Ultrasonic transducer with improved bandwidth using phase shift interference in the backing

High quality two dimensional ultrasound echo amplitude images require an ultrasonic transducer capable of emitting short acoustic pulses. Traditionally the transducer impulse response in the time and frequency domains is controlled by the choice of the backing material and/or the number of the front impedance matching layers. However, the availability of the suitable materials and suitable fabrication process introduces limitations when trying to control the transducer impulse response by controlling the number of front impedance matching layers. In this paper an alternative method for controlling the transducer impulse response is presented. In this technique staggered delay sections are placed in the backing layer in a checkerboard pattern. These delay sections are composed of inert piezoelectric material with accurate thickness to control the transducer impulse response in the time and consequently frequency domain. The alternating delay sections result in two reflections between the backing and the piezoelectric ceramic layer interface with controlled alternating delay phase shift to control the transducer impulse response. The appropriate length, width and pitch of the delay section results in a constructive and destructive interference along the length of the pulse controlling the shape of the emitted pulse in the time and frequency domains