Subsoil moisture monitoring system including battery-less wireless chipless sensors

Patent metadata

Field	Value
Publication number	US-2023221274-A1
Application number	US-202318123042-A
Country	US
Kind code	A1
Filing date	Mar 17, 2023
Priority date	Oct 26, 2020
Publication date	Jul 13, 2023
Grant date	—

Abstract

A batteryless, chipless, sensor is disclosed which includes a substrate, at least two conductive strips disposed on the substrate, a passivation layer encasing the substrate and the at least two conductive strips, wherein the conductive strips are adapted to respond to an interrogation signal from a reader having a first polarization, with a response signal at a second polarization different than the first polarization.

First claim

1 . A batteryless, chipless, sensor, comprising:
a substrate; two or more conductive strips coupled to each other and disposed in a meandered profile on the substrate; and a passivation layer encasing the substrate and the two or more conductive strips, wherein the conductive strips are adapted to respond to an interrogation signal from a reader having a first polarization, with a response signal at a second polarization different than the first polarization, wherein resonant frequency of the sensor is inversely related to number of strips of the two or more conductive strips such that when the number of strips increases from 2 to 6, the resonant frequency is reduced from 2.9 GHz to 1.6 GHz.

2 . The sensor of claim 1 , wherein each of the two or more conductive strips are made of metal.

3 . The sensor of claim 2 , wherein the metal is biodegradable including zinc.

4 . The sensor of claim 1 , wherein the substrate is made of acrylic.

5 . The sensor of claim 1 , wherein each of the two or more conductive strips are about 6 cm to about 10 cm.

6 . The sensor of claim 2 , wherein the metal is non-biodegradable including copper.

7 . The sensor of claim 1 , wherein the lumped parameters are defined based on:

L
meander

=

0.2
L
⁢

{

[

1.4813

log
⁡
(

2
⁢
L

a

)

]

1.012

-
0.6188

}

⁢
μH

C
meander

=

C
bend

N

where N is the number of bends in the meandered profile,
L is the total length of the meander profile,
a is the radius of the trace, and
C bend is the capacitance between adjacent bends

8 . The sensor of claim 7 , wherein the resistance of the sensor is determined based on:

R
rad

=

34.15

(

2
⁢
π
⁢

(

L
-

2
⁢
wN

)

λ

)

1.8

where w is the gap between the bends, and
λ is the wavelength.

9 . The sensor of claim 8 , wherein N is between 1 and 10.

10 . The sensor of claim 1 , wherein the passivation layer is a polymer coating.

11 . A system of determining soil conditions, comprising:
one or more ground interrogating devices, each configured to radiate a wireless interrogating signal at a first polarization; a plurality of ground-embedded battery-less and chipless sensors, each comprising:
a substrate,
at least two conductive strips coupled to each other and disposed in a meandered profile on the substrate, and
a passivation layer encasing the substrate and the at least two conductive strips,
wherein the conductive strips are adapted to receive the interrogation signal from the one or more ground interrogating devices, and in response thereto provide a response signal at a second polarization different than the first polarization; wherein the response signal corresponds to a plurality of soil variable associated with soil conditions, and
wherein resonant frequency of the sensor is inversely related to number of strips of the two or more conductive strips such that when the number of strips increases from 2 to 6, the resonant frequency is reduced from 2.9 GHz to 1.6 GHz;
a server configured to receive signals from the one or more ground interrogating devices; and
at least one input/output device in communication with the server and configured to provide control signals to the one or more ground interrogating devices and to receive data associated with the soil variable associated with soil conditions.

12 . The system of claim 11 , wherein the conductive strips are made of metal.

13 . The system of claim 12 , wherein the metal is biodegradable including zinc.

14 . The system of claim 11 , wherein the substrate is made of acrylic.

15 . The system of claim 11 , wherein the at least two conductive strips are about 6 cm to about 10 cm.

16 . The system of claim 12 , wherein the metal is non-biodegradable including copper.

17 . The system of claim 11 , wherein the lumped parameters are defined based on:

L
meander

=

0.2
L
⁢

{

[

1.4813

log
⁡
(

2
⁢
L

a

)

]

1.012

-
0.6188

}

⁢
μH

C
meander

=

Assignees

• Purdue Research Foundation

Inventors

• Gopalakrishnan Sarath
• Waimin Jose
• Rahimi Rahim
• Raghunathan Nithin

Classifications

• G01N33/246 Primary

  for water content · CPC title

• G01N27/223 Primary

  for determining moisture content, e.g. humidity (rain detectors on vehicle windows B60S1/0825) · CPC title

• G01N2033/245

  Physics · mapped topic

• G01N33/245

  for agricultural purposes · CPC title