The mechanical motion of permanent magnets is crucial in applications such as motors, wireless power transfer, communication systems, and biomedical devices. These systems often rely on either resonant oscillatory motion or continuous rotational motion of permanent magnets, with performance and stability influenced by factors like temperature variations, material properties, and nonlinear effects. In this paper, we introduce an adaptive driving circuit using a negative impedance converter (NIC) that autonomously sustains resonance or continuous rotation in magneto-mechanical systems without the need for sensors or active tuning. The NIC-based driving circuit also incorporates a saturable gain to regulate and maintain the desired oscillation amplitude and rotational speed using simple DC voltage control. Experimental results validate the system's ability to maintain resonance or continuous rotation under varying conditions, demonstrating the robustness and practicality of this driving circuit.

Magneto-mechanical transmitters (MMTs) are of active interest for ultra-low-frequency (ULF) communication, as they can significantly reduce the power consumption and size requirements compared to conventional ULF antennas. Typical MMTs produce ULF signals through either oscillatory or continuous rotational motion of permanent magnets. In this paper, we present an adaptive driving circuit that uses a negative impedance converter (NIC) to autonomously sustain motion for both resonant and continuous rotation MMTs without the need for sensors or active tuning. The driving circuit adapts seamlessly to a wide range of resonant frequencies and rotational speeds, ensuring consistent performance across different MMT configurations without altering the system's inertia or stiffness. Additionally, it features a saturable gain mechanism that regulates the oscillation amplitude and rotational speed using DC voltage control, which can be used for amplitude and frequency modulation.

Magneto-mechanical resonator arrays have emerged as a promising transmitter solution for compact ultra-low frequency (ULF) wireless communication systems and can be extremely power-efficient compared to traditional electrical antennas in the ULF range. The efficiency of ULF signal generation using magneto-mechanical transmitters (MMTs) is dictated by multi-physical effects from mechanical, magnetic, and electrical domains, leading to an interesting trade space. In this work, we show that an MMT’s most power-efficient and most voltage-efficient driving frequencies always differ, forcing designers to sacrifice one efficiency for the other. To address this issue, we propose an efficiency optimization method that minimizes the total impedance of the MMT at the most power-efficient driving frequency, by means of a compensation capacitor added to the electromagnetic actuation coil system. Our experimental results show excellent agreement with our analytical model, and we demonstrate that our approach enables simultaneous maximization of voltage and power efficiencies of an MMT at the same driving frequency. We additionally describe how to apply this optimization method on multi-resonator magneto-mechanical arrays and present numerical analysis that predicts much greater improvement factors in systems having larger net magnetic moments and drive coils with larger sizes.