Transmission delay based RFID tag

• US 8,736,452 B1
• Filed: 03/13/2008
• Issued: 05/27/2014
• Est. Priority Date: 09/28/2006
• Status: Expired due to Fees

• Current Assignee: Louisiana Tech Research Corporation
• Original Assignee: Louisiana Tech University
• Inventors: Varahramyan, Khodadad, Agarwal, Mangilal, Shrestha, Sudhir, Vemagiri, Jeevan Kumar, Chamarti, Aravind, Ramisetti, Sireesha, Balachandran, Mercyma Dee
• Primary Examiner(s): Zimmerman, Brian
• Assistant Examiner(s): Nguyen, An T
• Application Number:
  US12/048,019
• Time in Patent Office: 2,266 Days
• Field of Search: 343/745, 343/905, 343/906, 340/540, 340/568.1, 340/572.1, 340/572.5, 340/572.7, 340/500, 340/531, 340/539.1, 340/539.26, 340/539.27, 340/10.1
• US Class Current: 340/572.7
• CPC Class Codes: G01N 27/227 Sensors changing capacitance upon adsorption or absorption of fluid components, e.g. electrolyte-insulator-semiconductor sensors, MOS capacitors G01N27/225 takes precedence
• CPC Class Codes: G01N 33/0047 Organic compounds
• CPC Class Codes: G06K 19/0672 with resonating marks
• CPC Class Codes: H04Q 2209/47 using RFID associated with sensors
• CPC Class Codes: H04Q 2213/13095 PIN / Access code, authentication
• CPC Class Codes: H04Q 9/00 Arrangements in telecontrol or telemetry systems for selectively calling a substation from a main station, in which substation desired apparatus is selected for applying a control signal thereto or for obtaining measured values therefrom

Abstract

A chipless RFID tag system having a transmitter sending an input signal and a tag substrate. An ID generation circuit on the tag relies on microstrip transmission line patterns which are pre-designed to generate a unique code. The ID generating circuit may be designed based upon the transmission line properties, including signal delay, and/or reflection, and/or phase change. The tag may be formed on a flexible substrate having at least one microstrip and the microstrip having a first portion with a first impedance and a second portion with a second impedance different from the first impedance. The tag may further include a microstrip antenna for communication with the transmitter and a receiver system. The tag may also include sensors for detection of desired substances of interest. The system may further include a receiver detecting at least two reflections from an interface of first and second impedances and identifying relative time domain positions of the reflections to one another.

Claims

1. A passive wireless sensor strip comprising:

a substrate;

a strip antenna positioned on the substrate, and the strip antenna having an alterable reflection characteristic; and

a passive sensor device positioned on the substrate and connected to the strip antenna, and the passive sensor device altering the reflection characteristics of the strip antenna when exposed to ethylene gas;

wherein the sensor device comprises a layer of semi-conductor material positioned between two conducting layers; and

wherein at least one of the conducting layers comprises an antenna lead connecting the strip antenna to the passive sensor device.

3. The passive wireless sensor strip of claim 1, wherein the layer of semi conductor material comprises tin dioxide.

4. The passive wireless sensor strip of claim 1, wherein the target condition is ethylene gas.

5. The passive wireless sensor strip of claim 1, wherein the substrate is flexible.

8. The passive wireless sensor strip of claim 3, wherein the tin dioxide is doped.

9. The passive wireless sensor strip of claim 1, wherein the sensor device changes capacitance upon exposure to a target gas, the target condition being whether the strip antenna is exposed to the target gas.

10. The passive wireless sensor strip of claim 1, wherein the sensor device changes capacitance upon exposure to the ethylene gas.

2. A passive wireless sensor strip comprising:

a substrate;

a strip antenna positioned on the substrate, and the strip antenna having an alterable reflection characteristic; and

a passive sensor device positioned on the substrate and connected to the strip antenna, and the passive sensor device altering the reflection characteristics of the strip antenna when exposed to a target condition;

wherein the sensor device changes capacitance upon exposure to ethylene gas, the target condition being whether the strip antenna is exposed to the ethylene gas.

6. The passive wireless sensor strip of claim 2, wherein the sensor device comprises a layer of semi conductor material positioned between two conducting layers.

7. The passive wireless sensor strip of claim 2, further comprising an antenna lead connecting the strip antenna to the passive sensor device, and one of the conducting layers comprises the antenna lead.