Systems and methods for amplifying a transmit signal in a RFID interrogator

• US 7,054,595 B2
• Filed: 09/08/2003
• Issued: 05/30/2006
• Est. Priority Date: 09/08/2003
• Status: Active Grant

• Current Assignee: Smartrac Technology Fletcher, Inc. (Avery Dennison Corporation)
• Original Assignee: Single Chip Systems Corporation (OEP Technologie BV)
• Inventors: Bann, Gary
• Primary Examiner(s): To, Doris H.
• Assistant Examiner(s): WEST, LEWIS G
• Application Number:
  US10/658,633
• Publication Number:
  US 20050054293A1
• Time in Patent Office: 995 Days
• Field of Search: 455/41.2, 455/41.3, 455/41.1, 455/78, 455/73, 455/456.2, 340/10.1, 340/10.32, 340/10.42
• US Class Current: 455/41.2
• CPC Class Codes: G01S 13/751 wherein the responder or reflector radiates a coded signal
• 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
• CPC Class Codes: H01Q 1/2216 used in interrogator/reader equipment
• CPC Class Codes: H01Q 3/24 varying the orientation by switching energy from one active radiating element to another, e.g. for beam switching
• CPC Class Codes: H04W 52/52 using AGC [Automatic Gain Control] circuits or amplifiers

Abstract

An RFID interrogator comprises an amplifier configured to amplify signals being transmitted by the RFID interrogator. The RFID interrogator also comprises a bypass path to direct received signals around the amplifier so that the amplifier does no block the reception of signals received from an RFID tag.

Claims

1. An RFID interrogator, comprising:

an antenna configured to transmit and receive RF signals;

an RF transceiver configured to receive backscatter modulated RF signals, and generate transmit RF signals;

an amplifier coupled with the antenna the antenna and the RF transceiver configured to amplify the transmit RF signals;

a first energy director coupled between the RF transceiver and the amplifier, the first energy director configured to receive the RF transmit signal and direct thorn to the amplifier and to receive backscatter modulated RF signals and direct them to RF transceiver; and

a second energy director coupled between the amplifier and the antenna, the second energy director configured to receive the amplified transmit signals from to amplifier and send the amplified transmit signals to the antenna, and to receive a backscatter modulated RF signal from the antenna and direct the receive backscatter modulated RF signal to the first energy director bypassing the amplifier.

2. The RFID interrogator of claim 1, wherein the antenna transmits signals to, and receives signals from, an RFID tag.

3. The RFID interrogator of claim 1, wherein the directors are circulators.

4. The RFID interrogator of claim 1, wherein the directors are directional couplers.

5. The RFID interrogator of claim 1, wherein the amplifier is a variable gain amplifier (VGA).

6. The RFID interrogator of claim 1, further comprising a feedback loop coupled with the output of the amplifier, the feedback loop configured to sense the output energy from the amplifier and control the amplifier gain in response to the sensed output energy.

7. The RFID interrogator of claim 6, wherein the feedback loop maintains the transmit signal energy at or below a certain level.

8. The RFID interrogator of claim 6, wherein the feedback loop maintains the transmit signal energy at or above a certain level.

9. The RFID interrogator of claim 6, wherein the feedback loop includes an energy coupler, a rectifier, and a power leveling network.

10. The RFID interrogator of claim 1, further comprising a decoder coupled with the RF transceiver, and, wherein the RF transceiver is configured to send the received RF backscatter modulated signals to the decoder.

11. The RFID interrogator of claim 1, further comprising a switch and a plurality of antennas, and wherein the energy director is coupled with the switch, the switch configured to direct the transmit signal to one of the plurality of antennas.

12. The RFID interrogator of claim 11, further comprising a plurality of switches and wherein the energy director is coupled with the plurality of switches, each of the plurality of switches configured to direct the transmit signal to one or more of the plurality of antennas.

13. The RFID interrogator of claim 1, wherein the transmit signal is transmitted to a RFID tag.

14. The RFID scanner of claim 1, wherein the received signal contains data from the RFID tag.