RADIO CAPSULE OSCILLATOR CIRCUIT

• US 3,739,279 A
• Filed: 06/30/1971
• Issued: 06/12/1973
• Est. Priority Date: 06/30/1971
• Status: Expired due to Term

• Current Assignee: David L. Hollis
• Original Assignee: David L. Hollis
• Inventors: Hollis, David L.
• Primary Examiner(s): Mayer, Albert J.
• Application Number:
  US05/158,251
• Time in Patent Office: 713 Days
• Field of Search: 128/2P,2R,2.5P,2.1A 325/113 331/64,117,176,177V,65,70 340/195,224
• US Class Current: 340/870.37
• CPC Class Codes: A61B 5/073 Intestinal transmitters
• CPC Class Codes: A61B 5/42 Detecting, measuring or recording for evaluating the gastrointestinal, the endocrine or the exocrine systems A61B1/00, A61B5/4857, A61B5/486, A61B5/4866, A61B5/4869 take precedence
• CPC Class Codes: H03B 2200/0008 Colpitts oscillator
• CPC Class Codes: H03B 2200/004 including a variable capacitance, e.g. a varicap, a varactor or a variable capacitance of a diode or transistor
• CPC Class Codes: H03B 2201/0208 the means being an element with a variable capacitance, e.g. capacitance diode
• CPC Class Codes: H03B 5/1203 the amplifier being a single transistor
• CPC Class Codes: H03B 5/1231 the amplifier comprising one or more bipolar transistors
• CPC Class Codes: H03B 5/1243 the means comprising voltage variable capacitance diodes

Abstract

This invention relates to a Colpitts oscillator circuit for a radio capsule of the type adapted to be swallowed by a patient for investigating a condition of the gastrointestinal tract. The circuit includes a transistor as the active element and a parallel resonant LC circuit including the series combination of a variable capacitance diode and first and second capacitors, the capacitance of the second capacitor being the larger of the two in order to provide the minimum amount of positive feedback required to cause stable oscillation. The capacitance of the first capacitor, which is connected between the diode and the transistor emitter, approximates that of the diode at the lowest voltage applied to the diode by a sensor device.

Claims

1. In a radio capsule adapted to be swallowed by a patient for investigating a condition of the gastro-intestinal tract, said capsule being of the type comprising:

a voltage source, a sensor for providing a voltage, the value of which is determined by said investigated condition, and an oscillator for generating an rf signal, the frequency of which is determined by said sensor voltage, said oscillator being characterized in that it comprises an active element having at least one input terminal and an output terminal, biasing means connecting said voltage source to said active element, a reference potential terminal, an inductor having a first terminal connected to said active element output terminal and a second terminal connected to said reference potential terminal, the series combination of a variable capacitance diode, a first capacitor and a second capacitor connected in the order named in parallel with said inductor, the capacitance of said second capacitor being larger than that of said first capacitor, said diode being connected to said first terminal of said inductor, first means connecting said sensor to the junction between said first capacitor and said diode, and second means connecting the junction between said first and second capacitors to said active element input terminal.

2. A radio capsule in accordance with claim 1 wherein the capacitance of said first capacitor is about equal to that of said diode at the lowest voltage provided by said sensor.

3. A radio capsule in accordance with claim 2 wherein said second connecting means is a resistor.

4. A radio capsule in accordance with claim 3 wherein said first connecting means is a resistor, the resistance of which is small compared to both the impedance of said diode and the impedance of said sensor.

5. A radio capsule in accordance with claim 4 wherein said active element is a transistor having emitter, base and collector electrodes, said collector electrode constituting said output terminal and said emitter electrode constituting said input terminal, the base of said transistor being connected to said reference potential terminal.

6. In a radio capsule adapted to be swallowed by a patient for investigating a condition of the gastro-intestinal tract, said capsule being of the type comprising:

a voltage source, a sensor for providing a voltage, the value of which is determined by said investigated condition, and an oscillator for generating an rf signal, the frequency of which is determined by said sensor voltage, said oscillator being characterized in that it comprises a transistor having base collector and emitter electrodes, biasing means connecting said voltage source to said emitter electrode, a reference potential terminal, said base electrode and a terminal of said voltage source being connected to said reference potential terminal, an inductor connected between said collector electrode and said reference potential terminal, the series combination of a variable capacitance diode, a first capacitor and a second capacitor connected in the order named in parallel with said inductor, the capacitance of said second capacitor being much larger than that of said first capacitor, the junction between said first and second capacitors being connected to said biasing means, said diode being connected to said collector electrode, and means connecting said sensor to the junction between said first capacitor and said diode.

7. A radio capsule in accordance with claim 6 wherein said biasing means comprises first and second resistors connected in series between said emitter electrode and said voltage source, the junction between said first and second resistors being directly connected to the junction between said first and second capacitors.

8. A radio capsule in accordance with claim 7 wherein the capacitance of said first capacitor is about equal to that of said diode at the lowest sensor voltage.

9. In a radio capsule adapted to be swallowed by a patient for investigating a condition of the gastro-intestinal tract, said capsule being of the type comprising:

a voltage source, a sensor for providing a voltage, the value of which is determined by said investigated condition, and an oscillAtor for generating an rf signal, the frequency of which is determined by sensor voltage, said oscillator being characterized in that it comprises a transistor having base, collector and emitter electrodes, first and second resistors connected between said emitter electrode and the first terminal of said voltage source, the second terminal of said source being connected to said base electrode, an inductor connected between said collector electrode and the second terminal of said source, the series combination of a variable capacitance diode, a first capacitor and a second capacitor connected in the order named in parallel with said inductor, the capacitance of said second capacitor being larger than that of said first capacitor, one terminal of said diode being connected to said collector electrode, the junction between said capacitors being connected to the junction between said first and second resistors, and means connecting said sensor to the junction between said first capacitor and said diode.

10. A radio capsule in accordance with claim 9 wherein a capacitance of said first capacitor approximates that of said diode at the lowest sensor voltage.