Method for estimating ambiguous velocity of target
The present application relates to a method for estimating an ambiguous velocity of a target. The method includes: alternately transmitting a first waveform signal and a second waveform signal at a first center frequency and a second center frequency respectively; processing intermediate frequency signals of the first waveform signal and a second waveform signal to generate a first Range-Doppler matrix and a second Range-Doppler matrix respectively; acquiring the quantity of phase convolutions based on a phase difference between the first Range-Doppler matrix and the second Range-Doppler matrix and a beat frequency of the second waveform signal; and estimating a target velocity and a target range through the quantity of phase convolutions. The method has the following beneficial effects; an aliased region and velocity estimation are further improved by using information from a Doppler frequency shift difference, so that the estimation of the ambiguous velocity is more reliable.
1 . A method for estimating an ambiguous velocity of a target, wherein the method is applied to a radar sensor, and comprises:
alternately transmitting a first waveform signal and a second waveform signal at a first center frequency and a second center frequency respectively;
processing intermediate frequency signals of the first waveform signal and the second waveform signal to generate a first Range-Doppler matrix and a second Range-Doppler matrix respectively;
acquiring the quantity of phase convolutions based on a phase difference between the first Range-Doppler matrix and the second Range-Doppler matrix and a beat frequency of the second waveform signal; and
estimating a target velocity and a target range through the quantity of phase convolutions;
after constant false early warning detection and parameter acquisition, the phase between the first Range-Doppler matrix and the second Range-Doppler difference Δφ between the first Range-Doppler matrix and the second Range-Doppler matrix is calculated by the following formula:
Δϕ
=
2
π
[
(
f
c
,
B
-
f
C
,
A
)
2
R
c
+
2
vT
PRI
c
f
c
,
B
]
(
1
)
wherein
ϕ
A
=
2
π
f
C
,
A
2
R
c
,
ϕ
B
=
2
π
[
f
c
,
B
2
R
c
+
2
vT
PRI
c
f
c
,
B
]
,
f
AB
=
f
c
,
B
-
f
c
,
A
,
T
PRI
denotes a sweep frequency period, and
ϕ
1
=
2
π
f
AB
2
R
c
(
2
)
and
ϕ
2
=
2
π
f
DB
T
PRI
(
3
)
are enabled.
2 . The method for estimating an ambiguous velocity of a target according to claim 1 , wherein the first waveform signal and the second waveform signal have the same bandwidth, and the first center frequency is not equal to the second center frequency.
3 . The method for estimating an ambiguous velocity of a target according to claim 1 , wherein the processing intermediate frequency signals of the first waveform signal and the second waveform signal to generate a first Range-Doppler matrix and a second Range-Doppler matrix respectively comprises:
after constructing data matrices for the intermediate frequency signals of the first waveform signal and the intermediate frequency signals of the second waveform signal respectively, obtaining the first Range-Doppler matrix and the second Range-Doppler matrix by two-dimensional Fourier transform processing.
4 . The method for estimating an ambiguous velocity of a target according to claim 1 , wherein the beat frequency of the second waveform signal is calculated by the following formula:
f
beat
,
B
=
2
R
i
c
BW
T
PRI
f
DB
(
4
)
wherein BW denotes the bandwidth, T PRI denotes the sweep frequency period, and f DB denotes a Doppler frequency shift of the second waveform signal, that is,
f
DB
=
2
v
c
f
c
,
B
.
(
15
)
5 . The method for estimating an ambiguous velocity of a target according to claim 4 , wherein phases of the first waveform signal and the second waveform signal have periodicity, and from formula (2), it is obtained that φ 1 is proportional to R, thereby obtaining:
ϕ
1
=
M
·
2
π
+
2
π
f
AB
2
R
Δ
c
(
5
)
wherein
2
π
f
AB
2
R
Δ
c
wherein
2
π
f
AB
2
R
Δ
c
denotes a phase of φ 1 convoluted into [−π, π], and M is an integer and calculated by the following formula:
M
≅
round
(
f
beat
,
B
·
T
PRI
BW
1
f
AB
)
;
(
6
)
an actual phase difference Δφ is a 2π period of the corresponding quantity of convolutions of an estimated phase difference Δφ RDM , that is, Δφ=Δφ RDM +M·2π+m·2π, thereby calculating the actual phase difference by the following formula:
Δ
ϕ
RDM
+
M
·
2
π
+
m
i
·
2
π
=
·
2
π
f
AB
2
R
i
c
+
2
π
f
DBi
T
PRI
(
7
)
wherein m i is an integer, with a range of [−m max , . . . , −2,−1,0,1,2,m max ]; and R i and f DBi denote a range and a Doppler frequency shift corresponding to m i .
