Invention and development of the Yagi-Uda antenna, and the self-complementary antenna are described. Analysis methods of large loop antennas and the improved circuit theory (ICT) for design of linear antennas are presented. Recent developments of axial mode helical antennas and spiral antennas for radiating circularly polarized waves are also described.

An alternative polynomial expansion for electromagnetic field estimation inside three-dimensional dielectric scatterers is presented in this article. In a continuation with the previous work of authors, the Tensor-Volume Integral Equation (TVIE) is solved by using the Galerkin-based moment method (MoM) consisting of a combination of entire-domain and sub-domain basis functions including three-dimensional polynomials. Instead of using trivial power polynomials, Legendre polynomials are adopted for electromagnetic fields expansion in this study. They have the advantage of being a set of orthogonal functions, which allows the use of high-order basis functions without introducing an ill-condition MoM matrix. The accuracy of such approach in MoM is verified by comparing its numerical results with that of exact analytical method such as Mie theory and conventional procedures in MoM. Besides, it is also confirmed that the condition number of the MoM matrix obtained with the proposed approach is lower than that of the previous approaches.

This paper includes different approaches for analysis of a thin-wire antenna in the presence of de-ionized water box at different temperatures as a high-permittivity three-dimensional dielectric body. In continuation with the previous work of authors, first, the coupled tensor-volume/line integral equations is solved by using Galerkin-based moment method (MoM) consisting of a combination of entire-domain and sub-domain basis functions including three-dimensional polynomials with different degrees. Then, the accuracy of such MoM, specifically for a high-permittivity dielectric scatterer, is substantiated by comparing its numerical results with that of FDTD method and some experimental data.

This paper presents method that offers the fast and accurate analysis of large-scale periodic array antennas by conjugate-gradient fast Fourier transform (CG-FFT) combined with an equivalent sub-array preconditioner. Method of moments (MoM) is used to discretize the electric field integral equation (EFIE) and form the impedance matrix equation. By properly dividing a large array into equivalent sub-blocks level by level, the impedance matrix becomes a structure of Three-level Block Toeplitz Matrices. The Three-level Block Toeplitz Matrices are further transformed to Circulant Matrix, whose multiplication with a vector can be rapidly implemented by one-dimension (1-D) fast Fourier transform (FFT). Thus, the conjugate-gradient fast Fourier transform (CG-FFT) is successfully applied to the analysis of a large-scale periodic dipole array by speeding up the matrix-vector multiplication in the iterative solver. Furthermore, an equivalent sub-array preconditioner is proposed to combine with the CG-FFT analysis to reduce iterative steps and the whole CPU-time of the iteration. Some numerical results are given to illustrate the high efficiency and accuracy of the present method.

The conjugate gradient-fast multipole method (CG-FMM) is one of the powerful methods for analysis of large-scale electromagnetic problems. It is also known that CPU time and computer memory can be reduced by CG-FMM but such computational cost of CG-FMM depends on shape and electrical properties of an analysis model. In this paper, relation between the number of multipoles and number of segments in each group is derived from dimension of segment arrangement in four typical wiregrid models. Based on the relation and numerical results for these typical models, the CPU time per iteration and computer memory are quantitatively discussed. In addition, the number of iteration steps, which is related to condition number of impedance matrix and analysis model, is also considered from a physical point of view.

A new approach for solution of the Tensor-Volume Integral Equation (TVIE) using Galerkin-based moment method (MoM) for three-dimensional dielectric bodies is proposed. Two problems of plane wave scattering by a dielectric sphere and a thin-wire antenna in close proximity to a dielectric body are investigated. In both cases, cubic modeling is applied and a combination of entire-domain and sub-domain basis functions, including three-dimensional polynomial functions with different degrees is utilized for field expansion inside dielectric bodies. Power polynomial is adopted for this purpose and its property is discussed over the proposed mixed-domain MoM formulation. Numerical examples show that based on the proposed method, a relative fast algorithm and suitable accuracy are achieved compared with conventional MoM. The accuracy of the proposed method is verified by comparing it with the Mie theory, conventional MoM and the FDTD method.

An integral equation approach with a new solution procedure using moment method (MoM) is applied for the computation of coupled currents on the surface of a printed dipole antenna and inside its high-permittivity three-dimensional dielectric substrate. The main purpose of this study is to validate the accuracy and reliability of the previously proposed MoM procedure by authors for the solution of a coupled volume-surface integral equations system. In continuation of the recent works of authors, a mixed-domain MoM expansion using Legendre polynomial basis function and cubic geometric modeling are adopted to solve the tensor-volume integral equation. In mixed-domain MoM, a combination of entire-domain and sub-domain basis functions, including three-dimensional Legnedre polynomial basis functions with different degrees is utilized for field expansion inside dielectric substrate. In addition, the conventional Rao-Wilton-Glisson (RWG) basis function is employed for electric current expansion over the printed structure. The accuracy of the proposed approach is verified through a comparison with the MoM solutions based on the spectral domain Green's function for infinitely large substrate and the results of FDTD method.

A method using the microstrip line resonator is applied to measurements of the dielectric properties of a substrate and the surface resistance of a conducting strip line versus the frequency as well as the temperature. The variational expressions for the capacitance per unit length of several microstrip lines such as an inverted microstrip line and multi-layer microstrip lines are derived. The expression involves an integral along a semi-infinite interval, but the numerical integration is very easy. Effects of a buffer layer deposited on the substrate are investigated by using a multi-layer microstrip line model. The permittivity and the loss tangent of several dielectric materials are measured by the MSL and the IMSL or the multi-layer microstrip resonator. The measured surface resistance of copper and iron is also presented to show the validity of the present method. The surface resistance of a BSCCO thick film is also presented.

