Amplitude Modulation Scheme for an Acoustically Actuated Magnetoelectric Antenna Using Field-Dependent Magneto-Mechanical Effect

Mechanical antennas that are driven by external mechanical oscillation and acoustic self-resonance have been demonstrated for portable very low-frequency (VLF) electromagnetic (EM) wave transmitting. However, the mechanical relaxation, caused by the energy transition between mechanical and EM energies during signal modulation, limits the modulation rate of mechanical antennas. Here, we use direct antenna amplitude modulation (DAAM) to enhance the modulation rate of the proposed magnetoelectric (ME) antenna. First, we construct a nonlinear converse ME (CME) equivalent circuit model to optimize the dc magnetic field and operating frequency. The relaxation of Young's modulus of the magnetic layer is gradually eliminated with the increase of modulation rate until Young's modulus and radiation intensity of the ME antenna are no longer changed. Ideally, the modulation rate of DAAM is half of the carrier rate, but the actual value is lower than the ideal value due to the overshoot and ringing from the modulation coil. Under the carrier frequency of 27.6 kHz and the modulation frequency of 6 kHz, the bit rate of DAAM reaches up to 12 kbps, which is six times higher than that of the conventional electrical modulation. Our work demonstrates the potential of portable ME antenna for practical high-rate VLF EM communication.