MINIATURE MULTICHANNEL BIOTELEMETER SYSTEM

• US 3,815,109 A
• Filed: 07/05/1972
• Issued: 06/04/1974
• Est. Priority Date: 07/05/1972
• Status: Expired due to Term

• Current Assignee: Joe T. Sumida, John B. Carraway
• Original Assignee: Joe T. Sumida, John B. Carraway
• Inventors: Carraway, John B., Sumida, Joe T.
• Primary Examiner(s): Yusko, Donald J.
• Assistant Examiner(s): Mooney, Robert J.
• Application Number:
  US05/269,073
• Time in Patent Office: 699 Days
• Field of Search: 340/207,203,183 128/2.1A 325/113,141
• US Class Current: 340/870.12
• CPC Class Codes: A61B 5/0002 Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network A61B5/07 takes precedence; transmission systems for measured values G08C; transmission H04B; transmission of digital information H04L; wireless communication networks H04W
• CPC Class Codes: G08C 15/08 the signals being represented by amplitude of current or voltage in transmission link
• CPC Class Codes: Y10S 128/903 Radio telemetry

Abstract

A miniature multichannel biotelemeter system includes a transmitter unit in which signals from different sources are sampled to produce a wavetrain of pulses in which sample pulses of all the signals are separated by sync pulses. The pulses amplitude modulate a radio frequency carrier which is received at a receiver unit. Therein the sync pulses are detected by a demultiplexer which routes the pulses from each different source to a separate output channel wherein the pulses are used to reconstruct the signals from the particular source.

Claims

1. A multichannel biotelemetry system for transmitting physiologicaL signals from a biological subject to a remotely located receiver unit, whereat the signals are reconstructed, the system comprising:

a transmitting unit adapted to be carried by said subject and including a plurality of signal channels, each adapted to receive physiological signals from said subject, a common terminal, means for sequentially sampling the signals in each of said channels and a predetermined potential level for producing at said common terminal a composite wavetrain of equal duration pulses which includes a set of pulses representing samples of the signals in all of said channels between successive synchronizing pulses of substantially said predetermined potential level, and transmitter means connected to said common terminal for transmitting radio carrier signals of a frequency which is modulated by the pulses in said composite wavetrain of pulses; and

a remotely located receiving unit including means for receiving the frequency modulated radio carrier signals and for extracting the composite wavetrain of pulses therefrom, means responsive to the synchronizing pulses in said composite waveform of pulses for generating a sequence of equal duration local sync pulses, in time coincidence with substantially the midpoints of the pulses in said received composite wavetrain of pulses and of durations which are shorter than one-half the durations of the pulses in said received composite wavetrain of pulses, a plurality of output means associated with the channels in said transmitting unit and means for utilizing said local sync pulses to supply to each of said output means only portions of the received pulses representing samples of the signals in a different one of said channels in said transmitting unit, each of said output means providing an output corresponding to the signals in the channel with which it is associated.

2. In a system as described in claim 1 wherein said means for sequentially sampling, sample the signals in each channel at the same sampling rate which is a function of the upper frequency limits of the signals in said channels.

3. In a system as described in claim 1 wherein said means for sequentially sampling include a gate between each channel and said common terminal, and a gate between a source of said predetermined potential level and said common terminal, and a sequencer for sequentially enabling said gates to apply to said common terminal a potential of an amplitude and polarity which is a function of the signal in one of the channels when a gate connected to one of said channels is enabled or said predetermined potential level when the gate between the common terminal and said source is enabled.

4. In a system as described in claim 3 wherein at least one of said channels includes a filter for limiting the frequencies of the signals sampled when the gate connected to the channel is enabled to be not greater than one half the rate at which each of said gates is enabled.

5. In a system as described in claim 3 wherein each channel includes an input terminal at which signals from said subject are applied and a filter and amplifier connected in series between said input terminal and the gate associated with the channel, for filtering said signals at said input terminal so as to limit at least their upper frequency not to exceed one half the rate at which said gate is enabled and for amplifying the filtered signals by a selected amplification factor.

6. In a system as described in claim 3 wherein each of said output means in said receiving unit includes means for holding successive samples supplied thereto and a filter coupled to said means for holding to provide a smoothed output signal as a function of the samples in said means for holding.

7. A system as described in claim 6 wherein said means for utilizing said local sync pulses comprises a plurality of switchable gates and a sequencer for sequentially enabling said switchable gates so that successive samples from the same channel in said transmitting unit are suCcessively supplied to the means for holding associated with the same channel.

8. A method of monitoring physiological signals from a biological subject that is unrestricted by wires extending from the subject to monitoring means, the steps comprising:

sampling in a subject-carried unit each of a plurality of physiological signals from the subject at a preselected rate, each sample being in the form of a pulse whose amplitude and polarity are related to the physiological signal at the time of sampling;

generating synchronizing pulses in said subject-carried unit;

combining the sample pulses with the synchronizing pulses into a composite wavetrain of pulses of equal durations in which successive synchronizing pulses are separated by at least a set of pulses which includes a sample pulse of each of said physiological signals;

frequency modulating a radio-frequency carrier with the pulses of said composite wavetrain of pulses;

transmitting the frequency modulated radio frequency carrier to a remotely located receiving unit;

extracting at said receiving unit the pulses of said composite wavetrain from the frequency modulated radio frequency carrier; and

utilizing at said receiving unit the received synchronizing pulses to form a sequence of local sync pulses of equal durations which are shorter than the durations of the pulses of said composite wavetrain, with the midpoint of each local sync pulse being substantially in time coincidence with the midpoint of a different pulse in said wavetrain; and

utilizing said local sync pulses to form an output signal corresponding to each physiological signal from the sample pulses thereof, contained in said composite wavetrain of pulses.

9. The method as described in claim 8 wherein each physiological signal is sampled at a rate which is at least twice as high as its upper frequency limit.

10. The method as described in claim 8 wherein in said receiving unit the local sync pulses are utilized to control the routing of portions of successive sample pulses from the same physiological signal to a different output channel, and holding and filtering the sample pulses in each output channel to produce an output signal therefrom.

11. The method as described in claim 10 wherein each physiological signal is sampled at a rate which is at least twice as high as its upper frequency limit.