Anisotropic Microwave/Terahertz Metamaterials for Satellite Applications (ANISAT)

Lead Research Organisation: Loughborough University
Department Name: Wolfson Sch of Mech, Elec & Manufac Eng

Abstract

There is growing interest in the UK space sector for communications, imaging and earth observation. Key to this is sending and receiving electromagnetic waves. To enable higher communication rates and get greater accuracy in imaging often higher frequencies are used. This project will develop new structures using microfabrication techniques to develop novel antennas and polarizers for satellites and the earth segment over frequencies from 28 GHz up to 1 THz. This frequency range overlaps and extends the currently used frequencies.

ANISAT will address these five technical challenges:

1) Designing anisotropic metamaterials;
2) Exploiting these properties to design novel antennas, polarizers and RF devices;
3) Developing novel methods of measuring these properties;
4) Microfabricating heterogeneous anisotropic structures;
5) Combining these elements into a series of demonstrators.

The above five points are addressed in more detail below:

i) When an electromagnetic wave moves through a material it is slowed down by the dielectric properties. If an artificial dielectric can be composed of small (compared to a wavelength) rectangular or elliptical inclusions, then this composite material will behave differently when the incident electromagnetic wave has different polarizations. This can be exploited to create circularly polarized antennas where the electric field traces a circle in time. This is an advantageous property for space communications.

ii) Currently, dielectric measurements only consider the dielectric properties for one polarization and effectively assume the materials are isotropic. ANISAT will develop a novel measurement system using resonant metasurfaces that can measure the properties along all three axes. This will open a new degree of freedom for antenna and radiofrequency engineers.

iii) These anisotropic artificial dielectrics will be used to design novel circularly polarized antennas. It is currently challenging to feed antennas to create circular polarization at frequencies above 50 GHz due to the small scale of the feed structure. High gain multi beam cavity antennas and polarizers will be designed at a range of frequencies up to 1 THz.

iv) Initial anisotropic artificial dielectrics will be fabricated using 3D-printing. This provides a simple and readily exploitable fabrication process. However, the upper frequency range is limited to approximately 40 GHz by the size of the small-scale air/metal inclusions inside the composite. Above this frequency the inclusions approach the scale of a wavelength and they become resonant. To extend the frequency range, novel microfabrication processes in clean rooms will be developed and exploited. These include fully metallised SU8 photoresist polymers and/or silicon layers with a high dimensional accuracy of the scale of a few microns.

v) The learning process will be multidisciplinary and iterative as each stage innovates further advances. The close geographical proximity of the two universities will be highly beneficial in this regard. The plan is to create laboratory demonstrators that can be showcased to industry. These provisionally include: a novel dielectric measurement system; a high gain circularly polarized antenna at Ka band (26 - 40 GHz); a circularly polarized Fabry-Perot antennas at frequencies up to 110 GHz; and linear to circular polarizers and beam splitters from 220 - 300 GHz and at a central frequency of 640 GHz.

Planned Impact

Satellites are/will be used for the following applications: Worldwide internet and the Internet of Things; Phone and secure communications; Satellite television; Measuring air pollution; Monitoring ozone, nitrogen dioxide and methane levels; Space exploration; Accurate mapping of the magnetosphere; Supplying information about major disasters such as hurricanes and earthquakes and emergency communications; Automatic identification system (AIS) and automatic dependent surveillance broadcast (ADS-B) tracking systems used by ships and planes.

All these technologies are reliant on electromagnetic waves. ANISAT will develop novel anisotropic metamaterials for circularly polarized antennas and small lightweight polarizers. By moving to higher frequencies, more functionality and higher data rates are made possible.

This project is timely due to the emergence of smaller, lighter and hence cheaper CubeSats and SmallSats. 1200 SmallSats were launched over the past decade. This will grow to 7000 Smallsats over 2018-2027 which is valued at £30B for satellite manufacturing and launch. The world market for satellites is expected to have an annual compound rate of growth of 6.8% over the next decade. The global market for satellite antennas is predicted to grow to ~£2.5B by 2023.

Economic benefit: The UK is a world leader in the design, manufacture and operation of communications satellites. 25% of world's satellites are made in the UK. The UK Space economy is worth ~ £12B with 37,000 directly employed workers and 72,000 indirect jobs. The Government's target is to grow this to £40B. In November 2017, the UK Government's Industrial Strategy identified Grand Challenges to put the UK at the forefront of the industries of the future: Data-Driven Economy and Future Mobility. Underpinning both is demand for novel high speed, reliable communication.

Environmental benefit: By accurately monitoring the ozone layers, the effects of climate change can be better understood. In addition, a recent European Space Agency study estimated that the potential cost to Europe from a single extreme space weather event could be as high as £15B. Much of this disruption could be avoided through accurate forecasting.

The academic team will benefit from working on a multidisciplinary project that pushes the envelope in terms of scale and frequency range. The ANISAT project will enhance the knowledge base of industry through collaboration with eleven Project Partners from key sectors helping to position the UK as a leading centre of excellence and innovation in this emerging field, creating jobs and sales ultimately benefiting UK Plc. The Project Partners will be able ensure that the research is aligned with industrial applications from the outset. These companies have existing and future interest in satellite antennas, sensing systems as well as 5G communications. Future systems will be enhanced by developing new artificial materials using state-of-the-art microfabrication techniques. This will lead to new antenna and metamaterial designs. The project will also develop new methods for measuring the dielectric properties in all three axes which is valuable to industry as it accelerates the design to manufacture timeline. By disseminating the work, additional Project Partners will be encouraged to join the Team throughout the project. Two Project Partners have been specifically chosen to ensure dissemination to the wider public.

This grant will contribute significantly to the following EPSRC Key areas: Manufacturing the Future; Digital Economy: Information Systems; Pervasive and Ubiquitous Computing. With the potential to enable new materials; innovative solutions and modelling capability, it resonates strongly with the Productive Nation. By augmenting diagnostic and imaging systems it feeds into the development of technologies which will impact on Healthy Nation and enhanced communication systems will contribute to Resilient Nation.

Publications

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Al-Nuaimi M (2020) Aperiodic Sunflower-Like Metasurface for Diffusive Scattering and RCS Reduction in IEEE Antennas and Wireless Propagation Letters