Multi-protocol radio frequency identification transponder tranceiver

• US 20060238301A1
• Filed: 06/16/2005
• Published: 10/26/2006
• Est. Priority Date: 02/22/2005
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Wu, Jiangfeng, Major, Donald Edward
• Granted Patent: US 7,689,195 B2
• Time in Patent Office: Days
• US Class Current: 340/10.100
• 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 5/0031 for data transfer
• CPC Class Codes: H04B 5/0062 in RFID [Radio Frequency Identification] Systems
• CPC Class Codes: H04B 5/72 for local intradevice communication
• CPC Class Codes: H04B 5/77 for interrogation

Abstract

A transceiver for a RFID reader and a transceiver for a RFID transponder (tag) allow communication between the two devices. The RFID reader utilizes an analog front end and a digital backend. In the receiver portion of the transceiver, the front end of the RFID reader uses a pair of down-conversion mixers to demodulate a received signal into in-phase (I) and quadrature (Q) components and analog-to-digital converters (ADC) digitize the signal. A digital signal processor (DSP) in the back end processes the digital signal and uses a matched filter for data detection. The RFID tag receives an inductively coupled signal from the reader and the receiver portion of the tag uses a pulse/level detector that employs an analog comparator and a sample and hold circuit to detect the received signal. A digital decoder/controller is used to decode the incoming data and to establish a sampling clock for the pulse/level detector. An automatic gain control (AGC) circuit adjusts a receiver gain according to the received signal strength and controls tuning of magnetic coupling circuitry.

Claims

1. An apparatus comprising:

a receiver to receive a radio frequency identification (RFID) signal, remove a carrier, extract an envelope of the RFID signal, compare the envelope to a previous envelope sample and generate an output for a digital decoder, the receiver also including an automatic gain control circuit to control gain of the receiver and tuning of an antenna circuit; and

a transmitter to modulate a RFID reply signal that is to be transmitted in response to receiving the RFID signal at the receiver.

2. The apparatus of claim 1 wherein the receiver and the transmitter are manufactured on a complementary metal-oxide semiconductor (CMOS) integrated circuit to operate at CMOS compatible voltages.

3. The apparatus of claim 2 wherein the tuning circuit and a modulation load for the transmitter are located off-chip of the CMOS integrated circuit due to a presence of voltages higher in magnitude than the CMOS compatible voltages.

4. The apparatus of claim 2 further including an attenuator at an input of the receiver to attenuate the received RFID signal to voltages compatible for the CMOS integrated circuit.

5. The apparatus of claim 4 wherein the attenuator is programmable to change an amount of attenuation of the received RFID signal.

6. The apparatus of claim 5 wherein the digital decoder is programmable to receive and process different RFID protocols.

7. A radio frequency identification (RFID) transponder receiver comprising:

a first detector to remove a carrier and extract an envelope of a received RFID signal;

a second detector, coupled to receive the extracted envelope of the received RFID signal, compare the extracted envelope with a previous envelope sample and generate an output in response to the comparison;

a digital decoder coupled to control an operation of the second detector and to calculate when the output is valid; and

an automatic gain control (AGC) circuit coupled to the first detector and the digital decoder to control a gain of the receiver.

8. The radio frequency identification (RFID) transponder receiver of claim 7 wherein the first detector is an envelope detector.

9. The radio frequency identification (RFID) transponder receiver of claim 8 wherein the second detector is a pulse/level detector which includes a sample and hold circuit and a comparator to detect a pulse or a level change of the extracted envelope and in which the digital decoder to send a sampling clock to the sample and hold circuit.

10. The radio frequency identification (RFID) transponder receiver of claim 9 wherein the comparator is a non-clocked hysteresis comparator.

11. The radio frequency identification (RFID) transponder receiver of claim 10 wherein the comparator has offset and hysteresis settings which are programmable.

12. The radio frequency identification (RFID) transponder receiver of claim 11 wherein the second detector also includes a programmable gain amplifier to amplify the extracted envelope.

13. The radio frequency identification (RFID) transponder receiver of claim 10 further including an attenuator at an input of the receiver to attenuate the received RFID signal to voltages compatible for input to the receiver.

14. The radio frequency identification (RFID) transponder receiver of claim 13 wherein the attenuator is programmable to change an amount of attenuation of the received RFID signal and the AGC circuit is to be used to control the attenuator.

15. The radio frequency identification (RFID) transponder receiver of claim 14 wherein the AGC circuit also changes a tuning of an input antenna circuit to adjust signal level of the received RFID.

16. A method comprising:

receiving an incoming radio frequency identification (RFID) signal at a receiver of a RFID transponder;

detecting the RFID signal to remove a carrier and extract an envelope of a received RFID signal;

detecting the extracted envelope of the received RFID signal by comparing the extracted envelope with a previous envelope sample to generate an output in response to the comparison;

calculating when the output is valid using a digital decoder; and

controlling gain applied to the received RFID signal by use of an automatic gain control (AGC) loop in response to the detected RFID signal strength.

17. The method of claim 16 wherein detecting the RFID signal includes performing envelope detection.

18. The method of claim 17 wherein detecting the extracted envelope includes performing a sample and hold for a previously extracted envelope sample and a comparison of the previous extracted envelope sample with a current extracted envelope to detect a pulse or a level change of the extracted envelope.

19. The method of claim 18 wherein the comparison includes programmably adjusting offset and hysteresis settings for the comparison.

20. The method of claim 19 wherein controlling the gain includes attenuating the received RFID signal at an input of the receiver to attenuate the received RFID signal to voltages suitable for input to the receiver.