Smart generator for ultrasonic applications

This paper presents the first results for the design of an optimized generator for an ultrasonic transducer. This emitter/receptor works within the frequency range of 1 to 10 MHz. The generator output impedance equals 50 Omega and the generator itself delivers burst wave signals at a controlled fundamental frequency. The generator structure, with a negative feedback, guarantees that the optimal excitation frequency is detected. The control unit utilizes the characteristics of the transducer impedance. Optimization is carried out by an automatic search of the parallel resonance frequency for which the impedance of the transducer is maximum. We evaluate the impedance module from the envelope of the signal present at the transducer input. The criterion to be maximized is the level of the envelope in established mode. The detection of the optimal frequency is based on the iterative algorithm of the gradient in which the frequential step is functional to the criterion differential. The results, carried out initially on a electric model of a transducer, give a settling time of one millisecond for a frequential resolution of 3 KHz around the optimal frequency