Transmission delay based RFID tag

• US 8,179,231 B1
• Filed: 09/28/2007
• Issued: 05/15/2012
• Est. Priority Date: 09/28/2006
• Status: Active Grant

• Current Assignee: Louisiana Tech Research Corporation
• Original Assignee: Louisiana Tech Research Foundation; A Division Of Louisiana Tech University Foundation, Inc.
• Inventors: Agarwal, Mangilal, Chamarti, Aravind, Ramisetti, Sireesha, Varahramyan, Khodadad, Shrestha, Sudhir, Vemagiri, Jeevan Kumar
• Primary Examiner(s): Wu, Daniel
• Assistant Examiner(s): MA, KAM WAN
• Application Number:
  US11/864,159
• Time in Patent Office: 1,691 Days
• Field of Search: 340/10.1, 340/572.1, 340/572.5, 340/572.9, 298/46, 235/492
• US Class Current: 340/10.1
• CPC Class Codes: G06K 19/0672 with resonating marks
• CPC Class Codes: Y10T 29/49155 Manufacturing circuit on or in base

Abstract

A chipless RFID tag system having a transmitter sending an input signal and a tag substrate. The tag substrate has at least one microstrip and the microstrip has a first portion with a first impedance and a second portion with a second impedance different from the first impedance. The system further includes a receiver detecting at least two reflections from an interface of the first and second impedances and identifying relative time domain positions of the reflections to one another.

Claims

1. A chipless RFID tag system comprising:

a transmitter sending an input signal;

a chipless RFID tag comprising a tag substrate having a first microstrip and a second microstrip, wherein the second microstrip is at least twice as long as the first microstrip and the first and second microstrips have substantially uniform impedance along its length;

wherein said chipless RFID tag further comprises at least one tap positioned between the first and second microstrips allowing one-way transmission of the input signal from the second to the first microstrip;

wherein the first and second microstrips have a common input port to receive said input signal;

wherein the first microstrip outputs a tag response signal determined by said at least one tap.

2. The chipless RFID tag system according to claim 1, wherein the tap is positioned such that a transmission delay in the second microstrip is greater than a duration of the input signal.

3. The chipless RFID tag system according to claim 2, wherein the tap is positioned such that the transmission delay is a multiple of the duration of the input signal.

4. The chipless RFID tag system according to claim 1, wherein the second microstrip is terminated with a load which is approximately equal to a characteristic impedance of the second microstrip.

5. The chipless RFID tag system according to claim 1, wherein multiple taps are positioned between said first and second microstrips.

6. The chipless RFID tag system according to claim 1, wherein the second microstrip runs along a meandering path.