# US 12,181,572 B1 · Scattering aperture imaging method and device, system, and storage medium

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- Number: US 12,181,572 B1
- Document ID: US12181572B1
- Status: Granted
- Kind: B1
- Application number: 18/652,208
- Filed: 2024-05-01
- Granted: 2024-12-31
- Earliest claimed: 2024-01-26
- Assignees: University of Electronic Science and Technology of China
- Applicants: University of Electronic Science and Technology of China
- Inventors: Jiang Qian; Jiayang Wu; Haitao Lyu; Guangcai Sun
- Web page: https://patentgrep.com/patent/US12181572B1

## CPC

- G01S 13/9011: {with frequency domain processing of the SAR signals in azimuth (G01S13/9005 takes precedence)}
- G01S 7/2955: {Means for determining the position of the radar coordinate system for evaluating the position data of the target in another coordinate system (G01S7/24 takes precedence; sighting devices adapted for indirect laying of fire F41G3/16; inertial navigation G01C21/16)}
- G01S 13/46: Indirect determination of position data
- G01S 13/90: using synthetic aperture techniques {, e.g. synthetic aperture radar [SAR] techniques}
- G01S 13/343: {using sawtooth modulation}
- G01S 2013/0245: {Radar with phased array antenna}
- G01S 2013/464: {using only the non-line-of-sight signal(s), e.g. to enable survey of scene 'behind' the target only the indirect signal is evaluated}
- G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES

## Abstract

Provided are a scattering aperture imaging method and a device, a system and a storage medium. The method mainly includes four steps of scattering point position estimation, azimuth resampling, range compensation and synthetic aperture radar imaging. A phased array radar with a fixed position is used for NLOS imaging, and the radar can control a beam to scan in space, which is equivalent to a scattering aperture moving along a relay surface. Therefore, the method can realize converting NLOS imaging into LOS synthetic aperture radar imaging, which can be suitable for the situation that a relay surface is rough and the relay surface with more complicated surface condition, thus widening the application range of radar NLOS imaging.

## Claims

### Claim 1

A scattering aperture imaging method, wherein in a situation that a phased array radar faces towards a rough relay surface, a projection of a beam main lobe of the phased array radar on the rough relay surface is regarded as a virtual aperture, and scattering of a radar signal on the virtual aperture is equivalent to scattering of the radar signal occurring at a scattering point in the virtual aperture, the virtual aperture being a scattering aperture and the scattering point being a main scatterer, and the scattering aperture imaging method comprises:
estimating a position of the main scatterer;
performing, based on the position of the main scatterer, azimuth resampling through interpolation, to obtain sampling points showing a uniform linear array in an azimuth direction;
performing range compensation on the radar signal, to measure a signal propagation path of the radar signal from the main scatterer to an object to the main scatterer; and
performing synthetic aperture radar imaging.

### Claim 2 (depends on 1)

The scattering aperture imaging method according to claim 1, wherein the estimating the position of the main scatterer comprises:
estimating, based on each pulse of echoes of the rough relay surface, an azimuth angle of the main scatterer relative to a radar and a range of the main scatterer relative to the radar, to thereby obtain a position estimation value of the main scatterer.

### Claim 3 (depends on 2)

The scattering aperture imaging method according to claim 2, wherein the estimating, based on each pulse of echoes of the rough relay surface, an azimuth angle of the main scatterer relative to a radar and a range of the main scatterer relative to the radar, to thereby obtain a position estimation value of the main scatterer, comprises:
estimating, based on each pulse of the echoes of the rough relay surface, the azimuth angle of the main scatterer relative to the radar and the range of the main scatterer relative to the radar by using a sum-difference beam method and a multiple signal classification (MUSIC) algorithm, to thereby obtain the position estimation value of the main scatterer.

### Claim 4 (depends on 1)

The scattering aperture imaging method according to claim 1, wherein the performing, based on the position of the main scatterer, azimuth resampling through interpolation, to obtain sampling points showing a uniform linear array in an azimuth direction, comprises:
performing the azimuth resampling with a sampling interval satisfying a formula 1:
Δ
⁢
x
<
λ
2
,
(
1
)
where Δx represents the sampling interval, and λ represents a wavelength of the radar signal.

