Abstract
We report a method to obtain the wave number and input impedance of a very low frequency (VLF) insulated linear antenna in an anisotropic ionosphere. Due to the anisotropy, electromagnetic fields in the ionosphere are decomposed into the ordinary wave and extraordinary wave. Wave equations for the layered structure are applied to access the wave number of the insulated antenna in the ionosphere via the derivation of the eigenvalue equation by using boundary conditions. The expression for the wave number is given based on some approximation formulas. Then, King’s antenna theory is further employed to solve the input impedance and current distribution of the antenna in the anisotropic medium. After the validation of the method is performed, near-field characteristics for an insulated antenna with different medium parameters in the anisotropic ionosphere are discussed. Effects of the electric density and geomagnetic field of the time-and space-varying anisotropic ionosphere on the distribution of normalized current are analyzed. This finding provides a promising avenue for getting electromagnetic characteristics of space-borne antennas.
Highlights
International Journal of Antennas and PropagationEither the anisotropy was not considered or influences of the insulation layer were neglected in these studies [21]
Near-field characteristics of an insulated linear antenna in an anisotropic ionosphere are studied. e electromagnetic waves, which are expressed in the combination of the ordinary wave (O-wave) and extraordinary wave (E-wave), in the anisotropic ionosphere are given. e eigenvalue equation containing the wave number of the layered antenna structure is derived by using boundary conditions. en, King’s antenna theory is applied to get the input impedance and current distribution of the insulated antenna after the approximate formula for the wave number is obtained. e effects of medium parameters of the insulated antenna and anisotropic ionosphere on the wave number, input impedance, and current distribution of the insulated linear antenna in the ionosphere are investigated
E real part of relative permittivity, conductivity, and wave vector for the conductor are εI, σI, and kI ω [με0] 1/2 ≈1/2 and for the insulation layer are εII, σII, and kII ω [με0]1/2, respectively. e medium in the IIIrd region is the anisotropic ionosphere. e length of the antenna is 2l. e antenna is parallel to the geomagnetic field with the amplitude B0. e antenna is driven by applying feeding voltage V0, which denotes the Dirac function δ (z) at its center across a thin gap to generate electromagnetic fields
Summary
Either the anisotropy was not considered or influences of the insulation layer were neglected in these studies [21]. Analytical and numerical methods used to simulate the wave number and input impedance of a VLF insulated linear antenna in the anisotropic ionosphere are desirable. En, King’s antenna theory is applied to get the input impedance and current distribution of the insulated antenna after the approximate formula for the wave number is obtained. E effects of medium parameters of the insulated antenna and anisotropic ionosphere on the wave number, input impedance, and current distribution of the insulated linear antenna in the ionosphere are investigated. Where kl and Zc are the wave number in (34) and characteristic impedance of the insulated antenna in the anisotropic ionosphere, respectively.
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