RFID reader architecture

• US 7,664,461 B2
• Filed: 03/16/2006
• Issued: 02/16/2010
• Est. Priority Date: 03/02/2006
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Rofougaran, Ahmadreza (Reza), Shoarinejad, Kambiz
• Primary Examiner(s): Maung; Nay A
• Assistant Examiner(s): NGUYEN, TUAN HOANG
• Application Number:
  US11/377,812
• Publication Number:
  US 20070207732A1
• Time in Patent Office: 1,433 Days
• Field of Search: 455/11.1, 455/41.1, 455/41.2, 455/41.3, 455/73, 455/127.4, 455/552.1, 455/553.1, 340/10.1, 340/10.2, 340/10.3, 340/572.1, 375/295, 375/316
• US Class Current: 455/41.1
• 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
• CPC Class Codes: H04B 1/525 with means for reducing leakage of transmitter signal into the receiver

Abstract

A highly integrated and low-cost reader for a radio frequency identification (RFID) system is realized by providing a transmitter operable to generate an outbound radio frequency (RF) signal and a receiver operable to receive an inbound RF signal having a frequency similar to a frequency of the outbound RF signal on a single integrated circuit. Since the inbound RF signal may include not only a modulated RF signal produced by an RFID tag responsive to the outbound RF signal, but also a blocking signal corresponding to the outbound RF signal, the receiver additionally includes a block cancellation module operable to substantially cancel the blocking signal from the inbound RF signal using the outbound RF signal and to substantially pass the modulated RF signal before down-conversion of the modulated RF signal.

Claims

1. A reader for a radio frequency identification system, comprising:

a transmitter operable to generate an outbound radio frequency (RF) signal;

a receiver operable to receive an inbound RF signal having a frequency similar to a frequency of said outbound RF signal, said inbound RF signal including a blocking signal corresponding to said outbound RF signal and a modulated RF signal produced responsive to said outbound RF signal, said receiver comprising;

a low noise amplifier operably coupled to amplify said inbound RF signal to produce an amplified inbound RF signal,

a block cancellation module operably coupled to receive said outbound RF signal from said transmitter and to substantially cancel said blocking signal from said amplified inbound RF signal using said outbound RF signal and substantially pass said modulated RF signal, wherein said block cancellation module comprises;

a controller operably coupled to receive said outbound RF signal and to produce a cancellation signal from said outbound RF signal;

a carrier injection module operably coupled to receive said inbound RF signal and said cancellation signal and to substantially cancel said blocking signal and substantially pass said modulated RF signal using said cancellation signal; and

a feedback loop operably coupled to control said cancellation signal based on said modulated RF signal;

a down-conversion module operably coupled to convert said modulated RF signal to a near baseband signal, and

a digitizing module operably coupled to convert said near baseband signal into a digital baseband signal; and

a processing module operably coupled to convert said digital baseband signal into inbound digital symbols.

2. The reader of claim 1, wherein said reader is integrated on a single chip.

3. The reader of claim 1, wherein said transmitter comprises a first power amplifier operably coupled to amplify said outbound RF signal, and wherein said block cancellation module is operably coupled to receive said outbound RF signal from an output or an input of said first power amplifier, and further including:

an antenna operably coupled to receive said outbound RF signal and transmit said outbound RF signal.

4. The reader of claim 3, wherein said transmitter comprises a second power amplifier operably coupled to receive said outbound RF signal and produce an amplified outbound RF signal, and wherein said block cancellation module is operably coupled to receive said outbound RF signal from an input or an output of said second power amplifier, and further including:

a coil operably coupled to receive said amplified outbound RF signal and transmit said amplified outbound RF signal by generating and modulating the strength of a magnetic field.

5. The reader of claim 1, wherein said outbound RF signal is a modulated RF signal during a first time period and an unmodulated continuous wave RF signal during a second time period.

6. The reader of claim 1, wherein said reader is implemented in a CMOS integrated circuit, and wherein said transmitter further comprises:

multiple power amplifiers, each operably coupled to receive a respective partial outbound RF signal and to amplify said respective partial outbound RF signals to produce corresponding amplified partial outbound RF signals; and

a power controller operably coupled to control the power of each of said power amplifiers to within a limit of said CMOS integrated circuit.

7. The reader of claim 6, wherein said transmitter further comprises:

a combining load operably coupled to combine said amplified partial outbound RF signals to produce said outbound RF signal.

8. The reader of claim 6, wherein said transmitter further comprises:

an antenna away including multiple antennas, each operably coupled to receive a respective amplified partial outbound RF signal and to transmit said respective amplified partial outbound RF signal for combination of said amplified partial outbound RF signals over an air interface to produce said outbound RF signal.

9. The reader of claim 8, wherein said transmitter further comprises:

a phase distribution controller operably coupled to said power amplifiers to control a respective phase of each of said amplified partial outbound RF signals.

10. The reader of claim 8, wherein each of said multiple power amplifiers further comprises:

multiple power amplifiers, each operably coupled to receive a respective sub-partial outbound RF signal and to amplify said respective sub-partial outbound RF signals to produce corresponding amplified sub-partial outbound RF signals; and

a combining load operably coupled to combine said amplified sub-partial outbound RF signals to produce said respective amplified partial outbound RF signal.

11. The reader of claim 6, wherein said power amplifiers are non-linear, and wherein said power controller is further operable to modulate the power provided to each of said power amplifiers to produce an amplitude-modulated outbound RF signal.

12. The reader of claim 1, wherein said digitizing module is a limiter or an analog-to-digital converter.

13. The reader of claim 1, further comprising:

a host interface operably coupled to interface said reader with a host device.

14. The reader of claim 1, further comprising:

a frequency synthesizer operable to produce signals at multiple frequencies and operably coupled to said transmitter to generate said outbound RF signal at one of said multiple frequencies.

15. The reader of claim 1, wherein said processing module is programmed with multiple protocols, and wherein said processing module converts said digital baseband signal into said digital symbols using a select one of said protocols.

16. A method for operating an integrated reader for a radio frequency identification system, comprising:

generating an outbound radio frequency (RF) signal;

receiving an inbound RF signal having a frequency similar to a frequency of said outbound RF signal, said inbound RF signal including a blocking signal corresponding to said outbound RF signal and a modulated RF signal produced responsive to said outbound RF signal;

amplifying said inbound RF signal to produce an amplified inbound RF signal;

substantially cancelling said blocking signal from said amplified inbound RF signal by producing a cancellation signal from said outbound RF signal, substantially canceling said blocking signal and substantially passing said modulated RF signal using said cancellation signal and using a feedback loop to control said cancellation signal based on said modulated RF signal;

converting said modulated RF signal to a near baseband signal;

converting said near baseband signal into a digital baseband signal; and

converting said digital baseband signal into inbound digital symbols.

17. The method of claim 16, wherein said outbound RF signal is a modulated RF signal during a first time period and an unmodulated continuous wave RF signal during a second time period.

18. The method of claim 16, wherein said generating further comprises:

receiving partial outbound RF signals;

amplifying each of said respective partial outbound RF signals to produce corresponding amplified partial outbound RF signals; and

combining said amplified partial outbound RF signals to produce said outbound RF signal.

19. The method of claim 18, wherein said generating further comprises:

controlling a respective phase of each of said amplified partial outbound RF signals.

20. The reader of claim 16, wherein said generating further comprises:

modulating the power of each of said amplified partial outbound RF signals to produce an amplitude-modulated outbound RF signal.