Over-the-air test
View Patent ↗A simulated radio channel is shifted with respect to a plurality of antenna elements coupled with an emulator for communicating with a device under test by using different directions for the simulated radio channel in an anechoic chamber.
1. A method of communicating with an electronic device under test through a simulated radio channel of an emulator, the method comprising:
minimizing a cost function of a theoretical spatial cross correlation and a spatial correlation obtained with antenna elements to determine weights associated with the antenna elements, the cost function being minimized with respect to at least one of gain factors associated with the antenna elements and the weights associated with the antenna elements, thereby enabling the simulated radio channel to be electronically rotated around the device under test without moving the antenna elements;
forming, on the basis of the weights, at least one beam of a simulated radio channel with at least two antenna elements; and
shifting the simulated radio channel with respect to a plurality of the antenna elements coupled with the emulator to communicate with the device under test by using different directions for the simulated radio channel in an anechoic chamber.
2. The method of claim 1 further comprising shifting the simulated radio channel by directing at least one beam of at least one antenna element at different directions towards the device under test.
3. The method of claim 1 further comprising shifting the power angular spectrum of the simulated radio channel by less or more than a distance between two antenna elements for changing the direction of a beam by less or more than an angle of the two antenna elements with respect to the electronic device between two successive moments of communication.
4. The method of claim 1 further comprising shifting the power angular spectrum of the simulated radio channel by a distance between two antenna elements for changing the direction of a beam by an angle of the two antenna elements with respect to the electronic device at two successive moments of communication.
5. The method of claim 1 , further comprising:
feeding the simulated radio channel to the plurality of antenna elements for forming at least one beam of a signal of at least one path with at least one antenna element at a first moment;
setting the simulated radio channel to a new position with respect to the plurality of antenna elements; and
feeding the radio channel which has been set to a new position to the plurality of antenna elements for forming the at least one beam with at least one antenna element of a plurality of antenna elements at a second moment.
6. The method of claim 1 , wherein the cost function is represented by the following equation
E
ρ
(
g
1
,
g
2
,
…
,
g
K
)
=
1
M
∑
m
=
1
M
ρ
(
Δ
m
,
φ
0
,
σ
φ
)
-
ρ
~
(
Δ
m
)
2
,
(
8
)
where ρ(Δ m , φ 0 , σ φ ) represents a theoretical spatial cross correlation of antenna element spacing Δ m of the antenna elements, φ 0 represents a nominal angle-of-arrival, σ φ represents an angular spread, {tilde over (ρ)}(Δ m ) represents a spatial cross correlation, Δ m represents d s /λ 0 where d s is a distance between antenna elements in meters and λ 0 is a wavelength of electromagnetic radiation of a radio signal, the theoretical spatial cross correlation for Laplacian shaped PAS (Power Angular Spectrum) being represented by the following equation
ρ
(
Δ
m
,
φ
0
,
σ
φ
)
=
∫
exp
(
-
j
2
π
Δ
m
sin
(
φ
0
+
φ
)
)
1
2
σ
φ
exp
(
2
φ
σ
φ
)
ⅆ
φ
.
(
11
)
7. A testing system to test communication with an electronic device under test through a simulated radio channel of an emulator, the testing system being configured to perform operations comprising:
minimizing a cost function of a theoretical spatial cross correlation and a spatial correlation obtained with antenna elements to determine weights associated with the antenna elements, the cost function being minimized with respect to at least one of gain factors associated with the antenna elements and the weights associated with the antenna elements, thereby enabling the simulated radio channel to be electronically rotated around the device under test without moving the antenna elements;
forming, on the basis of the weights, at least one beam of a simulated radio channel with at least two antenna elements; and
shifting the simulated radio channel with respect to the plurality of the antenna elements coupled with the emulator to communicate with the device under test by using different directions for the simulated radio channel in an anechoic chamber.
8. The testing system of claim 7 , wherein the testing system is configured to direct at least one beam of at least one antenna element at different directions towards the device under test.
