Wavelength Miniaturized

Radio waves interact with much smaller acoustic waves in a micro-manufactured material to realize miniaturized transmit or receive antenna. paper


Antennas that interconvert between alternating electric currents and electromagnetic (EM) wave radiation, act as an omnipresent critical component in smart phones, tablets, radio frequency identification systems, radars, etc. One of the key challenges on state-of-the-art antennas lies in their size miniaturization. Compact antennas rely on an EM wave resonance, and therefore typically have a size of more than λ/10, that is one-tenth of the EM wavelength λ. The limitation on antenna size miniaturization has made it very challenging to achieve compact antennas and antenna arrays, particularly at VHF and UHF with large λ, thus putting severe constraints on wireless communication systems and radars on mobile platforms. New antenna concepts need to be investigated with novel EM waves radiation and reception mechanisms for the reduction of antenna size.

On the other hand, strong strain-mediated magnetoelectric (ME) coupling in magnetic/piezoelectric heterostructures has been recently demonstrated which enables efficient energy transfer between magnetism and electricity. The strong ME coupling, if realized dynamically at radio frequencies (RF) in ME heterostructures, could enable voltage induced RF magnetic currents that radiate EM waves, and acoustically actuated nanoscale ME antennas with a new receiving and transmitting mechanism, for EM waves. This concept has recently been theoretically proposed. However, despite of the moderate interaction between the surface acoustic wave and magnetization, strong ME effect has only been demonstrated at kHz frequencies, or in a static or quasi-static process. Here one question naturally arises: Is it possible to realize efficient energy coupling between bulk acoustic waves and EM waves in ME heterostructures at RF frequencies through ME coupling? Based on our results in this work, we can answer this question affirmatively.

Here we demonstrate the nanoelectromechanical system (NEMS) antennas operating at VHF and UHF frequencies based on the strong ME coupling between EM and bulk acoustic waves in the resonant ME heterostructures (ferromagnetic/piezoelectric). These ME antennas have realized acoustic transmitting and receiving mechanisms in nanoplate resonators (NPR) and thin-film bulk acoustic wave resonators (FBAR). During the receiving process, the magnetic layer of ME antennas senses H-components of EM waves, which induces a oscillating strain and a piezoelectric voltage output at the electromechanical resonance frequency. Conversely, during the transmitting process, the ME antennas produces an oscillating mechanical strain under an alternating voltage input, which mechanically excites the magnetic layer and induce a magnetization oscillation, or a magnetic current, that radiates EM waves. Therefore, these ME antennas operate at their acoustic resonance instead of, EM resonance. Since the acoustic wavelength is around five orders of magnitude shorter than the EM wavelength at the same frequency, these ME antennas are expected to have sizes comparable to the acoustic wavelength, thus leading to orders of magnitude reduced antenna size compared to state-of-the-art compact antennas.


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