### Claim 5 (depends on 1)

The scattering aperture imaging method according to claim 1, wherein the performing range compensation on the radar signal, to measure the signal propagation path of the radar signal from the main scatterer to the object to the main scatterer comprises:
dividing the signal propagation path of the radar signal into two segments comprising: a first segment from the radar to the main scatterer to the radar, and a second segment from the main scatterer to the object to the main scatterer; where a range between the radar and the main scatterer is denoted as x1, a range between the main scatterer and the object is denoted as x2, and a range from the radar to the main scatterer and then to the object is denoted as x, which is expressed in a formula 2:
x=x1+x2 (2),
where an echo s(t) of a de-frequency modulation linear frequency modulation (LFM) signal after three reflections is expressed as a formula 3:
s(t)=exp(2jπfc(t1+t2)−jπKrt12−jπKrt22+2jπKrtt1+2jπKrtt2−2jπKrt1t2) (3),
where fc represents a radar carrier frequency, Kr represents a modulation frequency of an LFM signal, t represents a time, t1 represents a propagation time of the radar signal between the radar and the main scatterer, and t2 represents a propagation time of the radar signal between the main scatterer and the object;
where t1 and x1 satisfies a relationship expressed in a formula 4, and t2 and x2 satisfies a relationship expressed in a formula 5:
t
1
=
2
⁢
x
1
c
;
(
4
)
t
2
=
2
⁢
x
2
c
,
(
5
)
where c represents a speed of light;
constructing a range compensation term x(t) of the echo s(t), which is expressed in a formula 6:
x(t)=exp(−2jπfct1+jπKrt12−2jπKrtt1) (6),
multiplying the range compensation term with the echo in a time domain to obtain the echo after range compensation s′(t) expressed in a formula 7:
s′(t)=s(t)x(t)=exp(2jπfct2−jπKrt22+2jπKrtt2−2jπKrt1t2) (7),
where the formula 7 has no related term of t1 excepting a complex constant term exp(−2jπKrt1t2), and s′(t) is consistent with the de-frequency modulation LFM signal with a time delay of t2 in the form;
constructing a compensation term hn expressed in a formula 8 for an echo with an azimuth index n after range compensation:
h
n
=
exp
⁡
(
4
⁢
j
⁢
π
⁢
x
n
-
x
¯
λ
)
,
(
8
)
where λ represents a wavelength of the radar signal, xn represents a position of the main scatterer in a range direction corresponding to the echo with the azimuth index n, and x represents an average position of the main scatterer in the range direction;
multiplying the echo after range compensation s′(t) by the corresponding compensation term hn, to thereby compensate the main scatterer to a plane x=x.

### Claim 6 (depends on 5)

The scattering aperture imaging method according to claim 5, wherein after the performing range compensation, a non-line-of-sight (NLOS) imaging problem of the phased array radar is transformed into a line-of-sight imaging problem of a synthetic aperture radar, and
wherein the performing synthetic aperture radar imaging comprises: performing the synthetic aperture radar imaging by using a synthetic aperture radar imaging algorithm.

### Claim 7 (depends on 1)

A multi-user modulation classification system, comprising:
a memory with a computer program stored therein; and
a processor, configured to execute the computer program to implement the scattering aperture imaging method according to claim 1.

### Claim 8 (depends on 1)

A non-transitory readable storage medium with one or more programs stored therein, wherein the one or more programs, when executed by one or more processors, is configured to implement the scattering aperture imaging method according to claim 1.

### Claim 9

A scattering aperture imaging method device, comprising:
a position estimation module, configure to estimate a position of a main scatterer;
a resampling module, configured to perform, based on the position of the main scatterer, azimuth resampling through interpolation, to obtain sampling points showing a uniform linear array in an azimuth direction;
a compensation module, configured to perform range compensation on a radar signal, to measure a signal propagation path of the radar signal from the main scatterer to an object to the main scatterer; and
an imaging module, configured to perform synthetic aperture radar imaging.

### Claim 10 (depends on 9)

The scattering aperture imaging device according to claim 9, wherein the compensation module is further configured to:
divide the signal propagation path of the radar signal into two segments comprising: a first segment from the radar to the main scatterer to the radar; and a second segment from the main scatterer to the object to the main scatterer; where a range between the radar and the main scatterer is denoted as x1, a range between the main scatterer and the object is denoted as x2, and a range from the radar to the main scatterer and then to the object is denoted as x, which is expressed in a formula 2:
x=x1+x2 (2),
where an echo s(t) of a de-frequency modulation linear frequency modulation (LFM) signal after three reflections is expressed as a formula 3:
s(t)=exp(2jπfc(t1+t2)−jπKrt12−jπKrt22+2jπKrtt1+2jπKrtt2−2jπKrt1t2) (3),
where fc represents a radar carrier frequency, Kr represents a modulation frequency of an LFM signal, t represents a time, t1 represents a propagation time of the radar signal between the radar and the main scatterer, and t2 represents a propagation time of the radar signal between the main scatterer and the object;
where t1 and x1 satisfies a relationship expressed in a formula 4, and t2 and x2 satisfies a relationship expressed in a formula 5:
t
1
=
2
⁢
x
1
c
;
(
4
)
t
2
=
2
⁢
x
2
c
,
(
5
)
where c represents a speed of light;
construct a range compensation term x(t) of the echo s(t), which is expressed in a formula 6:
x(t)=exp(−2jπfct1+jπKrt12−2jπKrtt1) (6),
multiply the range compensation term with the echo in a time domain to obtain the echo after range compensation s′(t) expressed in a formula 7:
s′(t)=s(t)x(t)=exp(2jπfct2−jπKrt22+2jπKrtt2−2jπKrt1t2) (7),
where the formula 7 has no related term of t1 excepting a complex constant term exp(−2jπKrt1t2), and s′(t) is consistent with the de-frequency modulation LFM signal with a time delay of t2 in the form;
construct a compensation term hn expressed in a formula 8 for an echo with an azimuth index n after range compensation:
h
n
=
exp
⁡
(
4
⁢
j
⁢
π
⁢
x
n
-
x
¯
λ
)
,
(
8
)
where λ represents a wavelength of the radar signal, xn represents a position of the main scatterer in a range direction corresponding to the echo with the azimuth index n, and x represents an average position of the main scatterer in the range direction;
multiply the echo after range compensation s′(t) by the corresponding compensation term hn, to thereby compensate the main scatterer to a plane x=x.