The US Air Force Research Laboratory (AFRL) has disclosed details of research into a new generation of ultra-compact antennas that could mark a breakthrough in the miniaturisation of military and commercial communication systems.
AFRL researchers have exploited new material technologies to reduce the size of an antenna by more than 90%.
Conventional antennas rely on size to function effectively in a particular part of the radio frequency (RF) spectrum. Therefore, if the antenna is not long enough to resonate at the right frequency it will not be able to transmit or receive the desired electromagnetic waves efficiently.
Over the years, significant advances have been made in antenna miniaturisation, with mobile phones being a prime example. However, the quality of the antenna degrades as it becomes smaller, hence the need for mobile telephone network providers to put in place large numbers of cellular antenna towers to ensure adequate coverage.
To address this, researchers at AFRL's Materials and Manufacturing Directorate, working in partnership with Northeastern University, have developed an ultra-compact antenna that adopts a different approach to transmitting and receiving RF signals. “We miniaturised the antennas by borrowing a trick from acoustic filters in cellphones, which convert microwave voltages to strain waves,” said AFRL materials scientist Dr Michael McConney. “Strain waves travel much slower than the speed of light, so by doing this, we are able to shrink the wavelengths while keeping the frequency the same. This allowed us to make the antennas much smaller.”
According to the AFRL, this antenna represents a new way of thinking. By coating conventional bulk acoustic wave filters with a magnetic material, these slower strain waves can be converted into radiation, which enabled them to break the inefficient scaling laws associated with shrinking typical antennas to small sizes.
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