6 . The method for estimating an ambiguous velocity of a target according to claim 5 , wherein the acquiring the quantity of phase convolutions based on a phase difference between the first Range-Doppler matrix and the second Range-Doppler matrix and a beat frequency of the second waveform signal further comprises the following steps:
acquiring the Doppler frequency shift f DBi and the quantity of convolutions q i corresponding to m i based on the minimum ambiguous Doppler frequency difference;
obtaining a convolution estimated value q est based on a Doppler frequency shift difference; and
obtaining the quantity q of phase convolutions based on q i and q est .
7 . The method for estimating an ambiguous velocity of a target according to claim 6 , wherein the acquiring the Doppler frequency shiftf DBi and the quantity q i of convolutions corresponding to m i based on the minimum ambiguous Doppler frequency difference comprises:
calculating a corresponding aliased Doppler frequency f DB,RD,i through f DBi by the following formula:
f
DB
,
RD
,
i
=
f
DBi
-
2
q
i
f
D
,
m
ax
;
(
8
)
when f DBi exceeds the maximum Doppler frequency, that is, |f DBi |>f D,max , estimating q i by the following formula:
q
i
-
sign
(
f
DBi
)
·
round
(
f
DBi
-
f
D
,
m
ax
2
·
F
D
,
m
ax
)
,
(
9
)
wherein sign(f DBi ) determines q i as a positive number or a negative number, and round refers to rounding; and
by comparing the aliased Doppler frequency f DB,RD,i with an actual aliased Doppler frequency f DB,aliased , when |f DB,RD,i ·−f DB,aliased | is the smallest, acquiring q i and f DBi wherein the actual aliased Doppler frequency f DB,aliased is obtained through the first Range-Doppler matrix and the second Range-Doppler matrix.
8 . The method for estimating an ambiguous velocity of a target according to claim 7 , wherein the obtaining a convolution estimated value q est of the quantity of convolutions based on a Doppler frequency shift difference comprises:
obtaining an estimated velocity based on the Doppler frequency difference between the first waveform signal and the second waveform signal by the following formula:
v
est
=
f
DE
,
aliased
-
f
DAd
,
aliased
2
f
AB
·
c
;
(
10
)
estimating the convolution estimated value q est through the estimated velocity by the following formula:
q
est
=
round
(
av
est
c
f
τ
,
A
-
f
DA
,
aliased
2
F
D
,
m
ax
)
≈
round
(
av
est
c
f
τ
,
A
-
f
DA
,
aliased
2
F
D
,
m
ax
)
.
(
11
)
9 . The method for estimating an ambiguous velocity of a target according to claim 8 , wherein the obtaining the quantity q of phase convolutions based on q i and q est comprises:
finally acquiring the quantity q of phase convolutions through q i , q est and the corresponding velocity and range by an optimization iteration algorithm.
10 . The method for estimating an ambiguous velocity of a target according to claim 9 , wherein the optimization iteration algorithm at least comprises one of likelihood estimation, Bayesian estimation, and statistical entropy.
11 . The method for estimating an ambiguous velocity of a target according to claim 9 , wherein the estimating a target velocity and a target range through the quantity of phase convolutions comprises:
obtaining the aliased Doppler frequency f DB,RD,i by formula (8), and obtaining the target velocity through the aliased Doppler frequency f DB,RD,i and the Doppler frequency shift of the second waveform signal; and
calculating the target range through the beat frequency of the second waveform signal.