Tiny antennas that would fit on computer chips will be possible thanks to a major breakthrough in electromagnetism technology, say University of Cambridge scientists in what they describe as the “last frontier of semiconductor design.”
The Cambridge research team, led by Professor Gehan Amaratunga, says its new insight into electromagnetism could help identify the points where the theories of both classical electromagnetism and quantum mechanics merge.
Prof. Amaratunga and colleagues believe they have cracked one of the enigmas of electromagnetism, which they claim will make it possible to create microscopic antennas so tiny that can be fitted into micro-electronic chips.
The radiation pattern from a dipole antenna showing symmetry breaking of the electric field. (Image: University of Cambridge)
A huge leap for wireless communications
These super-small antennas would represent a major milestone for wireless communications, the researchers wrote in the journal Physical Review Letters.
The authors explained that electromagnetic waves are generated not only from the acceleration of electrons, but also from symmetry breaking.
Electron acceleration caused by radiation is a phenomenon that was first identified more than one century ago. It has no equivalent, that current scientists know of, in quantum mechanics, where they say electrons jump from higher to lower energy states.
The authors said their new observations of radiation resulting from broken symmetry of the electric field may reveal some associations between the two fields.
Antennas are places in communications towers and mobile devices to launch energy into free space in the form of electromagnetic or radio waves, and to collect energy from free space to feed data into devices.
Modern electronics has been constrained by a major challenge – antenna size. They are still bulky and incompatible with electronic circuits, which are getting smaller and smaller all the time.
Antennas, the major obstacle in micro-electronics
“Antennas, or aerials, are one of the limiting factors when trying to make smaller and smaller systems, since below a certain size, the losses become too great.”
“An aerial’s size is determined by the wavelength associated with the transmission frequency of the application, and in most cases it’s a matter of finding a compromise between aerial size and the characteristics required for that application.”
Researchers say there is another problem with aerials – they don’t know much about the physical variables related to energy radiation. For example, there is currently no well-defined mathematical model to the operation of available practical aerials.
Not much progress since Clerk Maxwell’s theories
Scottish scientist James Clerk Maxwell (1831-1879) was the first to propose theories regarding electromagnetic radiation, which state that it is generated by accelerating electrons. Since then, we have not made much progress in our knowledge of electromagnetic radiation.
Maxwell’s theory becomes problematic when dealing with radio wave emission from a dielectric solid, a material which usually acts as an insulator, where electrons are not free to move around. Even so, dielectric resonators are currently used as mobile phone antennas.
Dr. Dhiraj Sinha, lead author, said:
“In dielectric aerials, the medium has high permittivity, meaning that the velocity of the radio wave decreases as it enters the medium.”
“What hasn’t been known is how the dielectric medium results in emission of electromagnetic waves. This mystery has puzzled scientists and engineers for more than 60 years.”
The Cambridge science team, working alongside the National Physical Laboratory and Cambridge-based dielectric antenna company Antenova Ltd., used thin films of piezoelectric materials, an insulator which is deformed or vibrated when voltage is applied.
At a specific frequency, the researchers found that these materials become both efficient resonators and radiators, which means they can be used as aerials.
The authors believe that this phenomenon occurs due to symmetry breaking of the electric field associated with electron acceleration.
Physicists say symmetry is an indication of a constant feature of a specific aspect in a given system. When electronic charges are still, there is symmetry in the electric field.
Dr. Sinha commented:
“In aerials, the symmetry of the electric field is broken ‘explicitly’ which leads to a pattern of electric field lines radiating out from a transmitter, such as a two wire system in which the parallel geometry is ‘broken’.”
Dr. Sinha and colleagues found that when the thin piezoelectric films were subjected to an asymmetric excitation, the symmetry of the system was correspondingly broken, resulting in a symmetry breaking of the electric field, and the generation of electromagnetic radiation.
As Mr. Maxwell had predicted more than one hundred years ago, the electromagnetic radiation emitted from the dielectric materials is caused by accelerating electrons on the metallic electrodes attached to them, and the explicit symmetry breaking of the electric field.
Breaking the symmetry and having accelerating electrons
Prof. Amaratunga said:
“If you want to use these materials to transmit energy, you have to break the symmetry as well as have accelerating electrons – this is the missing piece of the puzzle of electromagnetic theory.”
“I’m not suggesting we’ve come up with some grand unified theory, but these results will aid understanding of how electromagnetism and quantum mechanics cross over and join up. It opens up a whole set of possibilities to explore.”
This new discovery will help push forward technology in two fields:
– Mobile Technology, and
– The Internet of Things: where nearly everything in our homes and offices, including thermostats, fridges, TVs, toasters, alarm systems, lighting systems, etc. will be linked up to the Internet.
Billions of devices will be needed to hook them all up, and being able to place a tiny aerial into an electronic chip would be a giant technological leap.
Piezoelectric materials can be produced in thin film forms using lithium niobate, gallium nitride and gallium arsenide.
Amplifiers and filters based on gallium arsenide are already on the market. This new breakthrough opens up novel ways of fitting antennas onto chips as well as other components.
Dr. Sinha said:
“It’s actually a very simple thing, when you boil it down. We’ve achieved a real application breakthrough, having gained an understanding of how these devices work.”
The research was financed by the East of England Development Agency, Cambridge University Entrepreneurs, Cambridge Angels, the Nokia Research Centre, and the Cambridge Commonwealth Trust and the Wingate Foundation.
Citation: Dhiraj Sinha and Gehan A. J. Amaratunga. “Electromagnetic radiation under explicit symmetry breaking.” Physical Review Letters 114, 147701 (2015).