Modeling of Multiferroic Antennas in the Akhiezer Regime: Effects of Acoustic Resonator Excitation and Topology on Radiation

A 2-D closed-form model of multiferroic antennas in the GHz range is proposed. The model predicts the electrical and mode shape responses of film bulk acoustic resonators (FBARs) and solidly mounted resonators (SMRs) and provides a closed-form solution of the radiated electromagnetic (EM) field, enabling optimization of antenna parameters to maximize radiated power. Furthermore, the model is exploited to analyze the radiation performance of multiferroic antennas according to acoustic resonator topologies (FBAR and SMR) and excitation modes (thickness-extensional (TE) and thickness-shear (TS) modes). The analysis reveals that SMR-based antennas radiate less than FBAR-based ones due to substrate energy loss. In addition, antennas excited by TE modes can generate significantly more power than those excited by TS modes. Finally, we investigate the frequency-dependent mechanical and electrical limitations of radiation at GHz frequencies by comparing the efficiency-bandwidth products of different multiferroic antennas with Chu’s limit in the Akhiezer regime. The results suggest that phonon-phonon coupling of Akhiezer damping will be the primary limiting factor of antenna radiation at GHz frequencies, rather than Chu’s limit.