Noise rejecting detector for biomedical signals

DETAILED DESCRIPTION It is an object of the present invention to overcome the difficulties of the prior art by providing an improved biological signal detector which is extremely sensitive, yet resistant to the effects of high frequency noise.
In the preferred embodiment, a plurality of biosensors are used to obtain an electrical representation of the alternating component of the pulsatile portion of biological signals of interest.
Conventional control circuitry is employed to cause the individual biosensors to sample a particular biological signal during predetermined time intervals to obtain a sequence of non-continuous pulse amplitude signals representing the amplitude of the biological signal.
The signal detected by each biosensor during the sampling interval is comprised of a direct current component, an alternating component at a first frequency and an alternating current noise signal component at a second frequency.
The noncontinuous amplitude signals produced by each of the biosensors during the respective time intervals are combined to produce a multiplexed signal representation of the plurality of biological signals.
In the preferred embodiment of the invention, the multiplexed signal representation of the biological signals is demultiplexed by a detector circuit comprising a plurality of switches each of which controls an individual storage network.
A switch logic control circuit synchronizes the various switches to close during the time intervals corresponding to the pulse amplitudes representing the particular signal of interest.
The amplitude of the alternating component of each of the biological signals is stored in one of the respective storage networks over a number of pulse time intervals.
In the preferred embodiment, the storage networks of the detector each comprise a resistor and capacitor having an RC constant which is purposely chosen to be substantially longer than the time interval of the pulses.
The long time constant of the storage networks allows the detector circuit to track changes in amplitude which manifest themselves over a relatively large number of time intervals, but prevents the detection of high frequency noise signals which may be present during the sampling intervals