# US 2025/0146845 A1 · Method and device of amplitude-phase inconsistency in-situ correction for the multi-channel capacitive sensor

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- Number: US 2025/0146845 A1
- Document ID: US20250146845A1
- Status: Published application
- Kind: A1
- Application number: 18/581,352
- Filed: 2024-02-19
- Published: 2025-05-08
- Earliest claimed: 2023-11-08
- Assignees: Huazhong University of Science and Technology
- Applicants: Huazhong University of Science and Technology
- Inventors: Hong Ma; Yuerong Zhang; Hua Zhang
- Web page: https://patentgrep.com/patent/US20250146845A1

## CPC

- G01D 18/00: Testing or calibrating apparatus or arrangements provided for in groups G01D1/00 - G01D15/00
- G01D 5/24: by varying capacitance
- G01D: MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR

## Abstract

The disclosure provides a method and device for correction of the multi-channel capacitive sensor. The method includes: under calibrating mode, inputting the calibration signal from the calibration capacitance network module to the multi-channel capacitive sensor, and measuring the output complex voltage at each calibration frequency point; selecting any channel as a reference channel, combining each-channel three-admittance parameters with the output complex voltages at each calibration frequency point, calculating each-channel amplitude-phase correction coefficient relative to the reference channel; under operating mode, inputting a carrier signal to the multi-channel capacitive sensor through the multiple DoF sensitive probe, and measuring the output complex voltages under actual operation; and multiplying the output complex voltages by the correction coefficients, thereby obtaining the multiple sensing channel output signals.

## Claims

### Claim 1

A method of amplitude-phase inconsistency in-situ correction for a multi-channel capacitive sensor, comprising:
S1: under a calibrating mode, inputting a calibration signal from a calibration capacitance network module to the multi-channel capacitive sensor, and measuring output complex voltages of the multi-channel capacitive sensor at each calibration frequency point;
S2: equating the calibration capacitance network module to multi-channel three-admittance networks, measuring port scattering parameters of each equivalent three-admittance network, and extracting three-admittance parameters of each-channel at each calibration frequency point;
S3: selecting any channel of the multi-channel capacitive sensor as a reference channel; calculating an amplitude-phase correction coefficient of each-channel relative to the reference channel through combining the three-admittance parameters of each-channel at each calibration frequency point and the output complex voltages of the multi-channel capacitive sensor at each calibration frequency point;
S4: under an operating mode, inputting a carrier signal to the multi-channel capacitive sensor through a multiple degree of freedom (DoF) sensitive probe, and measuring the output complex voltages of the multi-channel capacitive sensor under actual operation;
S5: multiplying the output complex voltages of the multi-channel capacitive sensor under actual operation by the amplitude-phase correction coefficients, thereby obtaining multiple sensing channel output signals after eliminating inter-channel amplitude-phase inconsistency,
wherein the calibration capacitance network module comprises a one-to-multiple equal-amplitude in-phase power splitter and a multi-channel calibration capacitance network, and each channel of which comprises three capacitors with the same nominal value and connected in a Y-shaped manner, and two single-pole double-throw switches connected to the capacitors.

### Claim 2 (depends on 1)

The method of the amplitude-phase inconsistency in-situ correction for the multi-channel capacitive sensor according to claim 1, wherein the method of extracting the three-admittance parameters of each channel at each calibration frequency point comprises:
equating the calibration capacitance network module to the three-admittance networks, measuring a scattering parameter matrix of an ith-channel three-admittance network at each frequency point, thereby calculating the amplitudes and phases of the scattering parameters at each frequency point;
smoothing curves of amplitude and phase to frequency of the scattering parameters at each frequency point, thus obtaining a smoothed scattering parameter matrix of the ith-channel three-admittance network;
calculating the admittance matrix at each frequency point of the ith-channel three-admittance network according to its smoothed scattering parameter matrix and its termination impedances;
establishing variable optimization equations in the ith-channel three-admittance network based on its admittance matrix and solving its three-admittance parameters at each calibration frequency point.

### Claim 3 (depends on 1)

The method of amplitude-phase inconsistency in-situ correction for the multi-channel capacitive sensor according to claim 1, wherein a first channel of the multi-channel capacitive sensor is selected as the reference channel, and the amplitude-phase inconsistency correction coefficient of an ith sensing channel at each calibration frequency point relative to the reference channel is:
β
.
1
⁢
i
(
f
)
=
V
.
O
⁢
1
(
f
)
V
.
Oi
(
f
)
·
h
.
i
(
Y
i
⁢
1
(
f
)
,
Y
i
⁢
2
(
f
)
,
Y
i
⁢
3
(
f
)
)
h
.
i
(
Y
1
⁢
1
(
f
)
,
Y
12
(
f
)
,
Y
13
(
f
)
)
,
wherein {dot over (β)}1i(f) is the amplitude-phase inconsistency correction coefficient of the ith sensing channel relative to the reference channel, {dot over (V)}O1(f) is the output complex voltage of the reference channel in the multi-channel capacitive sensor, {dot over (V)}Oi(f) is the output complex voltage of the multi-channel capacitive sensor, {dot over (h)}i(Yi1(f), Yi2(f), Yi3(f)) is a complex transfer function of an ith-channel equivalent calibration admittance network, {dot over (h)}1(Y11(f), Y12(f), Y13(f)) is a complex transfer function of the reference channel in the equivalent calibration admittance network, and Yi1(f), Yi2(f), Yi3(f) are the three-admittance parameters of the ith-channel equivalent calibration admittance network at each calibration frequency point.

