High efficiency RF amplifier and envelope modulator

• US 20070066224A1
• Filed: 02/27/2006
• Published: 03/22/2007
• Est. Priority Date: 02/28/2005
• Status: Abandoned Application

• Current Assignee: Sirit Technologies, Inc.
• Original Assignee: Sirit Corporation
• Inventors: Barink, Bernard, d'Hont, Loek
• Application Number:
  US11/362,984
• Publication Number:
  US 20070066224A1
• Time in Patent Office: Days
• US Class Current: 455/41.200
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer

Abstract

An RFID reader, comprising a high-efficiency Class-C power amplifier having an input, an output, and a supply voltage, a modulator coupled to the supply voltage of the Class-C power amplifier, and an RF carrier signal coupled to the input of the Class-C power amplifier. The modulator changes the supply voltage of the Class-C power amplifier resulting in highly controlled amplitude modulation of the RF carrier signal at the output of the Class-C power amplifier.

Claims

1. An RFID reader, comprising:

a Class-C power amplifier having an input, an output, and a supply voltage;

a modulator coupled to the supply voltage of the Class-C power amplifier; and

an RF carrier signal coupled to the input of the Class-C power amplifier;

wherein the modulator changes the supply voltage of the Class-C power amplifier resulting in highly controlled amplitude modulation of the RF carrier signal at the output of the Class-C power amplifier.

2. The RFID reader of claim 1, wherein the input of the Class-C power amplifier includes a high-Q tank circuit.

3. The RFID reader of claim 1, wherein the output of the Class-C power amplifier includes a high-Q tank circuit.

4. The RFID reader of claim 1, wherein the modulator is a transistor having an emitter-follower configuration.

5. The RFID reader of claim 4, wherein an information signal is provided at the base of the emitter-follower configuration, wherein the information signal shapes the RF carrier signal during modulation.

6. The RFID reader of claim 5, wherein a supply voltage signal is provided at the collector of the emitter-follower configuration, wherein the supply voltage signal determines an output power of the RFID reader.

7. The RFID reader of claim 1, wherein the modulator is a transistor having a source-follower configuration.

8. The RFID reader of claim 1, wherein a DC bias voltage is set by a digital or analog potentiometer in order to operate in Class-C mode.

9. The RFID reader of claim 1, further comprising an inverter at the input of the Class-C power amplifier for hard-switching a phase of the RF carrier signal between 0 and 180 degrees at the same time as performing amplitude modulation resulting in phase-reversal amplitude shift keying (PRASK) modulation at the output of the Class-C power amplifier.

10. The RFID reader of claim 1, wherein the Class-C power amplifier is suitable for use in Power over Ethernet (PoE) applications.

11. A method for use in an RFID reader, the method comprising:

providing an information signal for modulation;

providing an RF carrier signal to an input of a power amplifier;

setting a DC bias voltage so that the power amplifier is operating in Class-C mode; and

changing a supply voltage of the power amplifier with the information signal resulting in highly controlled amplitude modulation of the RF carrier signal at an output of the power amplifier.

12. The method of claim 11, further comprising inverting the carrier signal back and forth while at the same time performing amplitude modulation resulting in phase-reversal amplitude shift keying (PRASK) modulation at the output of the power amplifier.

13. The method of claim 11, further comprising tuning and impedance matching the input and output of the power amplifier with high-Q tank circuits.

14. The method of claim 11, wherein changing the supply voltage of the power amplifier includes configuring a transistor with an emitter-follower circuit and driving the transistor with the information signal.

15. The method of claim 14, further comprising providing a supply voltage signal to the collector of the emitter-follower circuit for setting a power output of the RFID reader.

16. The method of claim 11, further comprising pre-distorting the information signal so that the resulting amplitude modulation is a linear operation.

17. An RFID reader, comprising:

a transmitter having a Class-C power amplifier with an input, an output, a supply voltage;

a transistor having an emitter-follower configuration coupled to the supply voltage of the Class-C power amplifier;

an RF carrier signal generator coupled to the input of the amplifier; and

a digital signal processor or controller generating an information signal;

wherein the information signal drives the transistor resulting in highly controlled amplitude modulation at the output of the Class-C power amplifier.

18. The RFID reader of claim 17, wherein the input and output include high-Q tank circuits.

19. The RFID reader of claim 17, wherein the transmitter is suitable for use in Power over Ethernet (PoE) applications.

20. The RFID reader of claim 17, wherein the digital signal processor or controller generates a supply voltage signal that is coupled to the collector of the emitter-follower configuration, wherein the supply voltage signal allows the digital signal processor to set a power setting for the RFID reader.