Mutual resistances between horizontal wire antennas near an interface

The problem of radiation of the coupled horizontal wire antennas with a specified current distribution, located near to a planar interface between two media is considered. Expressions for evaluation of a mutual impedance, mutual radiation resistance and mutual resistance of losses between dipoles above the ground are obtained. The results of numerical evaluations of the mutual resistances between two half-wave dipoles as functions against a distance between them are presented in graphical form

Radiation efficiency of coupled vertical dipole antennas located above a lossy half-space

The study of properties of an antenna placed over a lossy half-space occupies an important place in the antenna theory. However, despite the long list of publications on the subject, the influence of the ground parameters on the antenna element interaction coupling and the antenna arrays efficiency have not been adequately investigated. In this paper, a rigorous impedance approach to analysis radiation efficiency of the coupled dipole antennas, placed near the air-ground interface, is developed

Antenna Analytical Representation by a Two-Port Network

System analysis is a powerful tool for researching modern wireless systems. This includes breaking such systems into parts that make them up and studying how these parts work together. All these parts can be represented as “black boxes” in the form of two-port or multiport networks with the common system of parameters. Antenna is an integral part of any wireless system, so it should be also represented as a two-port network. In this paper, an analytical model of an arbitrary single antenna in the form of a two-port network, whose electrical and noise parameters are described in terms of scattering matrices, is obtained. The initial data for creating the model are the antenna fundamental parameters, viz., the input reflection coefficient and the radiation efficiency. Applications of this model for antenna analysis operating in the transmitting, receiving, and scattering modes are demonstrated. A numerical example using the antenna scattering matrix for computer simulation of a wireless connection is given

Modeling dipole antenna arrays placed, near to interface between two media

A modeling technique of antenna arrays made from horizontal wire dipoles located over an interface of two media is developed. It is based on the moment method for wire antennas. The emphasis is placed on evaluating matrix parameters of radiation system and using them for analysis of power characteristics of ground based antenna arrays, especially of their efficiency dependence from the input currents distribution. Numerical analysis results are given for the radiation efficiency of the phased antenna array, located near the ground surface, at beam scanning in the elevation plane

An Active Ribbon Dipole as an Array Element Prototype for the Lunar Very Low Frequency Radio Telescope

This work is concerned with a detailed study of an active antenna, which can serve as a prototype of a phased array antenna element for a future lunar very-low-frequency (VLF) radio telescope operating in the frequency range of 1–30 MHz. The antenna consisted of a ribbon symmetrical dipole and a low-noise preamplifier. A dipole 10 m long lay on a flat surface of lunar soil, consisting of a layer of regolith 10 m thick and solid bedrock. The dipole parameters were determined by full-wave simulation using the Altair Feko 2022 software. The preamplifier was a single-stage HEMT low-noise amplifier, whose parameters were determined using the Advanced Design System 2023 software. An active antenna was analyzed using a model created to calculate all electrical and noise parameters. Special attention was paid to the analysis of the antenna sensitivity in terms of the System Equivalent Flux Density (SEFD) and Sky Noise Dominance (SND), taking into account changes in the lunar ambient temperature from 100 K to 400 K. It was shown that the frequency dependences of many active antenna parameters, in particular, radiation efficiency, directivity, effective area, SND, and SEFD had noticeable oscillatory components. The radiation pattern of the antenna was also subject to cyclical changes that occur in sync with the changes in directivity. These properties of the active antenna, caused by the presence of two-layer soil, should be considered when developing future lunar VLF radio telescopes

Maximization of the power parameters of antenna arrays with suppression of the cross-polar radiation

Polarization isolation of antennas is among the widely used methods for providing electromagnetic compatibility of various radio and electronic facilities. However, it turns out to be efficient in the only case when the cross-polar radiation of the antennas has sufficiently low level. Suggested in this paper is a method for optimizing the current distribution in an antenna array to provide its high performance along with suppression of the power radiated by cross-polar waves

Effect of the ground screen on sensitivity of low-frequency radio telescope array element

The Giant Ukrainian Radio Telescope (GURT) is a new generation radio telescope with active phased antenna array intended to operate within 10–80 MHz range. The radio telescope is being constructed now in Ukraine. The array elements are active antennas in form of flat wire dipoles integrated with low-noise preamplifiers. In the paper we present a comparative analysis of two GURT array element versions that differ in presence or absence of wire grid ground screen under the dipole. The analysis results are given and discussed