SYSTEM AND METHOD FOR ESTIMATING RANGE TO AN RFID TAG

• US 20160187478A1
• Filed: 03/07/2016
• Published: 06/30/2016
• Est. Priority Date: 02/03/2012
• Status: Active Grant

• Current Assignee: Amtech Systems LLC (Roper Technologies, Inc.)
• Original Assignee: Amtech Systems LLC (Roper Technologies, Inc.)
• Inventors: Melville, Michael George, Elson, John Todd
• Granted Patent: US 9,841,500 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01S 13/08 Systems for measuring distance only indirect measurement G01S13/46
• CPC Class Codes: G01S 13/325 using transmission of coded signals, e.g. P.S.K. signals
• CPC Class Codes: G01S 13/36 with phase comparison between the received signal and the contemporaneously transmitted signal
• CPC Class Codes: G01S 13/584 adapted for simultaneous range and velocity measurements
• CPC Class Codes: G01S 13/75 using transponders powered from received waves, e.g. using passive transponders , or using passive reflectors
• CPC Class Codes: G01S 13/84 for distance determination by phase measurement
• CPC Class Codes: G01S 13/878 Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector G01S13/874 takes precedence
• CPC Class Codes: G01S 13/91 for traffic control G01S13/93 takes precedence
• CPC Class Codes: G06K 7/10366 the interrogation device being adapted for miscellaneous applications
• CPC Class Codes: G06K 7/10425 the interrogation device being arranged for interrogation of record carriers passing by the interrogation device

Abstract

The a system for measuring distance between an RFID reader and tag, including an adaptive linear combiner, which is a tapped delay line with controllable weights on each tap, and outputs that are summed and subtracted from a reference to produce an error signal. After a sufficient number of cycles, the weight distribution indicates the delay of the received signal with respect to the reference, and by extension determines the distance between the tag and receiver.

Claims

1. A system for determining horizontal distance from a plurality of antennas to a backscatter RFID tag comprising:

a transmitter for transmitting a transmitted modulated signal to the tag via first and second antennas,

a first receiver for receiving a first delayed modulated backscattered signal from the tag via said first antenna;

a second receiver for receiving a second delayed modulated backscattered signal from the tag via said second antenna; and

a first linear adaptive combiner which is a tapped delay line with controllable weights on each tap, and outputs that are summed and subtracted from a reference to produce a first error signal;

a second linear adaptive combiner which is a tapped delay line with controllable weights on each tap, and outputs that are summed and subtracted from said reference to produce a second error signal;

wherein modulation in the backscattered signal received by said first antenna is input to said first adaptive linear combiner, and said transmitted modulated signal is said reference to said first combiner;

wherein modulation in the backscattered signal received by said second antenna is input to said second adaptive linear combiner, and said transmitted modulated signal is said reference to said second combiner;

and wherein weights for said taps of said first and second linear adaptive combiners are approximately zero for all of said taps except for respective first and second combiner taps corresponding to the first and second delays of the backscattered signal and wherein the horizontal distance from the RFID tag to each of said antennas is determined from said delays and said height.