Broadband Electrically Small Antennas with Strain Powered Multiferroics

Antennae built from magnetic materials offer a promising concept for reducing antennae’s size to below free space wavelengths (i.e. < λ/50). However, recent studies on strain mediated multiferroic antenna heterostructures show only narrow band operation. To overcome this issue, we studied a system consisting of a magnetoelastic single domain disk placed atop a piezoelectric substrate. The spinning magnetization radiates electromagnetic energy into free space over broadband frequencies, i.e. from very-high frequency to ultra-high frequency. The magnetization is driven with patterned electrodes with periodic input voltages, which produce strain that couples to the magnetoelastic media. Two magnetoelastodynamic modeling approaches were used; one within a micromagnetic finite element formulation and the other in a macro spin framework. The free space radiation is modeled by considering two orthogonal magnetic dipoles rotating out of phase.
We studied magnetic materials with frequencies ranging from 10 MHz to 2 GHZ, which show similar results for the dynamics. These results are used in an analytical formulation to predict radiation power densities of ~mW/m². Arraying these elements produces larger radiation magnitudes, suggesting a new path for creating small broadband antennae.