US 10,386,447 B2Granted

Method and apparatus for simple angle of arrival estimation

AssigneeQatar University

InventorsAhmed Badawy, Tamer Khattab, Daniele Trinchero, Tarek Elfouly, Amr Mohamed

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Abstract

The method and apparatus for angle of arrival estimation are used for estimating the angle of arrival of a received signal by a switched beam antenna array and a single receiver. The switched beam antenna array first collects an omnidirectional signal to be used as a reference signal. A main beam thereof is then switched to scan an angular region of interest. The collected signals from the switched beams are cross-correlated with the reference signal. The cross-correlation coefficient is the highest at the true angle of arrival and relatively negligible otherwise. The collected signal from each beam angle is cross-correlated with the omnidirectional reference signal to determine the angle of arrival of the received signal.

Claims3

Dependent claims

A method of estimating angle of arrival of a received signal, comprising the steps of:

(a) receiving an omnidirectional signal with a subset of antenna elements of a switched beam antenna array, the switched beam antenna array having M total antenna elements, wherein during reception of the omnidirectional signal, a remainder of the antenna elements are switched off by RF switches;
(b) dividing an angular space of interest into K beams;
(c) setting an integer k equal to 1;
(d) calculating a k-th steering vector, ak(ϕk), which points to a k-th azimuth angle, (ϕk, for the switched beam antenna array as ak(ϕk)=[1, eβd cos ϕk, eβ2d cos ϕk, . . . , eβ(m−1)d cos ϕk], wherein
β
=
2
⁢
π
λ
,
where λ is a wavelength of a signal s(t) received by the switched beam antenna array, and d being a separation distance between adjacent ones of the antenna elements, the switched beam antenna array being a uniform linear antenna array;
(e) calculating a k-th weight vector, wk, wherein, for uniform excitation, the k-th weight vector is calculated as wk=ak(ϕk), and for non-uniform Dolph-Chebyshev excitation, the k-th weight vector is calculated as wk=acejψk, where ψk=βd cos ϕk and ac, are coefficients of dimensions 1×M of an inverse z-transform of an array factor, A (Z), where A(Z)=Z−(M−1)/2Πi=1M−1(Z−Zi), where Zi=2ejφi and
φ
i
=
2
⁢
cos
-
1
⁡
(
y
i
y
0
)
,
where
y
i
=
cos
⁡
(
(
i
-
1
/
2
)
⁢
π
M
-
1
)
for i=1, 2, . . . M−1 and
y
0
=
cosh
⁡
(
cosh
-
1
⁡
(
R
)
M
-
1
)
,
where R is a main lobe to side lobe ratio and j represents the imaginary number;
(f) if k<K, then setting k=k+1 and returning to step (d);
(g) feeding the set of weights wk for all k=1, . . . , K to attenuators and phase shifters of the switched beam antenna array such that a main beam thereof is directed toward the k-th azimuth angle;
(h) collecting a k-th received signal component, xk(n), from a direction of the k-th azimuth angle ϕk for a sample n of N total samples as xk(n)=ΣMwkx(n)+v(n), where v(n) is additive white Gaussian noise;
(i) calculating a cross-correlation coefficient, Rk0, between an n-th sample of a reference signal, x0(n), and the k-th received signal component, xk(n), as
R
k
⁢
⁢
0
=
1
N
⁢
∑
n
=
1
N
⁢
x
k
⁡
(
n
)
⁢
x
0
H
⁡
(
n
)
,
where x0H(n) is a Hermitian of the reference signal x0(n), the received omnidirectional signal being the reference signal;
and
(j) calculating an angle of arrival as an azimuth angle, ϕk*, where k*=argmaxk(Rk0).

103 more elements

An apparatus of estimating angle of arrival of a received signal, comprising:

a switched beam antenna array having M total antenna elements, the switched beam antenna array receiving an omnidirectional signal with a subset of the antenna elements, an angular space of interest being divided into K beams;
a plurality of RF switches in communication with the switched beam antenna array, wherein during reception of the omnidirectional signal, a remainder of the antenna elements are switched off by the RF switches;
means for calculating a k-th steering vector, ak(ϕk), which points to a k-th azimuth angle, ϕk, for the switched beam antenna array as ak(ϕk)=[1, eβd cos ϕk, eβ2d cos ϕk, . . . , eβ(m−1)d cos ϕk],wherein
β
=
2
⁢
π
λ
,
where λ is a wavelength of a signal s(t) received by the switched beam antenna array, and d being a separation distance between adjacent ones of the antenna elements, the switched beam antenna array being a uniform linear antenna array, k being an integer ranging between 1 and K;
means for calculating a k-th weight vector, wk, wherein, for uniform excitation, the k-th weight vector is calculated as [[Wk=acejψk]] wk=ak(ϕk) and for non-uniform Dolph-Chebyshev excitation, the k-th weight vector is calculated as wk=acejψk, where ψk=βd cos (ϕk and ac are coefficients of dimensions 1×M of an inverse z-transform of an array factor, A(Z), where A(Z)=Z−(M−1)/2Πi=1M−1(Z−Zi), where Zi=2ejφi and
φ
i
=
2
⁢
⁢
cos
-
1
⁡
(
y
i
y
0
)
,
where
y
i
=
cos
⁡
(
(
i
-
1
/
2
)
⁢
π
M
-
1
)
where for i=1, 2, . . . , M−1 and
y
0
=
cosh
⁡
(
cosh
-
1
⁡
(
R
)
M
-
1
)
,
where R is a main lobe to side lobe ratio and j represents the imaginary number;
means for feeding the set of weights wk for all k=1, . . . , K to attenuators and phase shifters of the switched beam antenna array such that a main beam thereof is directed toward the k-th azimuth angle;
means for collecting a k-th received signal component, xk(n), from a direction of the k-th azimuth angle ϕk for a sample n of N total samples as xk(n)=ΣMwkx(n)+v(n), where v(n) is additive white Gaussian noise;
means for calculating a cross-correlation coefficient, Rk0, between an n-th sample of a reference signal, x0(n), and the k-th received signal component, xk(n), as
R
k
⁢
⁢
0
=
1
N
⁢
∑
n
=
1
N
⁢
x
k
⁡
(
n
)
⁢
x
0
H
⁡
(
n
)
,
where x0H(n) is a Hermitian of the reference signal x0(n), the received omnidirectional signal being the reference signal;
and
means for calculating an angle of arrival as an azimuth angle, ϕk*, where k*=argmaxk(Rk0).

102 more elements

Dependencies are inferred from the claim text.

Facts

Application: 15/268,371Filed 16 Sep 2016 · us provisional application
Priority: 16 Sep 2015
Published: US 2017/0074962 A116 Mar 2017
Granted: 20 Aug 2019
Term ends: Not estimatedThe source records don’t support an estimate.

Classification3 codes

G01S 3/38
Systems for determining direction or deviation from predetermined direction: using adjustment of real or effective orientation of directivity…
G01S 3/065
Means for increasing effective directivity, e.g. by combining signals having differently oriented directivity characteristics or by sharpening…
G01S
Radio direction-finding