### Claim 4 (depends on 2)

The method of amplitude-phase inconsistency in-situ correction for the multi-channel capacitive sensor according to claim 2, wherein a first channel of the multi-channel capacitive sensor is selected as the reference channel, and the amplitude-phase inconsistency correction coefficient of an ith sensing channel at each calibration frequency point relative to the reference channel is:
β
.
1
⁢
i
(
f
)
=
V
.
O
⁢
1
(
f
)
V
.
Oi
(
f
)
·
h
.
i
(
Y
i
⁢
1
(
f
)
,
Y
i
⁢
2
(
f
)
,
Y
i
⁢
3
(
f
)
)
h
.
i
(
Y
1
⁢
1
(
f
)
,
Y
12
(
f
)
,
Y
13
(
f
)
)
,
wherein {dot over (β)}1i(f) is the amplitude-phase inconsistency correction coefficient of the ith sensing channel relative to the reference channel, {dot over (V)}O1(f) is the output complex voltage of the reference channel in the multi-channel capacitive sensor, {dot over (V)}Oi(f) is the output complex voltage of the multi-channel capacitive sensor, {dot over (h)}i(Yi1(f), Yi2(f), Yi3(f)) is a complex transfer function of an ith-channel equivalent calibration admittance network, {dot over (h)}1(Y11(f), Y12(f), Y13(f)) is a complex transfer function of the reference channel in the equivalent calibration admittance network, and Yi1(f), Yi2(f), Yi3(f) are the three-admittance parameters of the ith-channel equivalent calibration admittance network at each calibration frequency point.

### Claim 5 (depends on 1)

The method of amplitude-phase inconsistency in-situ correction for the multi-channel capacitive sensor according to claim 1, wherein the output complex voltage of the multi-channel capacitive sensor at each calibration frequency point is: {dot over (V)}Oi(f)=Ii(f) j·Qi(f),
{
I
i
(
f
)
=
2
N
·
∑
n
=
1
N
⁢
{
i
i
(
n
)
⁢
cos
⁢
(
2
⁢
π
·
Δ
⁢
f
·
n
f
D
⁢
D
⁢
C
)
}
Q
i
(
f
)
=
-
2
N
·
∑
n
=
1
N
⁢
{
i
i
(
n
)
⁢
sin
⁢
(
2
⁢
π
·
Δ
⁢
f
·
n
f
D
⁢
D
⁢
C
)
}
,
wherein ii(n) is an output in-phase data sequence after performing a digital orthogonal down-conversion which is sampled by N points with a sampling rate of fDDC, n=1, 2, . . . , N, and Δf is a frequency difference between a local oscillator frequency fLO of the digital orthogonal down-conversion and a calibration input signal frequency f.

### Claim 6

A device of amplitude-phase inconsistency in-situ correction for a multi-channel capacitive sensor, comprising:
a calibration capacitance network module comprising a one-to-multiple equal-amplitude in-phase power splitter and a multi-channel calibration capacitance network, wherein each channel comprises three capacitors with the same nominal value and connected in a Y-shaped manner, and two single-pole double-throw switches connected to the capacitors, and under a calibrating mode, an output terminal of the calibration capacitance network is connected to the multi-channel capacitive sensor and configured to receive the calibration input signal;
a multiple degree of freedom (DoF) sensitive probe, wherein each pair of its sensing electrodes is connected to a capacitive sensing channel through two single-pole double-throw switches at a Y-shaped branch position in the one channel calibration capacitance network for receiving capacitive displacement signals under operating mode;
an output signal measuring module configured to measure output complex voltages of the multi-channel capacitive sensor under a calibrating and operating mode;
a vector network analyzer configured to measure port scattering parameters of multiple equivalent three-admittance networks in the calibration capacitance network module;
an amplitude-phase correction parameter calculating module configured to extract three-admittance parameters of each channel at each frequency calibration point based on the port scattering parameters of the equivalent three-admittance network, any channel of the capacitive sensor being selected as a reference channel, and an amplitude-phase correction coefficient of each channel relative to the reference channel being calculated through combining the three-admittance parameters of each-channel at each calibration frequency point and the output complex voltages of the multi-channel capacitive sensor at each calibration frequency point;
a multiple sensing channel output signal acquisition module configured to multiply the output complex voltages of the multi-channel capacitive sensor during actual operation by the amplitude-phase correction coefficients, thereby obtaining multiple sensing channel output signals after eliminating inter-channel amplitude-phase inconsistency.

