A frequency tunable low-noise YIG-GGG based oscillator with strong magneto-elastic coupling

TL;DR

This paper introduces a frequency tunable, low-noise magneto-acoustic oscillator based on a YIG-GGG resonator, achieving high magneto-elastic coupling and simplified design with discrete and continuous frequency tuning capabilities.

Contribution

The work demonstrates a novel YIG-GGG based oscillator with strong magneto-elastic coupling, enabling simplified design and tunable low-noise operation in the 1-2 GHz range.

Findings

Achieved magneto-elastic coupling of around 1 MHz.

Demonstrated discrete frequency tuning with 3.281 MHz steps.

Improved phase noise by 30 dB in low-noise regime.

Abstract

We present a frequency tunable magneto-acoustic oscillator (MAO) operating in low-phase-noise and complex dynamical regimes based on a single composite YIG-GGG resonator. The magneto-acoustic resonator (MAR) is based on a YIG (yttrium iron garnet) layer epitaxially grown on a GGG (gadolinium gallium garnet) substrate. By optimizing the YIG thickness, we obtain a high magneto-elastic coupling of around 1 MHz between the ferromagnetic resonance (FMR) in YIG and high overtone acoustic resonances (HBARs) in the YIG-GGG structure in the 1-2 GHz frequency range. It allows to eliminate the need for pre-selectors and bulky circulators, thus simplifying the MAO design while maintaining the possibility to lock to HBAR YIG-GGG modes. With an adjustment in the loop over-amplification parameter, the MAO can be locked either only to high-Q magneto-acoustic HBARs or to both types of resonance including HBARs and the FMR mode of the YIG film. In a low-phase-noise regime, MAO generates only at certain values of the applied field and exhibits discrete frequency tunability with a 3.281 MHz step corresponding to the frequency separation between the adjacent HBAR modes in a YIG-GGG structure. In a complex regime where oscillation conditions expand to include both HBAR and FMR modes, MAO demonstrates continuous generation as the function of the applied field with variable phase noise parameters. Moreover, in low-phase-noise regime, MAO phase noise plot improves by 30 dB compared to the operational regime locked to the pure FMR in YIG which is in agreement with the measured FMR and HBAR Q-factors.