A numerical hybrid method for analyzing the wireless channel of Multiple-Input Multiple-Output (MIMO) communication system is proposed by combining of the method of moments (MoM) and the finite difference time domain (FDTD) method. The proposed method is capable of investigating a more practical MIMO wireless channel than the conventional methods, and CPU time is much less than that of the FDTD method in analysis of spatial statistical characteristics of received signals. Based on the channel transfer matrix obtained by the proposed method, the wall effect on indoor MIMO channel capacity are investigated with consideration of received power, Ricean K-factor and effective degrees of freedom (EDOF) of multipaths by changing the wall locations and material.

Convergence of the iterative method based on the successive overrelaxation (SOR) method is investigated to solve the matrix equation in the moment analysis of array antennas. It is found this method can be applied to the sub domain method of moments with fast convergence if the grouping technique is applied and the over-relaxation parameter is properly selected, and the computation time for solving the matrix equation can be reduced to be almost proportional to the second power of the number of unknowns.

An estimation method of source location of undesired electromagnetic wave from electronic devices by using the MUSIC algorithm is proposed. The MUSIC algorithm can estimate the direction of arrival accurately, however, the estimation error is large in the case of short range multiple coherent sources. In order to overcome this problem, a method to improve the estimation accuracy is presented. Experimental results show that the proposed method can reduce the maximum estimation error from 7 cm of the conventional method to 2 cm.

On the huge-scale array antenna for SSPS (space solar power systems), the problem of faulty elements and effect of mutual coupling between array elements should be considered in practice. In this paper, the effect of faulty elements as well as mutual coupling on the performance of the huge-scale array antenna are analyzed by using the proposed IEM/LAC. The result shows that effect of faulty elements and mutual coupling on the actual gain of the huge-scale array antenna are significant.

The relation between the radiation pattern and the dimension of the conducting box for a portable telephone is illustrated both theoretically and experimentally. The Galerkin-moment method using the Fourier series expansion for the surface current of the conducting box, which has a great advantage of having a high accuracy, is employed to obtain the radiation pattern. As an example of antennas, a quarter-wavelength monopole antenna having a sinusoidal current distribution is used. As a result, it is pointed out that the radiation pattern of a monopole antenna mounted on the box tends to tilt in a lower direction both in theory and in experiment as well. The relation between the radiation pattern and the location of the monopole antenna is also described. An asymmetrical, or distorted pattern is observed when the monopole antenna moves away from the center of the top plane.

In order to improve the detection performance in passive millimeter-wave (PMMW) imaging, a new method forwarding a null in the direction of human body and objects is proposed. The forward-nulling PMMW imaging using a dielectric tube occupied by cooling water placed near the focus line of a parabolic cylinder are performed. It is shown experimentally that the contrast between human body and conducting objects such as a conducting plate and a conducting sphere is improved by the presence of the cooling dielectric tube and parabolic cylinder.

A new method is proposed in this paper for reducing the MF broadcast wave induction field on overhead power transmission lines during maintenance and inspection work of the line. Power transmission usually has to be stopped in the circuit being worked on, and the conductors are grounded to the steel towers at both ends of the worked section of the line to prevent electric shocks that may be caused by the commercial frequency induction field induced by the current running through the transmission circuit. In these situations, a very strong RF induction field is sometimes observed in the circuit undergoing maintenance work when a high power MF broadcast antenna is located near the transmission line. It has been found that this strong RF induction is caused by the resonance of one or two wavelengths in the closed loop circuit consisting of the conductors and the steel towers (including the ground), and that the strong induction due to the MF field can be avoided by inserting induction coils of appropriate values between the conductors and the steel towers. In this paper, a simple alternative method for reducing the MF induction field by carefully selecting appropriate towers for the grounding is proposed. In this method, the two towers to be grounded are chosen from among the four towers adjacent to the towers that are being worked on. By selecting the correct two towers to be grounded we can ensure that the resonance frequency does not correspond with the frequency of the broadcast wave, and we demonstrate that the RF induction field can be considerably reduced.

A new iterative algorithm based on the Gauss-Seidel iteration method is proposed to solve the matrix equation in the MoM analysis of the array antennas. In the new algorithm, the impedance matrix is decomposed into a number of sub matrices, which describe the self and mutual impedance between the groups of the array, and each sub matrix is regarded as a basic iteration unit rather than the matrix element in the ordinary Gauss-Seidel iteration method. It is found that the convergence condition of the ordinary Gauss-Seidel iteration scheme is very strict for the practical use, while the convergence characteristics of the present algorithm are greatly improved. The new algorithm can be applied to the sub domain MoM with a fast convergence if the grouping technique is properly used. The computation time for solving the matrix equation is reduced to be almost proportional to the square of the number of the array elements. The present method is effective in MoM analysis of solving large-scale array antennas.

A new source model for MoM analysis by using sinusoidal reaction matching technique is proposed for linear antenna analysis. This source model assumes a constant feeding gap and uniform electric field distribution inside the gap. The analysis results are compared with the results of the conventional models and measurement. It is found that the new model can incorporate the effect of the length of driving gap and is more accurate and more stable than that from the conventional source models. The proposed source model is simple and easy to use. This source model, together with the full kernel formulation, makes it possible to analyze the linear dipole antennas with no limitation of ratio of segment length to radius.