US 2017/0074962 A1Published application

Method and apparatus for simple angle of arrival estimation

AssigneeQatar Foundation for Education, Science and Community Development

InventorsAHMED BADAWY, TAMER KHATTAB, DANIELE TRINCHERO, TAREK ELFOULY, AMR MOHAMED

Life of this patent

Estimating the term…

Loading patent…

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, eβd 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)=ΣMwks(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, 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;
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)=ΣMwks(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
Priority: 16 Sep 2015
Published: 16 Mar 2017
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