Optimal Phase on Biaxial Driven Transducers Based Only on Electrical Power Measurements

The biaxial driving technique enhances the mechanical response of a piezoelectric actuator by dephasing two orthogonal electrical fields to the propagation and lateral electrodes. This paper presents results on the relationship between the electrical response and the phase at which the maximum acoustic efficiency was reached on a single element biaxially driven ultrasound transducer. Eight air-backed biaxial transducers $(6.4\ \text{mm}\times 6.4\ \text{mm}\times 13.7\ \text{mm})$ fabricated with hard lead zirconate titanate were used for testing. Average of the resonant frequency on propagation and lateral modes for all transducers was 133 (±0.4) kHz and 138.1 (±0.5) kHz respectively. The effective acoustic power was measured using the radiation force method and the amount of power delivered to each electrode on the biaxial transducer was varied. The results of the analysis show that the optimal phase between electrodes can be obtained by analyzing the reflected power on the lateral electrode of the biaxially driven transducer.