LL-type filter for piezoelectric transducer

Basic principles of LL-type filter modeling and design for piezoelectric transducers are considered. Part of piezoelectric transducer equivalent circuit was integrated with LL-filter scheme and presented in the form of equivalent quadripole. The mechanical transducer resistance is equivalent quadripole load. The analysis proves that the usage of LL-type matching filter allows piezoelectric transducer working both at the resonance frequency and at the parallel resonance frequency. Herewith the mechanical oscillation amplitude is smaller than in the case with L-type matching filter. The minimum of the input impedance doesn't coincide with the mechanical resonance frequency. The theoretical results are confirmed with sufficient accuracy with the experimental verification. It was found that signal proportional both to input filter current and to current of mechanical branch can be used as feedback signal.