Broadband magnetoelectric antenna driven by multiple high-overtone bulk acoustic wave modes

Abstract High-overtone bulk acoustic waves driven magnetoelectric (ME) antennas operate in the acoustic resonant frequency range, exhibiting continuous narrowband electromagnetic radiation. ME antennas based on cooperative excitation of multiple high-overtone bulk acoustic waves are expected to achieve broadband performance and are worthy of in-depth exploration. High-overtone bulk acoustic resonator (HBAR) antennas with polished and rough acoustic reflection interfaces were fabricated and tested to investigate the influence mechanisms of acoustic modes in the HBAR on the radiation bandwidth, as well as the relationship between antenna impedance and radiation response. Far-field radiation characteristics indicate that the antenna with rough acoustic reflection interfaces featuring more high-overtone bulk acoustic wave modes suppress radiation dips of up to 5 dB at anti-resonant frequencies without sacrificing radiation gain. The radiation gain of the antenna was calculated using the gain-comparison method to be −35 dBi, with a −3 dB bandwidth of 120 MHz and a fractional bandwidth of up to 11.4%. Finally, a comparison of the radiation characteristics of the HBAR piezoelectric antenna without the magnetic film demonstrates that the broadband radiation of the HBAR ME antenna originates from dynamic magnetic flux driven by high-overtone bulk acoustic waves.