Scientists at the University of Cambridge in the UK say they have discovered a new way of generating radio waves that could mean aircraft satellite antennas become a lot smaller in future.
The new design of antennas could even be small enough to be integrated into an electronic chip.
Published in the journal “Physical Review Letters”, and reviewed on phys.org, the researchers propose that electromagnetic waves can be generated not only from the acceleration of electrons, but also from a phenomenon known as “symmetry breaking”.
Since Hertz’s earliest experiments in electromagnetic radiation, radio waves have been produced by accelerating electrons along a conductor. This is done by applying an alternating current to the conductor, that changes direction thousands (kHz), millions (MHz) or even thousands of million times a second (GHz).
The bulk of the electromagnetic radiation comes from where the current is at a maximum – that is, where the most electrons are being accelerated.
On receive, the reverse happens – the incoming electromagnetic wave is intercepted by the conductor, which then has a tiny alternating current induced into it. This can then be amplified and turned into a useful signal.
The biggest problem is that the antenna generally has to be of a similar size (usually half) to the wavelength of the radio wave you are trying to generate.
At L-band frequencies (1.6Mhz – such as used in Inmarsat SwiftBroadband) a half-wave antenna is around 9.5cm, so effective antennas tend to be quite large, especially if the antenna has a number of elements phased together.
James Clerk Maxwell
Most of what we know about electromagnetic radiation comes from theories proposed by James Clerk Maxwell in the 19th century. Nothing very revolutionary has been discovered since then.
The new research has looked at breaking the symmetry of the electric field within a conductor, which resulted in radio waves being produced.
The researchers found that by subjecting piezoelectric thin films to an “asymmetric excitation”, the symmetry was broken and electromagnetic radiation was produced.
Piezoelectric materials can be made in thin film forms using materials such as gallium arsenide. Gallium arsenide-based amplifiers and filters are already being used for microwave radar and satellite systems.
In future, we could therefore see antennas built into tiny microchips, with thousands of them then being put together to form a flat panel.
To be honest, this isn’t a million miles away from the work Kymeta is doing on producing its mTenna flat-panel antenna for Inmarsat’s Ka-band GX system. This is still, perhaps, a couple of years away from production.
The mTenna doesn’t use the symmetry-breaking technology, but its overall form factor is similar to what we could see in future.
Other flat-panel Ku-band antennas include Thinkom’s antenna for the Gogo 2Ku system and Panasonic’s low-profile phased-array antenna, both for the commercial airliner market.
The Panasonic antenna has been developed with Boeing Network and Space Systems (N&SS) and offers a broadband, electronically-steered beam, but weighs only 140lb – a 65 percent reduction in operational weight.
What the latest announcement shows is that future satellite antennas are likely to get smaller and flatter, offering less drag and less weight. There still remains the question of their performance at high latitudes though, compared with steerable arrays.