IEEE Future Directions
Related Articles
Wireless communications is about translating an electrical signal flowing in a wire into an electromagnetic signal that can travel through the air. This is done using an antenna. Of course it has to be done twice, once to convert the electrical signal into an electromagnetic wave propagating in the air and then to capture the electromagnetic wave and convert it into an electrical signal that can be processed.
The antenna is the perfect tool for such a conversion and it works on the physical principle of electromagnetic resonance. In order to work the antenna should have a length that is at least 1/10 of the wavelength, but in practice you want to have an antenna that is at least half wavelength to capture (or transmit) the signal efficiently. For a smart phone, operating in the GHz range it means a length of the order of 15 cm (and that is what you have, with the antenna bent around the phone, you might also have noticed antitheft tags that have a sort of spiral embedded – that is the antenna wrapped up on itself).
The length of the antenna is an issue in some IoT and in several applications where size is constrained.
Researchers at Northeastern University have come up with a different sort of antenna that operates the transformation using acoustic resonance. This allows the construction of antennas that are thousands of times smaller.
They have experimented with a circular antenna, one mm in size, demonstrating its capability to receive signals transmitted in the GHz range and a rectangular one, still on mm in size, that is able to receive signals transmitted in the MHz range.
These new types of antennas, called nanomechanical magnetoelectric (ME) antennas, receive and transmit the electromagnetic wave exploiting the ME effect at their acoustic resonance frequencies. The acoustic waves in the ME stimulates magnetisation oscillation in a ferromagnetic thin field that radiates the electromagnetic field (transmission). When operating as receiver the ME senses the magnetic field and provides an electrical signal through a piezoelectric effect.
The researchers are confident that these antennas can be used in bioimplants, providing a wireless communication channel with chips implanted in the brain, a breakthrough, since progress in brain implant has been constrained by the need of using wires to connect the implant with the external devices and this leads to potential risk of infection.
On the other hand, in the future, we will not have any hint that the person we are talking to is actually an augmented human with an implanted chip in her brain!
