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EDNE MAY 2015

pulse Antenna-on-a-chip may be feasible, EM research indicates You may have thought that after more than a century of radio communications, the physics of antenna operation would be entirely understood: apparently not, according to a group of researchers at the University of Cambridge. Their work deals with the mechanisms that launch energy into free space (in transmission) and, reciprocally, capture it from the electromagnetic fields in reception. One of the consequences of their work is that it appears possible that effective antennae might be fabricated at physical scales comparable to those of integrated circuit dice. That would open up the possibility of a completely chip-scale system, including all elements of RF communication – which would be an enticing prospect for construction of Internetof Things “motes”. The work accounts for radiation from conductive antennae, from the widely used but less-well-understood dielectric antennae, and extends it into the use of piezoelectric materials – especially, films – from which the possibility of effective radiation from very small structures emerges. This note from Cambridge does not offer details such as the ratios between physical dimension and wavelength that might be possible, and refers only to “certain frequencies”; it also alludes to resonant behaviour in the piezo materials, possibly implying that any given antenna made this way might be tuned and narrow-band. The statement issued by the University includes the remarks that, “Another challenge with aerials is that certain physical variables associated with radiation of energy are not well understood. For example, there is still no well-defined mathematical model related to the operation of a practical aerial. Most of what we know about electromagnetic radiation comes from theories first proposed by James Clerk Maxwell in the 19th century, which state that electromagnetic radiation is generated by accelerating electrons. However, this theory becomes problematic when dealing with radio wave emission from a dielectric solid, a material which normally acts as an insulator, meaning that electrons are not free to move around. Despite this, dielectric resonators are already used as antennas in mobile phones, for example. “In dielectric aerials, the medium has high permittivity, meaning that the velocity of the radio wave decreases as it enters the medium,” said Dr Dhiraj Sinha, the paper’s lead author. “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.” Working with researchers from the National Physical Laboratory and Cambridge-based dielectric antenna company Antenova Ltd, the Cambridge team used thin films of piezoelectric materials, a type of insulator which is deformed or vibrated when voltage is applied. They found that at a certain frequency, these materials become not only efficient resonators, but efficient radiators as well, meaning that they can be used as aerials” Complete article, here 14 EDN Europe | MAY 2015 www.edn-europe.com


EDNE MAY 2015
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