A new type of piezoelectric composite ultrasonic transducers with high frequency in radial vibration is studied.It is composed of a piezoelectric ceramic ring and a metal disk which is inserted in the inner of the ceramic ring.First

the radial vibration of a piezoelectric ring and a metal disk is analyzed;its electro-mechanical equivalent circuit and the resonance frequency equation are obtained.It is illustrated that when the radius ratio is increased

the resonance and anti-resonance frequency of a piezoelectric ceramic ring is decreased.This means that the resonance frequency of a piezoelectric disk is larger that that of a piezoelectric ring with the same outer radius.Then

the radial vibration of the composite transducer is studied;its compound electro-mechanical equivalent circuit and the frequency equation are given.It is shown that when a metal disk is inserted into the center of a piezoelectric ring

its resonance frequency is higher than that of a piezoelectric ring or a disk.This means that the composite radial piezoelectric transducer can produce radial vibration at high resonance frequency.Experiments show that the measured resonance frequency is in a good agreement with the theoretical results.