Patent ID: 6761692
Filing Date: 2004-07-13
Classification: B06B

Abstract:
An ultrasound transducer for transmission and reception of ultrasound waves through a front radiating surface in acoustic contact with a load material, where in the thickness direction normal to the front surface the transducer comprises:a transducer plate of thickness Lx, comprised of a stack of layers of films sintered together to the composite plate, the film materials having close to equal characteristic impedances so that thickness resonances of the transducer plate are determined by the total plate thickness, and a backing material of high ultrasound absorption such that reflected waves in the backing material can be neglected and having an impedance and to which the transducer plate is mounted, wherein at least one of the layers of the transducer plate is piezoelectric and has a thickness substantially smaller than the total thickness of the transducer plate, said piezoelectric layer being covered with conducting layers on both sides, and said conducting layers functioning as a 1st electrode and a 2nd electrode of an electric port to provide electromechanical coupling to thickness vibrations in the transducer in a 1st frequency band, so that efficient electro-acoustic coupling of the transducer in the 1st frequency band is obtained at frequencies at which the transducer plate is substantially thicker than half a wave length, said piezoelectric layer having a thickness of one of approximately half a wave length where the backing material has a low impedance and approximately a quarter of a wavelength where the backing material has a high impedance to obtain a thickness of the transducer plate substantially greater than half a wave length, so as to increase the mechanical stability of the plate during sintering and other handling processes and avoid contamination of said piezoelectric layer from substrate material during sintering.