Modulated tuned L/C transmitter circuits

• US 20070109819A1
• Filed: 11/17/2005
• Published: 05/17/2007
• Est. Priority Date: 11/17/2005
• Status: Abandoned Application

• Current Assignee: George Powell
• Original Assignee: George Powell
• Inventors: Powell, George
• Application Number:
  US11/281,338
• Publication Number:
  US 20070109819A1
• Time in Patent Office: Days
• US Class Current: 363/21.20
• CPC Class Codes: H03C 1/08 by means of variable impedance element H03C1/28 - H03C1/34, H03C1/46 - H03C1/52, H03C1/62 take precedence
• CPC Class Codes: H03C 3/145 by using semiconductor elements

Abstract

A transmitter circuit for generating a modulated oscillating output signal, comprises a tuned inductor-capacitor resonant circuit, and further comprise switching means for changing the resonant circuit capacitance by switching a capacitance into and out of circuit, wherein the resulting change in resonant circuit output is used to provide modulation of the output with a data signal. The invention thus interrupts the resonant cycling of a resonant oscillator circuit to provide a modulation function, and this is achieved by switching the (or one of many) capacitors into and out of circuit.

Claims

1. A transmitter circuit for generating a modulated oscillating output signal, comprising a tuned inductor-capacitor resonant circuit, and further comprising:

switching means for changing the resonant circuit capacitance by switching a capacitance into and out of circuit, wherein the resulting change in resonant circuit output is used to provide modulation of the output with a data signal.

2. A circuit as claimed in claim 1, wherein the tuned inductor-capacitor resonant circuit comprises an inductor and a capacitor in parallel.

3. A circuit as claimed in claim 2, wherein the tuned inductor-capacitor circuit further comprises a second capacitor in a third parallel branch.

4. A circuit as claimed in claim 1, wherein the tuned inductor-capacitor resonant circuit comprises an inductor and a capacitor in series.

5. A circuit as claimed in claim 2, wherein the switching means comprises an electronic switch in series with the capacitor.

6. A circuit as claimed in claim 5, further comprising timing control means for opening the electronic switch at a time within the cycle of the resonant circuit when substantially a maximum charge is stored on the capacitor.

7. A circuit as claimed in claim 5, further comprising timing control means for opening the electronic switch at a time within the cycle of the resonant circuit when substantially a minimum charge is stored on the capacitor.

8. A circuit as claimed in claim 5, wherein the switching means comprises a transistor, and a diode is provided between the source and drain of the transistor to allow current to flow in the reverse direction across the transistor.

9. A circuit as claimed in claim 1, further comprising a second switching means in series with a shorting diode, the second switching means and the shorting diode being in parallel with the tuned inductor-capacitor resonant circuit.

10. A radio frequency tag system comprising a transmitter having a circuit as claimed in claim 1, and a plurality of tags, each comprising receiving circuitry for receiving and demodulating the signal sent by the transmitter.

11. A method of providing amplitude modulation of a tuned inductor-capacitor resonant circuit, the method comprising:

switching the capacitor of the tuned inductor-capacitor resonant circuit out of circuit substantially at a point in time when maximum charge is stored on the capacitor to provide a modulation of a first amplitude; and

switching the capacitor of the tuned inductor-capacitor resonant circuit back in to circuit to provide a modulation of a second amplitude.

12. A method of providing frequency modulation of a tuned inductor-capacitor resonant circuit, the method comprising:

switching a capacitor of the tuned inductor-capacitor resonant circuit out of circuit substantially at a point in time when maximum energy is stored in the inductor to provide a modulation of a first frequency; and

switching the capacitor of the tuned inductor-capacitor resonant circuit back in to circuit at another point in the cycle time when maximum energy is again stored in the inductor to provide modulation of a second frequency.