Virtual beam steering using MIMO radar
View Patent ↗Examples disclosed herein relate to a Multiple-Input Multiple-Output (MIMO) radar for virtual beam steering. The MIMO radar has a plurality of transmit antennas and a receive antenna array having a plurality of radiating elements. The MIMO radar also includes a digital signal processor (DSP) configured to synthesize a virtual receive array having N×M receive subarrays from the plurality of transmit antennas and the receive antenna array, where N is the number of transmit antennas and M is the number of receiving elements. Other examples disclosed herein relate to a method of virtual beam steering.
1. A method of virtual beam steering, comprising:
determining a first manifold matrix from a number of transmit antennas and a physical receive array, wherein the first manifold matrix represents a virtual receive array;
generating a second manifold matrix that represents the virtual receive array with a set of steering angle properties;
determining a transformation matrix from the first manifold matrix and the second manifold matrix;
determining a linear transformation matrix using an optimization criterion that is a function of the first manifold matrix and the transformation matrix applied to the first manifold matrix; and
generating a data set that represents beam steering properties using the determined linear transformation matrix and received signal samples.
2. The method of claim 1 , wherein the first manifold matrix is a function of a geometry of the virtual receive array, a carrier frequency and direction of arrival of signals received from transmit antennas.
3. The method of claim 2 , wherein the virtual beam steering operates to receive signals in a radar system.
4. The method of claim 3 , wherein the first manifold matrix is defined as:
A
=
[
g
11
e
-
j
ω
0
τ
11
…
g
1
N
e
-
j
ω
0
τ
1
N
⋮
⋱
⋮
g
M
1
e
-
j
ω
0
τ
M
1
…
g
MN
e
-
j
ω
0
τ
MN
]
where g ij is channel response between i th transmit antenna to j th receive antenna element, w o is a center frequency, and r is time delay between the i th transmit antenna to the j th receive antenna element, for i=1, 2, . . . , M and j=1, 2, . . . , N, wherein a receive antenna array includes the receive antenna elements.
5. The method as in claim 4 , wherein the time delay σ ij is defined as:
τ
ij
=
1
c
d
ij
sin
(
θ
i
)
where d ij is a distance between the i th element to a reference element, θ i , which is an incident angle between a direction of an incident signal received at the i th element a normal perpendicular to a plane of the virtual receive array.
6. The method as in claim 5 , further comprising digitally processing the incident signal as a radar return signal.
7. The method as in claim 5 , further comprising applying the linear transformation matrix with interpolation to the manifold matrix to generate an oriented virtual subarray within the virtual receive array.
8. The method as in claim 7 , wherein an incident angle is derived from a predetermined direction of arrival for each of the N receive subarrays of the receive virtual array.
9. The method as in claim 5 , further comprising:
applying the linear transformation matrix to a first transmit antenna of the plurality of transmit antennas to determine a second transmit antenna positioned at an angle relative to an original position of the first transmit antenna; and
applying the linear transformation matrix to the receive antenna array to determine a second receive antenna array at an angle relative to an original position of the first receive array.
10. An antenna system, comprising:
a transmit antenna array having N antenna elements;
a receive antenna array having M antenna elements; and
a virtual MIMO engine adapted to generate an NxM virtual receive array as a function operational frequency and angle of arrival of incident signals at the receive antenna array, wherein the virtual MIMO engine comprises a manifold matrix representing the virtual receive array, and a transformation matrix adapted to perform linear transformations on the virtual receive antenna array to steer a virtual beam at a specific angle.
11. The antenna system as in claim 10 , wherein the transmit antenna array has a first transmit subarray and a second transmit subarray, the first transmit subarray associated with a first steering angle.
12. The antenna system as in claim 11 , further comprising a MIMO controller adapted to apply perform linear transformation to the transmit antenna array to determine a second steering angle for the second transmit subarray.
13. The antenna system as in claim 12 , wherein the receive antenna array comprises a first receive subarray and a second receive subarray, and wherein the MIMO controller is adapted to perform linear transformation to the receive antenna array to determine a second receive angle for the second receive subarray.
14. The antenna system as in claim 10 , wherein spacing of the virtual receive antenna array corresponds to spacing of the transmit antenna array.
15. The antenna system as in claim 10 , further comprising a memory storage device for storing a data set representing beam steering properties for linear transformations.
16. A system for a virtual beam steering radar, comprising:
a first controller adapted to:
calculate a first manifold matrix from a number of transmit antennas and a receive antennas, wherein the first manifold matrix represents a virtual receive array;
calculate a second manifold matrix that represents the virtual receive array with a set of steering angle properties;
determine a transformation matrix from the first manifold matrix and the second manifold matrix; and
determine a linear transformation matrix using an optimization criterion that is a function of the first manifold matrix and the transformation matrix applied to the first manifold matrix; and
a memory storage unit storing a data set that represents beam steering properties using the determined linear transformation matrix and received signal samples.
17. The system of claim 16 , wherein the first manifold matrix is a function of a geometry of the virtual receive array, a carrier frequency and direction of arrival of signals received from transmit antennas and the virtual beam steering operates to receive radar reflections.
18. The system of claim 17 , wherein the first manifold matrix is defined as:
A
=
[
g
11
e
-
j
ω
0
τ
11
…
g
1
N
e
-
j
ω
0
τ
1
N
⋮
⋱
⋮
g
M
1
e
-
j
ω
0
τ
M
1
…
g
MN
e
-
j
ω
0
τ
MN
]
where g ij is channel response between i th transmit antenna to j th receive antenna element, w o is a center frequency, and τ ij is time delay between the i th transmit antenna to the j th receive antenna element, for i=1, 2, . . . , M and j=1, 2, . . . , N, wherein a receive antenna array includes the receive antenna elements.
19. The system as in claim 18 , wherein the time delay τ ij is defined as:
τ
ij
=
1
c
d
ij
sin
(
θ
i
)
where d ij is a distance between the i th element to a reference element, θ i , which is an incident angle between a direction of an incident signal received at the i th element a normal perpendicular to a plane of the virtual receive array.
20. The system as in claim 19 , wherein the incident signal is digitally processed as a radar return signal.