Free-space Dyadic Green's Function Research Articles

The free-space dyadic Green function is orthogonal to its curl

The free-space dyadic Green function in electromagnetics is orthogonal to its own curl on any spherical surface whose center is the source point.

Improved Prediction of the Wideband Beam Pattern Shape of Antenna Array Based on Infinitesimal Dipole Modeling

An improved prediction of the wideband beam patterns of an antenna array is proposed based on the active element pattern method and infinitesimal dipole (ID) modeling. In the conventional method, the gain of an antenna array can be easily analyzed. However, the prediction of the shape of the beam pattern is limited due to the usage of the slow-varying assumption and the scaling factor. On the contrary, the proposed method uses the free-space dyadic Green's function, which varies for frequencies and all ID elements. By eliminating the slow-varying assumption and the scaling factor, the proposed method, predicting the shape of the beam pattern of an antenna array, is more accurate than the conventional method. The proposed method was verified by the wideband beam synthesis problem for a seven-patch antenna array.

Time Domain Coupled Field Dyadic Green Function Solution for Maxwell's Equations

The free space time domain coupled electric and magnetic field integral equation solution for Maxwell's differential equations is derived. The coupled field integral equation solution is expressed as a vector containing the electric and magnetic fields found in terms of a surface integral over the equivalent surface currents on a boundary, an integral over the electric and magnetic current sources in the region enclosed by the boundary, and a volume integral over the initial field in the bounded region. Because of the irreversibility of the vector differential equation and the lack of spatial symmetry in the corresponding free space dyadic Green function, as a starting point the Green differential equation is replaced by the reciprocal (adjoint) equation and the dyadic Green function is replaced by its transpose. These replacements plus identities that relate the components of the Green function to its transpose lead in a straightforward way to the coupled field solution. The general dyadic expression derived here provides a framework for developing source current, boundary integral, and propagator methods that are based on the interaction between the electric and magnetic vector field components in the time domain.

Spherical Wave Expansion of the Time-Domain Free-Space Dyadic Green's Function

The importance of expanding Green's functions, particularly free-space Green's functions in terms of orthogonal wave functions is practically self-evident when frequency domain scattering problems are of interest. With the relatively recent and widespread interest in time-domain scattering problems, similar expansions of Green's functions are expected to be useful in the time-domain. In this paper, an expression, expanded in terms of orthogonal spherical vector wave functions, for the time-domain free-space dyadic Green's function is presented and scattering by a perfectly conducting sphere is studied as an application to check numerically the validity and to demonstrate the utility of this expression.

Analysis of aperture coupling of electromagnetic energy in cylindrical wall [EMC applications

The coupling of electromagnetic (EM) waves through an aperture in a cylindrical wall is analyzed by the method of moments (MoM), in conjunction with the free-space dyadic Green function. A transmission coefficient of the aperture is defined and calculated. The result provides useful physical insight in electromagnetic compatibility (EMC) issues of sophisticated electronic systems.

Some remarks on antenna response in a reverberation chamber

The simple formula, =(E/sub 0//sup 2///spl eta/)(/spl lambda//sup 2//8/spl pi/), for the received power of an antenna with a matched load in an over-moded cavity actually holds for an antenna of any shape and size. This can be seen from the close connection between the correlation tensor of the cavity field at two different points and the imaginary part of the free-space dyadic Green's function.

Evanescent plane waves and the far field: Resolution of a controversy

We show that the evanescent part of the plane wave representation of the free-space dyadic Green function contributes to the far field only along a distinguished axis. The claim of contribution of evanescence in all directions is incorrect as it arises from a flawed procedure, but a limited version of that claim may have merit.

A Note on the Integral Equations for the Scattering of a Plane Wave by an Electromagnetically Permeable Body

ABSTRACT The integral equations governing the scattering of a plane wave by an electrically and magnetically permeable obdy are investigated by two alternative methods. In the first method, the homogeneous wave equations for Ē are integrated with the aid of the free-space dyadic Green's function that yields directly an integral equation for Ē. In the second method the equivalent polarized currents are introduced as previously done by Harrington that yields two coupled integral equations for Ē and . By eliminating between these two equations one obtains the same integral equation for Ē as derived by the first method.