# US 11,994,603 B1 · Method of sparse array oriented approach for DOA estimation of grating lobe target filtering

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- Number: US 11,994,603 B1
- Document ID: US11994603B1
- Status: Granted
- Kind: B1
- Application number: 18/381,453
- Filed: 2023-10-18
- Granted: 2024-05-28
- Earliest claimed: 2023-02-20
- Assignees: Shanghai Geometrical Perception and Learning Co., Ltd.
- Applicants: Shanghai Geometrical Perception and Learning Co., Ltd.
- Inventors: Yue Zhao; Mingyu Zhou; Songhua Shi; Dan Xue
- Web page: https://patentgrep.com/patent/US11994603B1

## CPC

- G01S 3/143: {by vectorial combination of signals derived from differently oriented antennae}
- G01S 3/74: Multi-channel systems specially adapted for direction-finding, i.e. having a single antenna system capable of giving simultaneous indications of the directions of different signals (systems in which the directions of different signals are determined sequentially and displayed simultaneously G01S3/04, G01S3/14)
- Y02D 30/70: in wireless communication networks
- 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
- Y02D: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE

## Abstract

A method of sparse array oriented approach for DOA estimation of grating lobe target filtering includes sub-array division processing of received echoes in multiple channels; digital beamforming is performed on each sub-array obtained after division to realize DOA estimation; the echo power of the beam pointing at each angle is calculated and the peak point is detected; peak threshold discrimination processing is performed based on the determined peak threshold; if the current sub-array satisfies the identified peak threshold, the corresponding power spectrum extreme is calculated to obtain the final DOA estimation. The present invention also relates to a corresponding device, processor and computer-readable storage medium thereof. With the use of this sparse array oriented method, device, processor and computer-readable storage medium for implementing filtered DOA estimation of a gate lobe target, the interference of the gate target is effectively avoided by dividing the subarray and binarizing the angular power spectrum.

## Claims

### Claim 1

A method of sparse array oriented approach for Direction Of Arrival (DOA) estimation of grating lobe target filtering for a radio signal received by an array antenna with a sparse layout, comprising following steps:
(1) receiving echoes of the radio signal in multiple channels by the array antenna and dividing, by a processor, the received echoes into a plurality of sub-arrays;
(2) performing, by the processor, digital beam formation on each sub-array obtained after the division to realize DOA estimation;
(3) calculating, by the processor, an echo power of a beam pointing at each angle and determining a peak point from the calculated echo power;
(4) determining a peak threshold discrimination based on the determined peak threshold;
(5) if a current sub-array satisfies the determined peak threshold, then calculating a corresponding power spectrum extreme to obtain a final DOA estimation;
wherein said step (1) specifically comprises:
(1.1) forming, as a unit of row, the sub-array division in an azimuthal dimension;
(1.2) modeling the received echoes of each array element and calculating the echoes of each channel using the following equations:
S
r
=
[
S
r
1
⁢
S
r
2
⁢
…
⁢
S
rN
]
where the Srn denotes each receiving channel echo, (n=1, 2 . . . N), and the N is the number of receiving channels;
(1.3) processing the received echoes in each channel for wave path-difference cancellation and performing phase compensation by using a steering vector for the digital beam formation, where a two-dimensional guiding vector is expressed using the following equation:
α(θ, φ)=[1, e−j2πϕ1(θ, φ), . . . , e−j2πϕN(θ, φ)]
where ϕn(θ, φ) denotes a phase difference between the nth channel and a reference channel, (n=1, 2 . . . N), the phase difference also includes azimuthal phase difference ϕnazim and pitch phase difference ϕnelev, as follows:
ϕn(θ, φ)=ϕnelev+ϕnazim
ϕ
n
azim
(
θ
,
φ
)
=
Δ
⁢
d
n
x
⁢
cos
⁢
φ
⁢
sin
⁢
θ
λ
ϕ
n
elev
(
φ
)
=
Δ
⁢
d
n
y
⁢
sin
⁢
φ
λ
where Δdnx denotes an azimuthal distance between the nth channel and the reference channel, Δdny denotes a pitching direction distance between the nth channel and the reference channel, λ denotes the wavelength, θ denotes an azimuth angle, and φ denotes the pitch angle;
(1.4) completing the subarray division process;
wherein said step (3) specifically comprises:
(3.1) multiplying the steering vector by the each channel echoes to obtain the echo power of the digital beam pointing at each angle, as calculated using the following equation:
pi(θ)=αH(θ)SrSrHα(θ)
where i denotes the ith subarray, pi(θ) denotes the power spectrum of the ith sub-array, αH(θ) denotes the steering vector at an azimuthal angle of θ, Sr denotes the echo vector, and SrH is the conjugate transpose of Sr;
(3.2) normalizing and logarithmizing the power spectrum of each sub-array according to the following equation to calculate the angular power spectrum maximum and thus determine the peak threshold thr:
p
i
norm
(
θ
)
=
10
⁢
log
10
⁢
p
i
(
θ
)
max
[
p
i
(
θ
)
]
where pinorm(θ) denotes power spectrum after normalization of the ith sub-array; and
once the normalized power spectrum is complete, determining the peak threshold thr according to ½ of the power maximum;
(3.3) for peak point detection of the normalized spectrogram pinorm(θ) for each sub-array, retaining the power pinorm(θpeak) at all peak points θpeak;
wherein said step (4) specifically comprises:
setting the angular power greater than or equal to said peak threshold thr to 1 and the angular power less than said peak threshold thr to 0, specifically:
p
i
binary
(
θ
)
=
{
1
p
i
norm
(
θ
peak
)
≥
thr
0
p
i
norm
(
θ
peak
)
<
thr
where pibinary(θ)denotes the binary spectrogram of the ith sub-array.