### Claim 7 (depends on 6)

The device of amplitude-phase inconsistency in-situ correction for the multi-channel capacitive sensor according to claim 6, wherein the amplitude-phase correction parameters calculating module comprises:
a scattering parameter matrix acquisition unit configured to smooth curves of amplitude and phase to frequency of the scattering parameters at each frequency point and obtain a smoothed scattering parameter matrix of an ith-channel three-admittance network;
an admittance matrix calculating unit configured to calculate an admittance matrix at each frequency point of the ith-channel three-admittance network according to its smoothed scattering parameter matrix and its termination impedances;
a three-admittance parameter calculating unit configured to the variable optimization equations in the ith-channel three-admittance network based on its admittance matrix and solve its three-admittance parameters at each calibration frequency point;
a correction coefficient calculating unit configured to select any channel in the capacitive sensor as the reference channel, and the amplitude-phase correction coefficient of each channel relative to the reference channel being calculated through combining the three-admittance parameters of each channel at each calibration frequency point and the output complex voltages of the multi-channel capacitive sensor at each calibration frequency point.

### Claim 8 (depends on 6)

The device of amplitude-phase inconsistency in-situ correction for the multi-channel capacitive sensor according to claim 6, wherein a first channel of the capacitive sensor is selected as the reference channel, and an amplitude-phase inconsistency correction coefficient of an ith sensing channel at each calibration frequency point relative to the reference channel is:
β
.
1
⁢
i
(
f
)
=
V
.
O
⁢
1
(
f
)
V
.
Oi
(
f
)
·
h
.
i
(
Y
i
⁢
1
(
f
)
,
Y
i
⁢
2
(
f
)
,
Y
i
⁢
3
(
f
)
)
h
.
i
(
Y
1
⁢
1
(
f
)
,
Y
12
(
f
)
,
Y
13
(
f
)
)
,
wherein β1i(f) is the amplitude-phase inconsistency correction coefficient of the ith sensing channel relative to the reference channel, {dot over (V)}O1(f) is the output complex voltage of the reference channel in the capacitive sensor, {dot over (V)}Oi(f) is the output complex voltage of the multi-channel capacitive sensor, {dot over (h)}i(Yi1(f), Yi2(f), Yi3(f)) is a complex transfer function of an ith-channel equivalent calibration admittance network, {dot over (h)}1(Y11(f), Y12(f), Y13(f)) is a complex transfer function of a reference channel equivalent calibration admittance network, and Y11(f), Y12(f), Y13(f) is the three-admittance parameters of the ith-channel equivalent calibration admittance network at each calibration frequency point.

### Claim 9 (depends on 7)

The device of amplitude-phase inconsistency in-situ correction for the multi-channel capacitive sensor according to claim 7, wherein a first channel of the multi-channel capacitive sensor is selected as the reference channel, and an amplitude-phase inconsistency correction coefficient of an ith sensing channel at each calibration frequency point relative to the reference channel is:
β
.
1
⁢
i
(
f
)
=
V
.
O
⁢
1
(
f
)
V
.
Oi
(
f
)
·
h
.
i
(
Y
i
⁢
1
(
f
)
,
Y
i
⁢
2
(
f
)
,
Y
i
⁢
3
(
f
)
)
h
.
i
(
Y
1
⁢
1
(
f
)
,
Y
12
(
f
)
,
Y
13
(
f
)
)
,
wherein {dot over (β)}1i(f) is the amplitude-phase inconsistency correction coefficient of the ith sensing channel relative to the reference channel, {dot over (V)}O1(f) is the output complex voltage of the reference channel in the capacitive sensor, {dot over (V)}Oi(f) is the output complex voltage of the multi-channel capacitive sensor, {dot over (h)}i(Yi1(f), Yi2(f), Yi3(f)) is a complex transfer function of an ith channel equivalent calibration admittance network, {dot over (h)}1(Y11(f), Y12(f), Y13(f)) is a complex transfer function of a reference channel equivalent calibration admittance network, and Y11(f), Y12(f), Y13(f) is the three-admittance parameters of the ith-channel equivalent calibration admittance network at each calibration frequency point.

### Claim 10 (depends on 6)

The device of amplitude and phase inconsistency in-situ correction for the multi-channel capacitive sensor according to claim 6, wherein the output complex voltage of the multi-channel capacitive sensor at each calibration frequency point is: {dot over (V)}Oi(f)=Ii(f)+j·Qi(f),
{
I
i
(
f
)
=
2
N
·
∑
n
=
1
N
⁢
{
i
i
(
n
)
⁢
cos
⁢
(
2
⁢
π
·
Δ
⁢
f
·
n
f
D
⁢
D
⁢
C
)
}
Q
i
(
f
)
=
-
2
N
·
∑
n
=
1
N
⁢
{
i
i
(
n
)
⁢
sin
⁢
(
2
⁢
π
·
Δ
⁢
f
·
n
f
D
⁢
D
⁢
C
)
}
,
wherein ii(n) is an output in-phase data sequence after digital orthogonal down-conversion which is sampled by N points with sampling rate of fDDC, n=1, 2, . . . , N, and Δf is a frequency difference between a local oscillator frequency fLO of the digital orthogonal down-conversion and a calibration input signal frequency f.