations. In the volume-surface formulation the finite-sized dielectric is replaced by an equivalent volume polarization current whereas the conducting plates are replaced by equivalent surface currents. For the surface-surface formulation the surface covering the dielectric volume is replaced by equivalent electric and magnetic currents and the conducting plates by surface electric currents. Both techniques can be utilized for the analysis of arbitrarily shaped finite microstrip structures. The techniques are quite accurate, and they are utilized to validate each other. Typical numerical results are presented to demonstrate the agreement between these two solution techniques
IEEE Transactions on Microwave Theory and Techniques, 1997
A new numerical procedure is developed for the solution of the electric field integral equation (... more A new numerical procedure is developed for the solution of the electric field integral equation (EFIE) for arbitraryshaped microstrip structures. This approach is superior over conventional EFIE techniques particularly in the low-frequency region or where the structure to be analyzed is electrically small. A pair of new basis functions is presented which are essential to the solution in the entire frequency range of interest. The new basis functions decompose the surface current density into divergenceless and curl-free parts which essentially get decoupled at the very low end of the frequency spectrum. Typical numerical results are presented for certain examples to illustrate the difference in the results between the two methods.
IEEE Transactions on Antennas and Propagation, 2012
A true domain decomposition method to obtain numerical solution involving electrically large bodi... more A true domain decomposition method to obtain numerical solution involving electrically large bodies using the method of moments (MOM) formulation is the subject matter of the present work. The electrically large body is initially divided into smaller sub-structures. By defining a set of new basis functions adaptively, utilizing the primary basis functions, a solution scheme is developed which completely eliminates the interaction of one substructure with the rest of the body. This procedure enables to solve each substructure independently and involves no iterative solution as a final step. The present method is conceptually simple and applicable to any MOM solution. Further, the method can easily handle multiple right-hand side vectors much the same way as the conventional MOM solution. A few representative numerical examples are presented to illustrate the applicability of the new method.
IEEE Transactions on Antennas and Propagation, 1993
Lengthy comments are offered on some remarks made in the paper by D.A. Vechinski and S.M. Rao (se... more Lengthy comments are offered on some remarks made in the paper by D.A. Vechinski and S.M. Rao (see ibid., vol.40, no.6, p.661-5, June 1992) regarding the solution procedure described by B.P. Rynne (1991). Vechinski and Rao offer arguments in rebuttal
IEEE Transactions on Antennas and Propagation, 2002
In this work, we present the application of specially constructed adapti¨e basis functions to gen... more In this work, we present the application of specially constructed adapti¨e basis functions to generate a diagonal matrix in the method-of-moments solution procedure for the calculation of a scattered electromagnetic field from arbitrarily shaped two-dimensional cylinders excited by a trans¨erse electric incident electromagnetic wa¨e. Se¨eral numerical examples are also presented to¨alidate the new method.
IEEE Transactions on Antennas and Propagation, 2010
We present a new method of moments solution procedure for calculating electromagnetic scattering ... more We present a new method of moments solution procedure for calculating electromagnetic scattering and radiation from conductor/dielectric composite structures. The solution is obtained using triangular patch modeling and a recently developed pair of mutually orthogonal pulse basis functions to represent the equivalent currents J and M. The pulse basis functions are defined with respect to the edges in the triangulated model and partially spread over the triangles connected to the edge. The orthogonality of the basis functions allows the development of stable solutions for all formulations and configurations investigated. A set of numerical results is presented that illustrates the efficacy of the present approach.
IEEE Transactions on Antennas and Propagation, 1991
Page 1. 1034 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 39, NO. 7, JULY 1991 .sin@,P,&am... more Page 1. 1034 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 39, NO. 7, JULY 1991 .sin@,P,'(cose) ~T[P,'(cos8)]2sinBd~ (23) 0 and E,(r,8,4) = 0. Equation (23) expresses the radiation field components at any point outside the spherical body. ...
IEEE Transactions on Antennas and Propagation, 2002
Page 1. IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 50, NO. 12, DECEMBER 2002 1831 Numeri... more Page 1. IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 50, NO. 12, DECEMBER 2002 1831 Numerical Solution of Time Domain Integral Equations for Arbitrarily Shaped Conductor/Dielectric Composite Bodies ...
IEEE Transactions on Antennas and Propagation, 2011
In this work, a new numerical procedure is developed to apply the well-known method of moments (M... more In this work, a new numerical procedure is developed to apply the well-known method of moments (MoM) formulation to electrically large conducting bodies of arbitrary shape. The numerical procedure involves developing a combination of subdomain-entire domain basis functions which result in a sparse moment matrix as opposed to a full matrix in the traditional method. Moreover, the zeros in the MoM matrix are precisely at the same locations where one would have encountered the most significant values. The solution of the new matrix may be obtained using the simple Gauss-Seidel iterative procedure with only two or three iterations. All the traditional advantages of the MoM procedure are retained including the solution for multiple incident fields. Several numerical results are presented to illustrate the validity of the new approach. Index Terms-Fast method, large-body problems, method of moments (MoM), RWG basis.
IEEE Transactions on Antennas and Propagation, 1997
In this paper, we use the matrix pencil approach to extrapolate time-domain responses from three-... more In this paper, we use the matrix pencil approach to extrapolate time-domain responses from three-dimensional (3-D) conducting objects that arise in the numerical solution of electromagnetic field problems. By modeling the time functions as a sum of complex exponentials, we can eliminate some of the instabilities that arise in late times for the electric-field integral equation in the time domain. However, this method can also be utilized for extending the responses obtained using a finitedifference time-domain (FDTD) formulation.
IEEE Microwave and Guided Wave Letters, 1995
In this work, we utilize the finite element technique to open region problems in conjunction with... more In this work, we utilize the finite element technique to open region problems in conjunction with the truncation condition based on the measured equation of invariance (MEI) concept. The major advantage of the present scheme is a significant reduction in the number of unknowns while retaining the sparsity of the generating matrix.~pical numerical results are presented for the solution of Laplace's equation to illustrate the accuracy of the technique.