Method and system for radiated power control for short range RFID tag reading

• US 8,159,331 B2
• Filed: 07/17/2007
• Issued: 04/17/2012
• Est. Priority Date: 07/17/2007
• Status: Active Grant

• Current Assignee: Psion PLC (Motorola Solutions, Inc.)
• Original Assignee: Psion Teklogix (Motorola Solutions, Inc.)
• Inventors: Stagg, Adrian Joseph
• Primary Examiner(s): Mehmood, Jennifer
• Assistant Examiner(s): BEE, ANDREW W.
• Application Number:
  US11/779,129
• Publication Number:
  US 20090021374A1
• Time in Patent Office: 1,736 Days
• Field of Search: 340 101- 1052, 3405721-5729
• US Class Current: 340/10.3
• CPC Class Codes: G06K 19/0701 at least one of the integrated circuit chips comprising an arrangement for power management
• CPC Class Codes: G06K 19/0715 the arrangement including means to regulate power transfer to the integrated circuit
• 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 method and system for power control for Radio Frequency Identification (RFID) tag reading is provided. The system includes a power amplifier for providing an RF transmit signal for the RFID tag reading. The RF transmit signal is provided to an antenna for radiating the transmit signal. The power of the radiated transmit signal defining a read range for the RFID tag reading. The system includes an attenuator provided between the power amplifier and the antenna for controlling the power of the radiated transmit signal to adjust the read range. A handheld RFID reader may include the system. The method includes calibrating the output power of a reader having a power amplifier and an attenuator provided between the power amplifier and an antenna. The step of calibrating includes at least one of controlling power of the power amplifier in its linear region, and controlling attenuation level of the attenuator.

Claims

1. A system for power control for Radio Frequency Identification (RFID) tag reading, comprising:

a power amplifier for providing an RF transmit signal for the RFID tag reading;

an attenuator for attenuating the RF transmit signal output from the power amplifier, an attenuated transmit signal from the attenuator being provided to an antenna; and

a controller for controlling each of the power amplifier and the attenuator, the controller operating the power amplifier within a linear operation region of the power amplifier, independent of the operation of the attenuator,

the attenuator being capable of reducing a field of view for the RFID tag reading to a greater extent than is possible by setting the power of the power amplifier to a minimum level in the linear operation region.

2. A system as claimed in claim 1, wherein the controller comprises:

a calibration module for calibrating at least one of a power setting of the power amplifier, an attenuation level of the attenuator or a combination thereof to singulate an RFID tag of interest among a plurality of RFID tags.

3. A system as claimed in claim 2, further comprising a memory for storing one or more calibrated settings for at least one of the power amplifier and the attenuator, which is obtained by the calibration module, each of the at least one of the calibrated settings being selectively enabled.

4. A system as claimed in claim 2, wherein one or more calibrated settings comprise:

a maximum power setting for singulating the RFID tag of interest, and

a minimum power setting that is obtained by further reducing the field of view for the RFID to reading after the RFID to of interest is singulated, until no tag is readable.

5. A system as claimed in claim 1, wherein the system comprises:

a radio module including;

an RF section having the power amplifier; and

the controller,

the controller being for communicating with a host and communicating with the RF section.

6. A system as claimed in claim 5, wherein the controller communicates with the host through a bi-directional link and decodes a command from the host.

7. A system as claimed in claim 6, wherein a voltage control of the power amplifier is written into a register based on the command from the host.

8. A system as claimed in claim 5, wherein the controller generates a control signal for controlling the attenuator.

9. A system as claimed in claim 5, wherein the attenuator is powered by the radio module or the host.

10. A system as claimed in claim 5, further comprising:

a radio interface for operably connecting the radio module and the host.

11. A system as claimed in claim 5, wherein the host is a handheld host terminal for the RFID tag reading.

12. A system as claimed in claim 5, wherein the RF transmit signal is connected between the radio module and the attenuator with an RF connection having a coax cable.

13. A system as claimed in claim 5, wherein the radio module provides at least one of power and a control signal to the attenuator via a flexible circuit.

14. A system as claimed in claim 5, wherein the system comprises:

a transmit path including the power amplifier and the attenuator; and

a receive path for receiving a response from one or more RFID tags.

15. A system as claimed in claim 1, wherein a host controls an output level of the power amplifier.

16. A system as claimed in claim 1, further comprising:

a host for controlling the power amplifier, the attenuator or a combination thereof for the RFID tag reading.

17. A handheld device comprising:

an RFID reader including an analog RF section having a power amplifier for providing an RF transmit signal for the RFID tag reading;

an antenna; and

an external attenuator, for attenuating the RF transmit signal output from the power amplifier, connected to the analog RF section and the antenna,

the RF reader including a controller for controlling the power amplifier and the attenuator, the controller operating the power amplifier in a linear operation region of the power amplifier, independent of the operation of the attenuator, the attenuator being capable of reducing a field of view for the RFID reader to a greater extent than is possible by setting the power of the power amplifier to a minimum level in the linear operation region.

18. A handheld device as claimed in claim 17, wherein the host comprises:

a user interface for operating the reader for the RFID tag reading.

19. A handheld device as claimed in claim 17, wherein the host comprises:

a module for calibrating the power of the radiated transmit signal to read a single RFID tag.

20. A method for power control for Radio Frequency Identification (RFID) tag reading, comprising:

setting a field of view of a handheld reader, the handheld reader including a power amplifier for providing an RF transmit signal for the RFID tag reading, and an attenuator for attenuating the RF transmit signal output from the power amplifier, an attenuated transmit signal from the attenuator being provided to an antenna;

controlling the power amplifier, including;

operating the power amplifier in a linear operation region of the power amplifier, independent of the operation of the attenuator; and

controlling an attenuation level of the attenuator, including;

enabling the attenuator to reduce a field of view for the RFID rag reading to a greater extent than is possible by setting the power of the power amplifier to a minimum level in the linear operation region.

21. A method as claimed in claim 20, comprising:

determining whether a RFID tag of interest is readable among a plurality of RFID tags.

22. A method as claimed in claim 20, comprising:

selectively retrieving a setting for at least one of the power amplifier and the attenuator to singualte an RFID to of interest.

23. A method as claimed in claim 20, wherein the step of setting comprises:

initially setting a power of the power amplifier to the maximum level in the linear operation region, and

the step of controlling the power amplifier, comprising;

decreasing the power of the power amplifier within the linear operation region.

24. A method as claimed in claim 20, the steps of controlling determines:

a first setting for the power amplifier and the attenuator at which the RFID tag of interest is singulated; and

a second setting for the power amplifier and the attenuator at which no tag is readable, the second setting being obtained by reducing the field of view after the RFID tag of interest is singulated.