9. The testing system of claim 7 , wherein the testing system is configured to shift the power angular spectrum of the simulated radio channel by less or more than a distance between two antenna elements for changing the direction of a beam by less or more than an angle of the two antenna elements with respect to the electronic device between two successive moments of communication.
10. The testing system of claim 7 , wherein the testing system is configured to shift the power angular spectrum of the simulated radio channel by a distance between two antenna elements for changing the direction of a beam by an angle of the two antenna elements with respect to the electronic device at two successive moments of communication.
11. The testing system of claim 7 , wherein the testing system is configured to perform operations comprising:
feeding the simulated radio channel to the plurality of antenna elements coupled to an emulator for forming at least one beam of a signal of at least one path with at least one antenna element at a first moment;
setting the simulated radio channel to a new position with respect to the plurality of antenna elements; and
feeding the radio channel which has been set to a new position to the plurality of antenna elements for forming the at least one beam with at least one antenna element of a plurality of antenna elements at a second moment.
12. The testing system of claim 7 , wherein the cost function is represented by the following equation
E
ρ
(
g
1
,
g
2
,
…
,
g
K
)
=
1
M
∑
m
=
1
M
ρ
(
Δ
m
,
φ
0
,
σ
φ
)
-
ρ
~
(
Δ
m
)
2
,
(
8
)
where ρ(Δ m , φ 0 , σ φ ) represents a theoretical spatial cross correlation of antenna element spacing Δ m of the antenna elements, φ 0 represents a nominal angle-of-arrival, σ φ represents an angular spread, {tilde over (ρ)}(Δ m ) represents a spatial cross correlation, Δ m represents d s /λ 0 where d s is a distance between antenna elements in meters and λ 0 is a wavelength of electromagnetic radiation of a radio signal, the theoretical spatial cross correlation for Laplacian shaped PAS (Power Angular Spectrum) being represented by the following equation
ρ
(
Δ
m
,
φ
0
,
σ
φ
)
=
∫
exp
(
-
j
2
π
Δ
m
sin
(
φ
0
+
φ
)
)
1
2
σ
φ
exp
(
2
φ
σ
φ
)
ⅆ
φ
.
(
11
)
13. An emulator to communicate with an electronic device under test through a simulated radio channel, the emulator being configured to perform operations comprising:
minimizing a cost function of a theoretical spatial cross correlation and a spatial correlation obtained with antenna elements to determine weights of associated with the antenna elements, the cost function being minimized with respect to at least one of gain factors associated with the antenna elements and the weights associated with the antenna elements, thereby enabling the simulated radio channel to be electronically rotated around the device under test without moving the antenna elements;
forming, on the basis of the weights, at least one beam of a simulated radio channel with at least two antenna elements; and
shifting the simulated radio channel with respect to the plurality of the antenna elements coupled with the emulator to communicate with the device under test by using different directions for the simulated radio channel in an anechoic chamber.
14. The emulator of claim 13 , wherein the cost function is represented by the following equation
E
ρ
(
g
1
,
g
2
,
…
,
g
K
)
=
1
M
∑
m
=
1
M
ρ
(
Δ
m
,
φ
0
,
σ
φ
)
-
ρ
~
(
Δ
m
)
2
,
(
8
)
where ρ(Δ m , φ 0 , σ φ ) represents a theoretical spatial cross correlation of antenna element spacing Δ m of the antenna elements, φ 0 represents a nominal angle-of-arrival, σ φ represents an angular spread, {tilde over (ρ)}(Δ m ) represents a spatial cross correlation, Δ m represents d s /λ 0 where d s is a distance between antenna elements in meters and λ 0 is a wavelength of electromagnetic radiation of a radio signal, the theoretical spatial cross correlation for Laplacian shaped PAS (Power Angular Spectrum) being represented by the following equation
ρ
(
Δ
m
,
φ
0
,
σ
φ
)
=
∫
exp
(
-
j
2
π
Δ
m
sin
(
φ
0
+
φ
)
)
1
2
σ
φ
exp
(
2
φ
σ
φ
)
ⅆ
φ
.
(
11
)