Magnetically tunable 4 × 2 encoder utilizing Terfenol-D-embedded phononic crystal ring resonators

Abstract

The research nominates an innovative magnetically tunable 4×2 encoder structure that utilizes ring resonators and Terfenol-D tubes embedded inside a robust phononic crystal made of solid materials. The proposed method takes advantage of the variable magnetic field strengths of Terfenol-D in the MHz frequency spectrum through wave interference techniques. The encoder system is designed as a two-dimensional phononic crystal, using poly methyl methacrylate as the foundational material, and integrates a square arrangement of circular tungsten tubes. The encoder features an ultra-compact footprint of 125 × 10^-6 m², with four input waveguides and two output waveguides, each equipped with a pair of ring resonators. The smaller cavities are coupled with curved two-branch waveguides, optimizing wave interference while minimizing losses and scattering to achieve enhanced performance. Each ring resonator incorporates three integrated Terfenol-D tubes, which modulate their Young's modulus properties. The symmetrical design of the structure enables the generation of distinct resonant frequencies under varying magnetic field intensities. The resonance frequencies of the ring resonators, along with the dynamic adjustment of the Terfenol-D cylinders, significantly influence the encoder's operational efficiency and tunability. Tunability experiments are conducted for three distinct Young's modulus values of Terfenol-D, corresponding to three various magnetic fields, resulting in resonance frequencies of 1.7388 MHz, 1.7389 MHz, and 1.7390 MHz. The encoder's performance was assessed through the application of the finite element method, yielding an average contrast ratio of 10.16 dB. This proposed encoder offers a straightforward and effective solution for acoustic communication systems and networks, demonstrating significant potential for practical applications.