Multi-protocol radio frequency identification transponder tranceiver

• US 7,689,195 B2
• Filed: 06/16/2005
• Issued: 03/30/2010
• 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
• Primary Examiner(s): Urban; Edward
• Assistant Examiner(s): HU, RUI MENG
• Application Number:
  US11/154,383
• Publication Number:
  US 20060238301A1
• Time in Patent Office: 1,748 Days
• Field of Search: 340 101- 1052, 3405721-5729, 340/551, 455/338, 455/336, 455/215, 455/339, 333/109, 323/220, 342/195, 342/51, 380/28
• US Class Current: 455/336
• 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. A passive radio frequency identification (RFID) transponder receiver that is powered by an induced magnetic field comprising:

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

a second detector includes a sample and hold circuit and a comparator, coupled to receive the extracted envelope of the received RFID signal, wherein the sample and hold circuit outputs a previous extracted envelope sample of the received RFID signal to an input of the comparator and the comparator compares a sample of the extracted envelope with the previous extracted envelope sample of the received RFID signal to generate an output in response to the comparison, in which the second detector samples a pulse of one polarity and inhibits sampling of a pulse of opposite polarity when operating in a pulse detection mode and detects level change of the extracted envelope when operating in a level detection mode;

a clock extractor to extract a clock signal from the received RFID signal;

a digital decoder coupled to the second detector and to the clock extractor to use the extracted clock signal from the clock extractor to generate a divided clock signal of reduced duty cycle from the extracted clock signal to clock the sample and hold circuit and in which the digital decoder determines when the extracted envelope meets a minimum threshold level in order for the output to be valid; and

an automatic gain control (AGC) circuit coupled to the first detector and the digital decoder to control a gain of an input attenuator circuit of the receiver to control input signal level of the received RFID signal to reside between an upper threshold level and a lower threshold level.

2. The radio frequency identification (RFID) transponder receiver of claim 1 wherein the first detector is an envelope detector.

3. The radio frequency identification (RFID) transponder receiver of claim 2 wherein the comparator is a non-clocked hysteresis comparator.

4. The radio frequency identification (RFID) transponder receiver of claim 3 wherein the comparator has offset and hysteresis settings which are programmable.

5. The radio frequency identification (RFID) transponder receiver of claim 4 wherein the second detector also includes a programmable gain amplifier to amplify the extracted envelope.

6. The radio frequency identification (RFID) transponder receiver of claim 3 wherein the AGC circuit is programmable to change the upper and lower threshold levels.

7. A method comprising:

receiving an incoming radio frequency identification (RFID) signal at a receiver of a RFID transponder, in which the RFID transponder is a passive transponder that is powered by an induced magnetic field from the received RFID signal;

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

detecting the extracted envelope of the received RFID signal by use of a sample and hold circuit to output a previous extracted envelope sample of the received RFID signal to an input of a comparator and by use of the comparator to compare a sample of the extracted envelope with the previous extracted envelope sample of the received RFID signal to generate an output in response to the comparison, in which the detecting of the extracted envelope includes sampling a pulse of one polarity and inhibiting sampling of a pulse of opposite polarity when operating in a pulse detection mode and detecting level change of the extracted envelope when operating in a level detection mode;

extracting a clock signal from the received RFID signal;

generating in a digital decoder, a divided clock signal of reduced duty cycle from the extracted clock signal to clock the sample and hold circuit;

determining in the digital decoder, when the extracted envelope meets a minimum threshold level in order for the output to be valid; and

controlling gain applied to the received RFID signal at an input attenuator by use of an automatic gain control (AGC) loop to control input signal level of the received RFID signal to reside between an upper threshold level and a lower threshold level.

8. The method of claim 7 wherein detecting the RFID signal includes performing envelope detection.

9. The method of claim 8 wherein the comparison includes programmably adjusting offset and hysteresis settings for the comparison.

10. The method of claim 8 wherein the upper and lower threshold levels are programmable.