Chirp Focused Transmitter Theory

Abstract

We have described an electronically focused and scanned acoustic imaging device in earlier papers.^1,2 This device was constructed by using a tapped acoustic surface wave delay line as a phase reference for an array of piezoelectric transducers. By inserting a frequency modulated chirp along the delay line, the device can be used either as a receiver or as a transmitter. In the transmit mode, it acts like a moving lens, emitting a focused beam which scans along a plane parallel to the array at a velocity comparable to the acoustic velocity. The same array can be used in the receive mode. By this means, a B-scan device was constructed which has good transverse and range definition..