Method and a means for determining ultrasonic wave attenuation in tissue using zero crossing detector functioning within a specified frequency band

摘要

A zero crossing detector including timing and logic circuitry for ascertaining and eliminating undesirable waveform characteristics. If a zero crossing indication occurs within a set time period after a trigger event due to a phase inversion or noise, then the indication is ignored. Conversely, if a zero crossing does not occur within a second set time period due to a phase reversal, an artificial crossing will be indicated. By establishing these bounds, the system will function within a specified frequency band.