Subsoil moisture monitoring system including battery-less wireless chipless sensors

Patent metadata

Field	Value
Publication number	US-11635402-B2
Application number	US-202117510999-A
Country	US
Kind code	B2
Filing date	Oct 26, 2021
Priority date	Oct 26, 2020
Publication date	Apr 25, 2023
Grant date	Apr 25, 2023

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

The invention claimed is:

1. A batteryless, chipless, sensor, 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 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 the lumped parameters are defined based on:

L
meander

=

0
.
2

⁢
L
⁢

{

[

1
.
4

⁢
813
⁢

log
⁡
(

2
⁢
L

a

)

]

1
.
0

⁢
1
⁢
2

-

0
.
6

⁢
1
⁢
88

}

⁢
µH

C

m
⁢
e
⁢
a
⁢
nder

=

C

b
⁢
e
⁢
n
⁢
d

N

where N is the number of bends in the meandered profile,
L is the total length of the meander profile,
α is the radius of the trace, and

C bend is the capacitance between adjacent bends.

2. The sensor of claim 1 , wherein the conductive strips are made of metal.

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

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

5. The sensor of claim 1 , wherein the at least two conductive strips are about 6 cm to about 10 cm.

6. The sensor of claim 1 , wherein the substrate is made of polylactic acid (PLA).

7. The sensor of claim 6 , wherein the conductive strips are made of zinc.

8. The sensor of claim 1 , wherein the resistance of the sensor is determined based on:

R
rad

=

3
⁢

4
.
1

⁢
5
⁢

(

2
⁢
π
⁢

(

L
-

2
⁢
w
⁢
N

)

λ

)

1
.
8

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

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

10. 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;
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,

wherein the lumped parameters are defined based on:

L
meander

=

Assignees

• Purdue Research Foundation

Inventors

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

Classifications

• G01N27/223 Primary

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

• G01N33/246 Primary

  for water content · CPC title

• G01N2033/245

  Physics · mapped topic

• G01N33/245

  for agricultural purposes · CPC title