RFID antenna system having reduced orientation sensitivity

• US 20070194929A1
• Filed: 02/17/2006
• Published: 08/23/2007
• Est. Priority Date: 02/25/2005
• Status: Active Grant

• Current Assignee: Datalogic Mobile Incorporated (Datalogic S.p.A.)
• Original Assignee: PSC Scanning, Inc. (Datalogic ADC Incorporated)
• Inventors: McAllister, Clarke, Wagner, James, Cohen, Mark
• Granted Patent: US 7,515,051 B2
• Time in Patent Office: Days
• US Class Current: 340/572.7
• CPC Class Codes: G06K 7/10346 the antenna being of the far field type, e.g. HF types or dipoles
• CPC Class Codes: H01Q 1/2216 used in interrogator/reader equipment
• CPC Class Codes: H01Q 21/24 Combinations of antenna units polarised in different directions for transmitting or receiving circularly and elliptically polarised waves or waves linearly polarised in any direction circularly polarised patch antennas H01Q9/0428; circularly polarised horns H01Q13/0241; cross-polarised horns H01Q13/0258; polarisation converters H01Q15/242; cross-polarised rear feeds H01Q19/136; crossed polarisation dual antenna H01Q25/001
• CPC Class Codes: H01Q 3/24 varying the orientation by switching energy from one active radiating element to another, e.g. for beam switching

Abstract

Radio Frequency Identification (RFID) antennas systems and methods that are less sensitive to orientation. One example includes an interrogator having a radio frequency transceiver, a first linearly polarized antenna in electrical communication with the transceiver, and a second linearly polarized antenna in electrical communication with the transceiver, the second antenna having a polarization in a direction substantially perpendicular to the first antenna; a control circuit is in electrical communication with the transceiver and with the first and second antennas, the control circuit operable to switch between interrogating with the first antenna and interrogating with the second antenna, and an RFID decoder is coupled to an output of the transceiver to decode an interrogated electromagnetic signal from a tag.

Claims

1. A tag reader comprising:

a plurality of linearly polarized antennas, including at least a first antenna and a second antenna arranged non-parallel to the first antenna;

a control circuit in electrical communication with the plurality of antennas, the control circuit operable to switch the plurality of antennas on and off, wherein the first and second antennas transmit at different times; and

circuitry coupled to an output of the plurality of antennas to receive an electromagnetic signal from a tag in response to a transmission from one of the plurality of antennas.

2. A tag reader according to claim 1, wherein the control circuit comprises a microprocessor.

3. A tag reader according to claim 1, wherein at least one of the plurality of antennas is a patch antenna.

4. A tag reader according to claim 1, wherein the control circuit switches the plurality of antennas on and off sequentially.

5. A tag reader according to claim 1, wherein at least one of the plurality of antennas is an antenna array.

6. A tag reader according to claim 1, further comprising an optical code reader comprising:

a photosensitive detector;

an optical collector for directing light reflected from a bar code onto the photosensitive detector;

circuitry coupled to the photosensitive detector to process the detected light; and

a decoder to decode the processed detected light.

7. An RFID interrogator comprising:

a radio frequency transceiver;

a first linearly polarized antenna in electrical communication with the transceiver;

a second linearly polarized antenna in electrical communication with the transceiver, the second antenna having a polarization in a direction substantially perpendicular to the first antenna;

a control circuit in electrical communication with the transceiver and with the first and second antennas, the control circuit operable to switch between interrogating with the first antenna and interrogating with the second antenna; and

an RFID decoder coupled to an output of the transceiver to decode an interrogated electromagnetic signal from a tag.

8. An interrogator according to claim 7, wherein the control circuit is user-controlled.

9. An interrogator according to claim 7, wherein the control circuit comprises a microprocessor.

10. An interrogator according to claim 7, wherein the first antenna is horizontally polarized, and the second antenna is vertically polarized.

11. An interrogator according to claim 7, wherein the first and second polarized antennas are each patch antennas.

12. An interrogator according to claim 7, wherein the first antenna comprises two polarized antennas, including one to interrogate for the electromagnetic signal and one to receive the interrogated electromagnetic signal.

13. An interrogator according to claim 7, wherein the second antenna comprises two polarized antennas, including one to interrogate for the electromagnetic signal and one to receive the interrogated electromagnetic signal.

