Turuvekere R. Gururaja

Ultrasonic transducer having two or more resonance frequencies

A transducer for transmitting and receiving ultrasonic energy at more than one frequency includes first and second electrostrictive layers mechanically coupled together such that ultrasonic vibrations in one layer are coupled into the other layer. The first electrostrictive layer is laminated between upper and middle electrical contact layers, and the second electrostrictive layer is laminated between middle and lower electrical contact layers. A bias voltage arrangement selectively produces within the first and second electrostrictive layers electric fields oriented in opposite directions or electric fields oriented in the same direction. When the electric fields are oriented in opposite directions, the transducer has a first resonance frequency. When the electric fields are oriented in the same direction, the transducer has a second resonance frequency. By selecting the number of electrostrictive layers in a transducer and by selecting the thicknesses of different layers, a transducer having two or more different desired resonance frequencies may be produced.

Electrostrictive ultrasonic probe having expanded operating temperature range

An ultrasonic electrostrictive transducer for transmitting and receiving ultrasonic energy and having an expanded operating temperature range, preferably about room temperature. The transducers may be made from PMN-PT solid solutions having select mole percentages of PT and being doped with La, whereby the operating temperature range about a given operating temperature may be effectively doubled.

Apparatus and methods for controlling sensitivity of transducers

Apparatus and methods for controlling electrostrictive transducer sensitivity in a pulse-echo medical ultrasound system. Certain characteristics of each transducer element are tested after manufacture and recorded on a storage medium. The stored data is then used, along with certain model relations, for monitoring certain operational parameters of the transducer during use, and feedback compensation applied for maintaining the transducer sensitivity substantailly constant. The parameters to be monitored may include the temperature, acoustic pressure, input power, and a figure of merit determined from the dielectric constant and coupling coefficient.