DETAILED DESCRIPTION Turning now to the details of the drawings, FIG.
1 is a functional block diagram illustrating a conventional Doppler ultra-sound monitor system.
The device operates on the principle that ultrasound energy incident upon a moving surface will be reflected thereby, and the reflected ultrasound signal will experience a change in frequency which is proportional to the rate of movement of the surface.
FIG.
1 illustrates such a monitor system 10 including a transducer 12 in contact with a living body B, within which heart rate is to be detected.
Transducer 12 is a conventional ultrasonic transducer which may be electrically excited to generate ultrasound energy, and, in response to incident ultrasound energy, emits an electrical signal.
An electrically actuated transmitter 14 is electrically coupled to transducer 12 and, when actuated, causes the transducer to emit ultrasonic energy.
On the other hand, when ultrasonic energy impinges on transducer 12, the transducer emits an electrical signal which is coupled to receiver 16.
This signal is an electrical representation of the ultrasonic energy incidence on transducer 12 and, therefore, has a frequency variation which is proportional to the rate of movement of the incident surface in the body (in this case, on appropriate wall of the heart).
This electrical signal is appropriately filtered and amplified by receiver 16 and is supplied therefrom to a frequency demodulator 18, which, as is well-known, produces a demodulated signal which both amplitude (e.
g.
voltage) and frequency information.
The demodulated signal therefore be used to obtain a direct indication of heart rate.
After filtering by main filter 20, which provides a degree of cleaning or smoothing, the signal is in appropriate condition for application to a utilization device, such as some form of display or meter.
In FIG.
1, transducer 12 is coupled to transmitter 14 and receiver 16 through a double line.
As a convention, such a line will represent a duplex connection
|
Communications 
