Research Associate, Macquarie University
To develop ground terminal antennas for providing high-quality internet via LEO satellites.
It is estimated that more than half of the world population, that about 4.2 billion people, do not have regular access to the internet. In the least developed countries, only one out of every ten people is online. Poor internet connectivity (insufficient speed or no connection at all) is a problem in remote regional areas of even the developed countries like US, Australia, and Canada. To address this global “digital divide” and to cater for future bandwidth demands, satellite internet is considered as a most feasible and optimal solution. This solution relies on a large number (hundreds) of low cost low earth orbit (LEO), i.e. non-geosynchronous, satellites. An essential part of the solution is a low-cost and high-performance steerable beam antenna for a ground terminal. Beam-steering is, therefore, imperative to realize global connectivity using futuristic satellite internet services. The current beam-steering antenna techniques can be broadly grouped into two types. The first type is to design a large antenna with a fixed beam and move the whole antenna to steer its beam in two angular dimensions. The second method is to design a two-dimensional antenna array with several hundreds or thousands of low-gain antennas, and steer its beam electronically using a large number of electronic devices. Both of the existing beam steering techniques cannot be a solution for realizing ‘global connectivity’ because they are either too bulky or too expensive. We have developed an innovative third method of beam steering, to fill the large gap between the two current methods mentioned above. Our method preserve the advantages of current mechanical methods (high efficiency and high power handling) without the limitation of bulkiness. At the same time this method is better than electronically-steered arrays because it is extremely efficient and does not suffer from issues associated with electronic devices such as non-linearity, distortion, heating and poor power handling. Our high-performance, low-profile steerable antenna concept has a planar base antenna and two specially designed metasurfaces. The metasurfaces are placed very close, within a fraction of a wavelength, to the antenna in its near field. Each of the metasurfaces comprises of spatially distributed phase shifting cells. With two independently rotating metasurfaces, antenna beam can be directed to any direction within a large cone.
Abstract: In this paper, theoretical and numerical studies of perfect/nearly-perfect conversion of a plane wave into a surface wave are presented. The problem of determining the electromagnetic properties of an inhomogeneous lossless boundary which would fully transform an incident plane wave into a surface wave propagating along the boundary is considered. An approximate field solution which produces a slowly growing surface wave and satisfies the energy conservation law is discussed and numerically demonstrated. The results of the study are of great importance for the future development of such devices as perfect leaky-wave antennas and can potentially lead to many novel applications.
Pub.: 22 Jun '17, Pinned: 28 Aug '17
Abstract: Extraordinary transmission through a small aperture is of great interest. However, it faces a limitation that most of approaches can not realize the tunable transmission property, which is not benefit for the miniaturization of the microwave system. Here, we demonstrate a magnetically tunable broadband transmission through a small aperture. By placing two ferrite rods symmetrically on both sides of a single small aperture, the strongly localized electromagnetic fields are effectively coupled to the two ferrite rods. Both the simulated and experimental results indicate that such structure not only realizes a nearly total transmission through a small aperture, but also obtains a magnetically tunable property. This work offers new opportunities for the miniaturization of the microwave system.
Pub.: 23 Jul '15, Pinned: 28 Aug '17
Abstract: The simulation and experimental studies of a probe-fed dual segment cylindrical dielectric resonator antenna with metamaterial superstrate are presented in this paper. The antenna consists of a ceramic material (SrLa2Mg2W2O12) of dielectric constant εr = 22 and loss tangent tan δ = 0.0021 acting as upper segment and commercially available Teflon having dielectric constant of 2.1 acting as lower segment. The infinity-shaped metamaterial has been used as superstrate. The simulation study has been carried out using Ansys’s high frequency structure simulator (HFSS) software. The variation of reflection coefficient with frequency, radiation pattern, and gain of the antenna with and without metamaterial superstrate were simulated and measured in X-band. The antenna bandwidth is increased by 94 % through simulation and 52 % experimentally with the use of metamaterial as a superstrate. The directive radiation pattern with narrow beamwidth is obtained with the use of metamaterial. The use of metamaterial superstrate enhances the peak gain of the antenna by 105 % through simulation and 103 % experimentally.
Pub.: 16 May '15, Pinned: 28 Aug '17
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