Multi-transceiver RFID reader system with centralized control and frequency source

• US 8,174,363 B2
• Filed: 07/16/2008
• Issued: 05/08/2012
• Est. Priority Date: 07/16/2008
• Status: Expired due to Fees

• Current Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Original Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Inventors: Greene, John Clay
• Primary Examiner(s): Wu, Daniel
• Assistant Examiner(s): RUSHING, MARK S
• Application Number:
  US12/174,238
• Publication Number:
  US 20100013598A1
• Time in Patent Office: 1,392 Days
• Field of Search: 342/42, 342/44, 342/454, 340/572, 340/10
• US Class Current: 340/10.1
• 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

Embodiments of the present invention provide RFID systems having a centralized frequency source and controller. The centralized frequency source generates a reference signal, having a frequency below the RF band of interest, which is transmitted to a plurality of reader nodes. The centralized controller generates and transmits data to the plurality of reader nodes. At each reader node, the reference signal is converted to an RF carrier signal that is modulated and transmitted within corresponding read field of the reader node. This modulated RF carrier signal may interrogate and communicate with one or more RFID tags within this read field. The RF carrier signal may also be held constant to enable communication from RFID tags to the reader node, which is subsequently transmitted back to the centralized controller or processor.

Claims

1. An RFID system comprising:

a centralized frequency source that generates a reference signal having a frequency below an RF band of interest, the band of interest having an upper-frequency boundary and a lower frequency boundary;

a centralized controller that generates a data signal having information related to at least one RFID tag;

a reader node, coupled to receive the reference signal and the data signal, the reader node comprising;

a communication and synchronization module that applies a frequency multiplication operation on the reference signal to increase the frequency of the reference signal to generate an RF carrier signal and generates RFID tag commands from the data signal;

a transceiver, coupled to receive the RFID tag commands and RF carrier signal, the transceiver modulating the RF carrier signal with the RFID tag commands and transmitting the modulated RF carrier signal into a read field.

2. The system of claim 1 wherein the frequency multiplier module comprises a phase locked loop.

3. The system of claim 1 wherein the frequency multiplication operation applies an integer scalar to the frequency of the reference signal.

4. The system of claim 1 wherein the frequency multiplication operation applies a non-integer scalar to the frequency of the reference signal.

5. The system of claim 1 wherein the communication and synchronization module comprises:

a data processing module, coupled to receive digital data signal from the centralized controller, the data processing module packetizes the digital data signal into a plurality of RFID tag commands.

6. The system of claim 1 further comprising non-RF cabling that couples the centralized frequency source to the reader node.

7. The system of claim 1 wherein the reader node is within a plurality of reader nodes, each reader node within the plurality of reader nodes having a corresponding read field.

8. A method for generating a modulated RF carrier signal within an RFID system, the method comprising:

generating a reference signal having a frequency below an RF band of interest, the band of interest having an upper-frequency boundary and a lower frequency boundary;

transmitting the reference signal to a plurality of reader nodes within the RFID system;

increasing the frequency of the reference signal by applying a frequency multiplication operation to the reference signal resulting in an RF carrier signal, the frequency multiplication operation being performed on a first reader node within the plurality of reader nodes; and

modulating the RF carrier signal with data prior to transmission into a read field of the first reader node within the plurality of reader nodes.

9. The method of claim 8 wherein the frequency multiplication operation is performed by a phase-locked loop.

10. The method of claim 9 wherein the frequency multiplication operation applies an integer scalar to the frequency of the reference signal.

11. The method of claim 9 wherein the frequency multiplication operation applies a non-integer scalar to the frequency of the reference signal.

12. The method of claim 8 further comprising the step of:

combining the reference signal and at least one data signal on a bus between a centralized controller and a reader node.

13. The method of claim 8 wherein the step of transmitting the reference signal to the plurality of reader nodes is performed using non-RF cabling.

14. A communication and synchronization device in a reader node within an RFID system, the device comprising:

a data processing module, coupled to receive a digital data signal from a centralized controller, the data processing module formats information within the digital data signal for transmission into a read field of the reader node and outputs a formatted digital data signal; and

a frequency multiplier, coupled to receive a reference signal from the centralized controller having a frequency below an RF band of interest, the band of interest having an upper-frequency boundary and a lower frequency boundary, the frequency multiplier applies a frequency multiplication operation to the reference signal to increase the frequency of the reference signal to fall within the RF band of interest and outputs a corresponding RF carrier signal.

15. The communication and synchronization device of claim 14 comprising:

a first input on which the digital data signal is received and forwarded to the data processing module; and

a second input on which the reference signal is received and forwarded to the frequency multiplier.

16. The communication and synchronization device of claim 14 comprising:

a first output, coupled to the processing module, the first output transmits the formatted digital data signal to a transceiver;

a second output, coupled to the frequency multiplier, the second output transmits the RF carrier signal to the transceiver.

17. The communication and synchronization device of claim 16 wherein the RF carrier signal is modulated with the formatted digital data signal.

18. The communication and synchronization device of claim 14 wherein the frequency multiplication operation applies an integer scalar to the reference signal.

19. The communication and synchronization device of claim 14 wherein the frequency multiplication operation applies a non-integer scalar to the reference signal.