Electromagnetic field coupling to an electrically small axial dipole antenna in a cylindrical cavity

Abstract

In this paper we present some results of our research of high-frequency electromagnetic coupling to an electrically small axial dipole antenna inside a circular cylindrical cavity. This problem has many practical applications in EMC, e.g., for electronic equipment in aircraft or other aerial vehicles.To solve approximately the corresponding mathematical problem given by an integro-differential equation we used the so called Method of Small Antenna, developed earlier. The calculated input impedance of the antenna in the resonator and the calculated coefficients of the mutual coupling between two antennas are compared to those obtained from a full wave method (MLFMM) and show excellent agreement.

High-Frequency Electromagnetic Field Coupling to Small Antennae in a Rectangular Resonator

“…For simplicity, we assume that the antenna is parallel to the z-axis. The current induced in the antenna satisfies the electric field integral equation (EFIE), which contains the tensor (dyad) Green's function of the cavity [4,5]. The same EFIE equation for the current induced in the excited antenna, can be written in free space.…”

“…The effective electromotive force ε E,eff and the current distribution function f (l) for a passive antenna with a distributed uniform excitation E z (R a L a /C a ), see Figure 2(a) are given by 3and 4, respectively [3][4][5],…”

“…This value is calculated using the resonator Green's function, regularized for coinciding arguments, G E RES , and it depends on both the antenna and resonator parameters. For the passive dipole (distributed excitation), one obtains (detailed derivation and explanation of expression (5) the reader can find in [3,4])…”

“…In the resonator, this Green's function can be calculated by a different way. Here, as in our early research of the small electrical dipole [4], it is convenient to use the resonator Green's function in double sum representation (expansion into transverse waveguide modes of the cavity [7]). It is a diagonal tensor, whose zz-component is (the other components can be obtained by cyclic rearrangement) given by…”

“…In our papers, [4,5], we proposed a method to analyze the coupling to an electrically short dipole (or monopole) antenna in a resonator (Method of Small Antenna, MSA) by consequently using the scattering theory. The MSA is based on the analysis of the integro-differential equation describing the induced current in the neighborhood of the antenna.…”