System for identifying radio-frequency identification devices

• US 7,639,137 B2
• Filed: 08/28/2006
• Issued: 12/29/2009
• Est. Priority Date: 08/30/2005
• Status: Expired due to Fees

• Current Assignee: Somnath Mukherjee
• Original Assignee: Somnath Mukherjee
• Inventors: Mukherjee, Somnath
• Primary Examiner(s): Nguyen; Tai T
• Application Number:
  US11/511,594
• Publication Number:
  US 20070046433A1
• Time in Patent Office: 1,219 Days
• Field of Search: 340/572.1, 340/572.4, 340/572.7, 340/10.1, 340/10.34, 340/10.4, 455/103, 455/104, 455/106, 342/42, 342/47, 342/51, 342/104, 342/114
• US Class Current: 340/572.1
• CPC Class Codes: G06K 19/0672 with resonating marks
• 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 system for identifying radio-frequency identification (RFID) devices is described. In one embodiment, RFID devices include an antenna and metallic pattern printed on a substrate. A probing platform is used to radiate the RFID devices with an electromagnetic signal (e.g., radio-frequency signal, microwave signal, etc.). Each RFID device generates a quantifiable backscatter depending on the unique impedance of the passive RFID device in response to the electromagnetic signal. The backscatter is employed to uniquely identify the passive RFID device'"'"'s impendence with respect to the probing platform uniquely characterized at predetermined frequencies of the electromagnetic signal.

Claims

1. A method of identifying a radio-frequency identification device, the method comprising:

transmitting a wireless signal that varies over a predetermined range of frequencies to a radio-frequency identification device having a predetermined impedance; and

processing backscatter wireless signals reflected from the radio-frequency identification device according to the radio-frequency identification device'"'"'s predetermined impedance to determine a device signature, wherein the processing comprises;

mixing the backscatter wireless signals with the transmitted wireless signal to form an intermediate frequency (IF) signal;

demodulating the IF signal to recover modulation information, the modulation information having a frequency response characteristic of a complex impedance, the radio-frequency identification device'"'"'s predetermined impedance having the complex impedance; and

using the modulation information to determine the device signature.

2. The method of claim 1, wherein the wireless signal is swept over the predetermined range.

3. The method of claim 1, wherein transmitting the wireless signal comprises directing a signal in a beam toward the radio-frequency identification device.

4. The method of claim 1, wherein the device signature is associated with a frequency dependent phase shift of the backscatter wireless signals associated with the impedance.

5. The method of claim 1, further comprising performing range gating such that the radio-frequency identification device is distinguished from another radio-frequency identification device at a different location.

6. A method of distinguishing a radio-frequency identification device from a group of radio-frequency identification devices, the method comprising:

transmitting a wireless signal that varies over a predetermined range of frequencies to a plurality of radio-frequency identification devices, wherein at least one radio-frequency identification device of the plurality of radio-frequency identification devices includes a predetermined reflective impedance configured to reflect at least a portion of the wireless signal with a predetermined reflection pattern; and

determining a unique device signature associated with the predetermined reflective impedance from wireless signals backscattered from the at least one radio-frequency identification device in response to the transmitted wireless signal, wherein the determining comprises;

mixing the backscatter wireless signals with the transmitted wireless signal to form an intermediate frequency (IF) signal;

demodulating the IF signal to recover modulation information, the modulation information having a frequency response characteristic of a complex impedance, the at least one radio-frequency identification device predetermined reflective impedance having the complex impedance; and

using the modulation information to determine the unique device signature.

7. The method of claim 6, wherein at least two of the plurality of radio-frequency identification devices comprise a unique predetermined reflective impedance with respect to the plurality of radio-frequency identification devices.

8. The method of claim 6, wherein transmitting the wireless signal comprises sweeping the wireless signal over the predetermined range of frequencies at a predetermined sweep rate that is sufficient to provide a received signal at a probing platform responsive to a delay time between the transmitted signal and a received portion of the backscattered wireless signal.

9. The method of claim 6, wherein one or more of the plurality of radio-frequency identification devices are formed using a printing process.

10. A radio-frequency (RF) identification device system, the system comprising:

a transmitter configured to transmit a wireless signal over a predetermined frequency range;

at least one radio-frequency identification device configured to reflect and scatter at least a portion of the transmitted wireless signal in a pattern associated with the predetermined impedance of the at least one radio-frequency identification device; and

a receiver configured to process an RF backscatter of the portion of the wireless signal received from the at least one radio-frequency identification device to determine a unique device signature associated with the predetermined impedance of the at least one radio-frequency identification device, the receiver further being configured to;

mix the RF backscatter with a wireless signal from the transmitter to form an intermediate frequency (IF) signal;

demodulate the IF signal to recover modulation information, the modulation information having a frequency response characteristic of a complex impedance, the at least one radio-frequency identification device predetermined impedance having the complex impedance; and

use the modulation information to determine the unique device signature.

11. The system of claim 10, wherein the wireless signal is a wideband signal.

12. The system of claim 10, further comprising a probing platform which comprises the transmitter and the receiver.

13. The system of claim 10, wherein the predetermined impedance of the at least one radio-frequency identification device defines a unique device signature.

14. The system of claim 10, wherein the system comprises a calibration circuit configured to automatically calibrate the system with regard to round trip delay, the calibration circuit including a splitter, a first mixer configured to mix the RF backscatter with the wireless signal, a second mixer, and a delay line, the splitter configured to split an incoming signal from the transmitter into a first signal that feeds into a local oscillator (LO) port of the first mixer, a second signal that feeds into a delay line that feeds into an RF port of a second mixer, and a third signal that feeds into an LO port of the second mixer.

15. The system of claim 10, wherein the at least one radio-frequency identification device is a passive device.

16. The system of claim 10, wherein a calibration circuit is configured to substantially calibrate for wireless transmission issues associated with a transmission medium, the calibration circuit including a splitter, a first mixer configured to mix the RF backscatter with the wireless signal, a second mixer, and a delay line, the splitter configured to split an incoming signal from the transmitter into a first signal that feeds into a local oscillator (LO) port of the first mixer, a second signal that feeds into a delay line that feeds into an RF port of a second mixer, and a third signal that feeds into an LO Port of the second mixer.

17. The system of claim 10, wherein the receiver is configured to determine at least one of range, azimuth, or elevation from the portion of the wireless signal scattered from the at least one radio-frequency identification device.

18. The system of claim 10, wherein the receiver is configured to discriminate between a plurality of radio-frequency identification devices using a unique device signature associated with each of the radio-frequency identification devices.