Synthesis of the Bandpass Filter with a Predetermined Phase Error for Generators with PLL for Piezoceramic Transducers

PLL systems are used to maintain resonance designing control systems for ultrasonic piezoelectric transducers. The nonlinear properties of piezoceramics start to affect increasing the oscillation amplitude of the ultrasonic transducer. It leads to the appearance of the second and higher harmonics of the current through the converter. It is proposed to introduce an active fourth-order bandpass filter (consisting of two second order filters) into the feedback circuit to eliminate errors. Almost flat phase response allows minimizing the phase error in PLL lock range. The synthesis technique and simulation results of such filter are given in this work.