Ingestible size continuously transmitting temperature monitoring pill

• US 4,844,076 A
• Filed: 08/26/1988
• Issued: 07/04/1989
• Est. Priority Date: 08/26/1988
• Status: Expired due to Term

• Current Assignee: Johns Hopkins University of Baltimore Maryland
• Original Assignee: Johns Hopkins University
• Inventors: Lesho, Jeffery C., Hogrefe, Arthur F.
• Primary Examiner(s): Cohen, Lee S.
• Assistant Examiner(s): GETZOW, SCOTT M
• Application Number:
  US07/236,885
• Time in Patent Office: 312 Days
• Field of Search: 128/736, 128/631, 128/903, 340/870.17, 340/573, 331/66
• US Class Current: 600/302
• CPC Class Codes: A01K 11/007 Boluses
• CPC Class Codes: A61B 2018/1435 Spiral
• CPC Class Codes: A61B 2560/0219 of externally powered implanted units
• CPC Class Codes: A61B 5/0008 Temperature signals
• CPC Class Codes: A61B 5/073 Intestinal transmitters
• CPC Class Codes: A61B 5/6861 Capsules, e.g. for swallowing or implanting
• CPC Class Codes: G01K 1/024 for remote indication
• CPC Class Codes: G01K 7/32 using change of resonant frequency of a crystal
• CPC Class Codes: Y10S 128/903 Radio telemetry

Abstract

A temperature responsive transmitter is disclosed. The transmitter utilizes a unique circuit design that allows encapsulation in an ingestible size capsule. The inventive circuit design uses a one transistor inverting amplifier with a tank circuit forming the link between the transistor'"'"'s collector and the battery. The tank circuit is tuned to provide a lagging capacitive load which causes the inverting amplifier to oscillate. The tank circuit contains a coil inductor that emits a near field magnetic communications field containing temperature information. The ingestible size temperature pill can be configured in a rechargeable embodiment. In this embodiment the pill uses the inductive coil in the tank circuit as the magnetic pickup to charge a rechargeable nickel cadmium battery.

Claims

1. A miniaturized temperature responsive transmitter comprising:

a battery providing a voltage V_b ;

reed-switch means adapted to be controlled by a magnet to disconnect the battery during storage;

a one-transistor inverting amplifier having an input and output and operably biased to said battery;

a temperature-sensitive crystal operably coupled between said input and output of said inverting amplifier and having a natural frequency dependent on local temperature;

a tank circuit having an inductor and a capacitor, operably coupled between said output of said inverting amplifier and said battery and tuned to a frequency lower than the natural frequency of said temperature-sensitive crystal for both providing a lagging phase shift at the output of said inverting amplifier and for emitting a near field magnetic signal from said inductor, wherein the frequency of said near field magnetic signal is dependent upon the frequency of the temperature sensitive crystal which is temperature dependent, and wherein said inverting amplifier acts as a switch causing said capacitor to charge and discharge through said inductor, thereby allowing the tank circuit to operate at 2 V_b peak-to-peak volts.

2. The apparatus of claim 1, wherein said tank circuit is connected between the collector of said transistor amplifier and said battery, and said temperature sensitive crystal is connected in the collector/base circuit of the one-transistor amplifier.

3. The apparatus of claim 2, wherein said battery is a one-cell battery.

4. The apparatus of claim 2, wherein said temperature sensitive crystal is operating in a Pierce oscillator configuration.

5. The apparatus of claim 2, wherein a separate RC network is connected to the collector/base circuit of the one transistor amplifier to provide an additional lagging phase shift.

6. The apparatus of claim 3, wherein said battery is a nickel cadmium battery.

7. A rechargeable, miniaturized temperature responsive transmitter comprising:

a rechargeable battery;

an inverting amplifier having an input and output and operably biased to said battery;

a temperature sensitive crystal operably coupled between said input and output of said inverting amplifier and having a natural frequency dependent on local temperature;

a tank circuit having a first and second terminal with an inductive coil connected therebetween, the first terminal of said tank circuit being connected to said inverting amplifier;

a current limiting device connecting said second terminal of said tank circuit to said battery, for limiting the current that can flow into said rechargeable battery;

a charging capacitor connected between said second terminal of said tank circuit and ground for storing electrical energy picked up by said inductor;

a diode connected between said first terminal of said tank circuit and said ground for rectifying full wave oscillation picked up on the inductor and for charging said charging capacitor; and

,

wherein said tank circuit is tuned to a frequency lower than the natural frequency of said temperature sensitive crystal, and wherein said tank circuit performs the following functions;

i. providing a lagging phase shift at the output of said inverting amplifier;

ii. emitting a near field magnetic signal from said inductor at a frequency dependent on the temperature sensitive crystal which is temperature dependent; and

,

iii. a power pickup used to recharge the rechargeable battery.

8. The apparatus of claim 7, wherein said inverting amplifier is a one transistor amplifier with said tank circuit connected between the collector of said transistor amplifier and said rechargeable battery and said temperature sensitive crystal is connected in the collector/base circuit of said one-transistor amplifier.

9. The apparatus of claim 8, wherein said battery is a onecell battery.

10. The apparatus of claim 8, wherein said battery is a rechargeable nickel cadmium battery.

11. The apparatus of claim 8, wherein said temperature sensitive crystal is operating in a Pierce oscillator configuration.

12. The apparatus of claim 8, wherein a separate RC network is connected in the collector/base circuit of the one transistor amplifier to provide an additional lagging phase shift.

13. The apparatus of claim 8, wherein said current limiting device is a JFET that causes current limiting only when the voltage of the inductive coil is more positive than the rechargeable battery.

14. An ingestible temperature sensing pill comprising:

a first cylinder of epoxy encompassing a battery and a transmitter/sensitive circuit, said transmitting/sensing circuit including;

an inverting amplifier having an input and output and powered by said battery;

a temperature sensitive crystal operably coupled between said input and output of said inverting amplifier and having a natural frequency dependent on local temperature,

a tank circuit having a coil inductor, operably coupled between said output of said inverting amplifier and said battery and tuned to a frequency lower than the natural frequency of said temperature sensitive crystal for both providing a lagging phase shift at the output of said inverting amplifier and for emitting a near field magnetic signal from said coil inductor, wherein the frequency of said near field magnetic signal is dependent upon the frequency of the temperature sensitive crystal which is frequency dependent,

wherein said coil inductor being wrapped around said first epoxy cylinder but not encompassing said battery;

a second epoxy shell encompassing said first cylinder of epoxy and said coil inductor, and,

an outer coating of biocompatible material covering said second epoxy shell.

15. The apparatus of claim 14, wherein said inverting amplifier is a one transistor amplifier with the tank circuit connected between the collector of said transistor amplifier and said battery and said temperature sensitive crystal is connected in the collector/base circuit of said one transistor amplifier.

16. The apparatus of claim 14, wherein said sensing pill is shaped to form an ingestible capsule.

17. The apparatus of claim 14, wherein said outer coating of biocompatible material is an outer coating of silicone rubber.