14. An interrogator according to claim 7, wherein each of the first antenna and the second antenna each comprises an antenna array.

15. An interrogator according to claim 7, further comprising an optical code reader comprising:

a photosensitive detector;

an optical collector for directing light onto the photosensitive detector to receive a return optical signal from a bar code;

circuitry coupled to the photosensitive detector to process the return optical signal and to digitize the processed optical signal; and

a decoder to convert the digitized signal into an identification code.

16. An interrogator according to claim 15, further comprising:

a communications unit in electrical communication with the optical code reader and the electromagnetic tag reader; and

a computer bus coupled to the communications unit to send the decoded electromagnetic signal from the tag and the decoded identification code from the bar code to a computer.

17. An interrogator according to claim 16, wherein the communications unit and the computer are integrated within the interrogator.

18. A data reader comprising:

an RFID tag reader comprising;

a plurality of linearly polarized antennas, at least a first antenna and a second antenna arranged non-parallel to the first antenna;

a control circuit in electrical communication with the plurality of antennas, the control circuit operable to switch the plurality of antennas on and off, wherein the first and second antennas transmit at different times;

circuitry coupled to an output of the plurality of antennas to receive an electromagnetic signal from a tag in response to a transmission from one of the plurality of antennas; and

an RFID decoder coupled to an output of the circuitry to extract the tag'"'"'s identification from the received electromagnetic signal; and

an optical code reader comprising;

an optical light source to reflect light off a bar code;

a photosensitive detector to receive a return optical signal from the bar code;

circuitry coupled to the photosensitive detector to process the return optical signal and to digitize the processed signal; and

an optical decoder to decode the digitized signal to extract the bar code'"'"'s identification therefrom.

19. A data reader according to claim 18, further comprising a computer bus in electrical communication with the optical and the RFID decoders to send the extracted tag and bar code identifications to a computer.

20. A data reader according to claim 19, further comprising a communications unit in electrical communication with the RFID tag reader and with the optical code reader, the communications unit coupled to the computer bus.

21. A data reader according to claim 20, further comprising a user interface in electrical communication with the communications unit to enable a user to configure and control the multi-technology reader.

22. A data reader according to claim 20, wherein the communications unit and the computer are integrated within the data reader.

23. A method for identification tag interrogation, the method comprising:

alternately transmitting electromagnetic signals from a plurality of non-parallel, linearly polarized antennas, wherein less than all antennas transmit at the same time;

receiving a return electromagnetic signal including the identification of a tag in response to a transmission from one or more of the plurality of antennas; and

processing the return electromagnetic signal to extract the tag'"'"'s identification.

24. A method according to claim 23, the method further comprising switching sequentially in the alternate transmission of the plurality of antennas.

25. A method according to claim 24, wherein only one of the plurality of antennas transmits at any given time.

26. A computer readable medium having stored thereon computer executable instructions for performing or causing to be performed the method of claim 23.

27. A method for identification tag interrogation, the method comprising:

transmitting a first electromagnetic signal with a first linearly polarized antenna;

transmitting a second electromagnetic signal with a second linearly polarized antenna before or after the transmission of the first electromagnetic signal, the second antenna having a polarization in a direction not appreciably parallel to the first antenna;

receiving a return electromagnetic signal including the identification of a tag in response to a transmission from one of the first and second antennas; and

processing the return electromagnetic signal to extract the tag'"'"'s identification.

28. A method according to claim 27, wherein the second antenna is polarized in a direction substantially perpendicular to the first antenna.

29. A method according to claim 27, the method further comprising switching sequentially between transmitting with the first antenna and transmitting with the second antenna.

30. A method according to claim 27, wherein the first antenna is horizontally polarized, and the second antenna is vertically polarized.

31. A method according to claim 27, wherein the first antenna comprises two polarized antennas, including one to transmit the first electromagnetic signal and one to receive the return electromagnetic signal.

32. A method according to claim 27, wherein the second antenna comprises two polarized antennas, including one to transmit the second electromagnetic signal and one to receive the return electromagnetic signal.

33. A computer readable medium having stored thereon computer executable instructions for performing or causing to be performed the method of 27.