### Claim 2 (depends on 1)

The sparse array oriented approach for DOA estimation of grating lobe target filtering according to claim 1, wherein said step (2) specifically comprises:
(2.1) defining the pitch direction phase difference at this point by the following equation:
ϕnelev(φ)=0
where ϕnelev(θ) denotes the pitch direction phase difference between the nth channel and the reference channel when the target pitch angle is φ;
(2.2) calculating the phase difference between the n channels and the reference channel to accomplish the DOA estimation, using the following equation to calculate the phase difference:
ϕn(θ, φ)=ϕnazim(θ)=ϕn(θ)
where ϕnazim(θ) denotes the azimuthal phase difference between the nth channel and the reference channel when the target azimuth is θ.

### Claim 3 (depends on 1)

The sparse array oriented approach for DOA estimation of grating lobe target filtering according to claim 1, wherein said step (5) comprises:
(5.1) dot-multiplying the binarized power spectrum of each sub-array set to 1 based on the following equation:
p
binary
(
θ
)
=
∏
i
p
i
binary
(
θ
)
where pbinary(θ) denotes the total power spectrum after dot-multiplication of the binarized power spectra of all sub-arrays;
(5.2) selecting the raw power spectrum pinorm(θ) of the sub-array with the highest number of array elements, and multiplying the selected raw power spectrum pinorm(θ) of the sub-array with the binarized power spectrum after dot-multiplied to obtain the target angular position and echo power as:
p(θ)=pinorm(θ)·pbinary(θ)
where p(θ) denotes the final power spectrum;
(5.3) for peak point detection for the final power spectrum p(θ), using θ corresponding to the location of the peak point as the DOA estimation output.

### Claim 4 (depends on 1)

A device of sparse array oriented approach for DOA estimation of grating lobe target filtering for a radio signal received by an array antenna with a sparse layout, the device comprising:
a processor, configured to execute computer-executable instructions; and
a memory, storing one or more computer-executable instructions, wherein when said computer-executable instructions are executed by said processor, the processor is caused to perform the method of sparse array oriented approach for DOA estimation of grating lobe target filtering as claimed in claim 1.

### Claim 5 (depends on 1)

A processor of sparse array oriented approach for DOA estimation of grating lobe target filtering for a radio signal received by an array antenna with a sparse layout, wherein the processor is configured to execute computer-executable instructions, wherein when said processor is configured to execute computer-executable instructions, the processor is caused to perform the method of sparse array oriented approach for DOA estimation of grating lobe target filtering as claimed in claim 1.

### Claim 6 (depends on 1)

A non-transitory computer-readable storage medium, wherein the non-transitory computer-readable storage medium has a computer program stored on it, said computer program is executed by a processor to cause the processor to perform the method of sparse array oriented approach for DOA estimation of grating lobe target filtering as claimed in claim 1.