Method and apparatus for transducer excitation in medical ultrasound imaging

A method of transducer excitation in a medical ultrasound imaging system having a waveform generator and a transducer, the method comprising the steps of:

• (a) generating by the waveform generator an excitation waveform signal with three base waveforms (A, B, C), each of which is a unipolar pulse, wherein the waveform signal represents a gated, stepped approximation of a Gaussian envelope multiplied by a cosine carrier signal, with said three base waveforms satisfying the relationships of:
• voltage-time product of positive (A+B)=negative C, where C the first base waveform comprises first and second pulses having the same duration of T1=0.375 T0;
• wherein said second base waveform (A) and said third base wave form (B) has the same duration with the center of said second base waveform (A) shifted from the center of said third base waveform (B);
• (b) selecting a carrier frequency signal, F0, in accordance with a fundamental frequency of the transducer, F0=1/T0;
• and
• (c) applying the excitation waveform signal to the transducer.

An ultrasound transmitter for generating an excitation waveform with programmable apodization and time (phase) shift, the transmitter comprising:

• a phase locked loop (PLL) generating a clock signal with user-selectable phase shift in response to a reference clock having a frequency 8×F0, where F0 is a fundamental frequency of the transducer;
• a waveform generator having a plurality of waveform outputs for providing respective waveforms in response to a trigger signal and the clock signal, and constructing an excitation waveform, with three base waveforms (A, B, C), each of which is a unipolar pulse, with said three base waveforms satisfying the relationships of:
• voltage-time product of positive (A+B)=negative C, where C comprises two pulses having the same duration;
• wherein the waveform represents a gated, stepped approximation of a Gaussian envelope multiplied by a cosine carrier;
• selecting the carries frequency, F0, in accordance with a fundamental frequency of the transducer;
• first, second and third programmable current drivers each having a waveform input and having a current output, and providing current signals from the current output in response to a voltage reference and a respective waveform applied to a corresponding waveform input from a corresponding waveform output of the waveform generator;
• a power amplifier for generating an excitation waveform in response to current signals on the current outputs of the current drivers;
• and
• a first and second command registers controlling said apodization factor and time (phase) shift of the excitation waveform.