Directional doppler ultrasound systems for biosignal acquisition and

Abstract

A directional doppler ultrasound system for biosignal detection and acquisition, particularly for use in fetal monitoring, for example, prior to and during labor and preferably employing a wide beam transducer arrangement, the system enabling operator selection of signals effected by physiologic events having associated therewith motion in given different directions (i.e., the towards and away directions relative to the transducer arrangement). Such a system employs a pair of mixers in which the receive echoes of the transmitted carrier signal are beat with a portion of the carrier signal then being transmitted, wherein the carrier signal input to one of the mixers is phase shifted by 90.degree. relative to the other. The mixer outputs are passed through a constant 90.degree. phase difference network where one input receives a 90.degree. phase shift relative to the other, and both are then coupled to sum and difference amplifiers to provide respective towards and away directional doppler information. In a preferred embodiment the directional system is combined with a doppler ultrasound system employing ranging techniques to provide an overall system having a capability of delivering either or both of a pair of outputs comprising the doppler components of interest in the received echoes which are representative of movement within a selected volume remote from the operative location of the transducer arrangement and selectively associated to the towards and away directions relative to the latter.