Radio frequency ID Doppler motion detector

• US 20080061976A1
• Filed: 09/01/2006
• Published: 03/13/2008
• Est. Priority Date: 09/01/2006
• Status: Active Grant

• Current Assignee: Sensormatic Electronics LLC (Johnson Controls International plc)
• Original Assignee: Sensormatic Electronics Corporation (Johnson Controls International plc)
• Inventors: Shafer, Gary Mark
• Granted Patent: US 7,609,163 B2
• Time in Patent Office: Days
• US Class Current: 340/572.1
• CPC Class Codes: G01S 13/56 for presence detection presence detection using near field arrangements G01V3/00, e.g. G01V3/08, G01V3/12; burglar, theft or intruder alarms with electrical actuation G08B13/22 - G08B13/26
• CPC Class Codes: G01S 13/825 with exchange of information between interrogator and responder
• CPC Class Codes: G01S 7/023 Interference mitigation, e.g. reducing or avoiding non-intentional interference with other HF-transmitters, base station transmitters for mobile communication or other radar systems, e.g. using electro-magnetic interference [EMI] reduction techniques auxiliary means for detecting or identifying radar signals or the like G01S7/021; means for anti-jamming G01S7/36
• CPC Class Codes: G01S 7/352 Receivers
• 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

A system and method for a radio frequency identification (RFID) reader for use in an RFID detection system. The reader has an RF source for generating RF signals. An antenna is coupled to the RF source. The antenna transmits interrogation RF signals to one or more RFID markers within an interrogation zone and receives communication signals from one or more items within the interrogation zone. The communication signals include Doppler signals indicating movement of an item within the interrogation zone. A receiver receives the communication signals and motion detection circuitry detects the Doppler signals.

Claims

1. A radio frequency identification (RFID) reader for use in an RFID detection system, the reader comprising:

an RF source for generating RF signals;

an antenna coupled to the RF source, the antenna transmitting interrogation RF signals to one or more RFID markers within an interrogation zone and receiving communication signals from one or more items within the interrogation zone, wherein the communication signals include Doppler signals indicating movement of an item within the interrogation zone;

a receiver for receiving the communication signals; and

motion detection circuitry for detecting the Doppler signals.

2. The reader of claim 1, wherein the motion detection circuitry extracts the Doppler signals from the communication signals.

3. The reader of claim 1, wherein the motion detection circuitry comprises a directional coupler.

4. The reader of claim 1, further comprising a signal processor, wherein the motion detection circuitry is adapted to forward the Doppler signals to the signal processor.

5. The reader of claim 4, wherein the signal processor determines the relative speed of the item with respect to the reader.

6. The reader of claim 1, wherein the antenna transmits at a first power level to detect movement within the interrogation zone and transmits at a second power level greater than the first power level to detect the presence of an RFID marker within the interrogation zone if movement is detected.

7. The reader of claim 4, wherein the signal processor instructs the antenna to increase power transmitted to the one or more RFID markers if the item is indicated as being in motion.

8. An RFID detection system comprising:

one or more RFID markers; and

an RFID reader comprising;

an RF source for generating RF signals;

an antenna coupled to the RF source, the antenna transmitting interrogation signals to the one or more RFID markers within an interrogation zone and receiving communication signals from an item within the interrogation zone, wherein the communication signals include Doppler signals indicating movement of the item within the interrogation zone; and

a receiver for receiving the communication signals; and

motion detection circuitry for detecting the Doppler signals.

9. The RFID detection system of claim 8, further comprising a signal processor, wherein the signal processor receives the Doppler signals from the motion detection circuitry and determines movement of the item with respect to the reader.

10. The RFID detection system of claim 8, wherein the antenna transmits at a first power level to detect movement within the interrogation zone and transmits at a second power level greater than the first power level to detect the presence of an RFID marker within the interrogation zone if movement is detected.

11. The RFID detection system of claim 9, wherein the signal processor instructs the antenna to increase power transmitted to the one or more RFID markers if the signal processor determines that the item is in motion.

12. The RFID detection system of claim 8, wherein the motion detection circuitry resides within the RFID reader.

13. The RFID detection system of claim 8, wherein the motion detection circuitry is situated external to, but in communication with, the RFID reader.

14. The RFID detection system of claim 8, wherein the motion detection circuitry comprises a directional coupler.

15. A method of operating an RFID marker reader, the method comprising:

transmitting an interrogation signal at a first power level to detect movement of an item within the interrogation zone; and

transmitting the interrogation signal at a second power level greater than the first power level to detect the presence of a marker if movement of an item is detected within the interrogation zone.

16. The method of claim 15, further comprising detecting Doppler signals, the Doppler signals being evaluated to determine movement within the interrogation zone.

17. The method of claim 16, wherein movement is determined by evaluating the Doppler signals, the Doppler signals being evaluated by motion detection circuitry included as part of the RFID reader.

18. The method of claim 17, further comprising determining the relative speed of a moving item with respect to the RFID reader.

19. The method of claim 15, further comprising receiving a communication signal in response to interrogation signal transmitted at the second power level, the communication signal indicating the presence of a marker within the interrogation zone.

20. The method of claim 19, wherein the communication signal received response to interrogation signal transmitted at the second power level includes a Doppler signal indicating movement of the item within the interrogation zone, the Doppler signal being filtered out to determine the presence of a marker within the interrogation zone.