Wideband transceiver for antenna array
Beam measurement values are computed by transforming a signal to a beamspace representation using a beamforming matrix that includes a plurality of columns that define a plurality of beams. A second plurality of beams is selected from the plurality of beams based on a power captured by each beam derived from the computed beam measurement values. For each beam of the second plurality of beams as a first beam, a spatial phase shift component and a temporal delay component is computed based on the fixed spatial angle associated with the first beam and a carrier frequency, a filter is defined using the spatial phase shift component and the temporal delay component, a beam measurement value associated with the first beam from the computed beam measurement values is selected, and the defined filter is applied to the selected beam measurement value to define a filtered value.
1. A method of processing a communication signal, the method comprising:
receiving a signal by a plurality of antennas;
computing, by a processor, a plurality of beam measurement values by transforming the signal received from each antenna of the plurality of antennas to a beamspace representation using a beamforming matrix, wherein the beamforming matrix includes a plurality of columns, wherein each column of the plurality of columns defines a steering vector for a beam that corresponds to a fixed spatial angle relative to a boresight vector extending from the plurality of antennas, wherein the plurality of columns thereby define a plurality of beams;
selecting, by the processor, a second plurality of beams from the defined plurality of beams based on a power captured by each beam of the plurality of beams that is derived from the computed plurality of beam measurement values;
for each beam of the selected second plurality of beams as a first beam,
computing, by the processor, a spatial phase shift component based on the fixed spatial angle defined for the first beam and a carrier frequency;
computing, by the processor, a temporal delay component based on the fixed spatial angle defined for the first beam and the carrier frequency;
defining, by the processor, a filter using the computed spatial phase shift component and the computed temporal delay component;
selecting, by the processor, a beam measurement value associated with the first beam from the computed plurality of beam measurement values; and
applying, by the processor, the defined filter to the selected beam measurement value to define a filtered value; and
combining the defined filtered values to extract information contained in the received signal.
2. The method of claim 1 , wherein the second plurality of beams includes at least three beams.
3. The method of claim 1 , wherein the second plurality of beams are selected using ={iεI(M):σ i 2 ≧γ}, where M is a number of the plurality of antennas, σ i 2 is a channel power captured by an i th beam of the plurality of beams and γ is a pre-defined threshold.
4. The method of claim 1 , wherein the second plurality of beams are selected based on an angle of a transmitter of the signal relative to the boresight vector.
5. The method of claim 1 , wherein the second plurality of beams are selected as Δ ch =Mα|θ o |, where Δ ch is a number of the second plurality of beams, M is a number of the plurality of antennas, α is a fractional bandwidth of the received signal, and
θ
o
=
d
λ
c
sin
(
ϕ
o
)
,
where d is a spatial distance between adjacent antennas of the plurality of antennas, λ c is a wavelength at the carrier frequency, and φ o is an angle of a transmitter of the signal relative to the boresight vector.
6. The method of claim 1 , wherein the spatial phase shift component is computed using e j2πk(θ o −iΔθ) , where k is an antenna index value,
θ
o
=
d
λ
c
sin
(
ϕ
o
)
,
where d is a spatial distance between adjacent antennas of the plurality of antennas, λ c is a wavelength at the carrier frequency, φ o is an angle of a transmitter of the signal relative to the boresight vector, i is a beam index value to the first beam, and Δθ=1/M, where M is a number of the plurality of antennas.
7. The method of claim 6 , wherein the temporal delay component is computed as
τ
k
=
k
θ
o
f
c
,
where f c is the carrier frequency.
8. The method of claim 7 , wherein the filter is defined using
1
M
∑
k
∈
I
(
M
)
ⅇ
j2π
k
(
θ
o
-
i
Δθ
)
W
sin
c
(
W
(
t
+
τ
k
)
)
,
where W is a bandwidth of the signal and t is a time.
9. A receiver comprising:
a plurality of antennas configured to receive a signal; and
a processor configured to
compute a plurality of beam measurement values by transforming the signal received from each antenna of the plurality of antennas to a beamspace representation using a beamforming matrix, wherein the beamforming matrix includes a plurality of columns, wherein each column of the plurality of columns defines a steering vector for a beam that corresponds to a fixed spatial angle relative to a boresight vector extending from the plurality of antennas, wherein the plurality of columns thereby define a plurality of beams;
select a second plurality of beams from the defined plurality of beams based on a power captured by each beam of the plurality of beams that is derived from the computed plurality of beam measurement values;
for each beam of the selected second plurality of beams as a first beam,
compute a spatial phase shift component based on the fixed spatial angle defined for the first beam and a carrier frequency;
compute a temporal delay component based on the fixed spatial angle defined for the first beam and the carrier frequency;
define a filter using the computed spatial phase shift component and the computed temporal delay component;
select a beam measurement value associated with the first beam from the computed plurality of beam measurement values; and
apply the defined filter to the selected beam measurement value to define a filtered value; and
combine the defined filtered values to extract information contained in the received signal.
10. The receiver of claim 9 , wherein the second plurality of beams includes at least three beams.
11. The receiver of claim 9 , wherein the second plurality of beams are selected using ={iεI(M):σ i 2 ≧γ}, where M is a number of the plurality of antennas, σ i 2 is a channel power captured by an i th beam of the plurality of beams and γ is a pre-defined threshold.
12. The receiver of claim 9 , wherein the second plurality of beams are selected based on an angle of a transmitter of the signal relative to the boresight vector.
13. The receiver of claim 9 , wherein the second plurality of beams are selected as Δ ch =Mα|θ o |, where Δ ch is a number of the second plurality of beams, M is a number of the plurality of antennas, α is a fractional bandwidth of the received signal, and
θ
o
=
d
λ
c
sin
(
ϕ
o
)
,
where d is a spatial distance between adjacent antennas of the plurality of antennas, λ c is a wavelength at the carrier frequency, and φ o is an angle of a transmitter of the signal relative to the boresight vector.
14. The receiver of claim 9 , wherein the spatial phase shift component is computed using e j2πk(θ o −iΔθ) , where k is an antenna index value,
θ
o
=
d
λ
c
sin
(
ϕ
o
)
,
where d is a spatial distance between adjacent antennas of the plurality of antennas, λ c is a wavelength at the carrier frequency, φ o is an angle of a transmitter of the signal relative to the boresight vector, i is a beam index value to the first beam, and Δθ=1/M, where M is a number of the plurality of antennas.
15. The receiver of claim 14 , wherein the temporal delay component is computed as
τ
k
=
k
θ
o
f
c
,
where f c is the carrier frequency.
16. The receiver of claim 15 , wherein the filter is defined using
1
M
∑
k
∈
I
(
M
)
ⅇ
j2π
k
(
θ
o
-
i
Δθ
)
W
sin
c
(
W
(
t
+
τ
k
)
)
,
where W is a bandwidth of the signal and t is a time.
17. A transmitter comprising:
a plurality of antennas configured to receive a first signal and to transmit a second signal; and
a processor configured to
compute a plurality of beam measurement values by transforming the first signal to a beamspace representation using a beamforming matrix, wherein the beamforming matrix includes a plurality of columns, wherein each column of the plurality of columns defines a steering vector for a beam that corresponds to a fixed spatial angle relative to a boresight vector extending from the plurality of antennas, wherein the plurality of columns thereby define a plurality of beams;
select a second plurality of beams from the defined plurality of beams based on a power captured by each beam of the plurality of beams that is derived from the computed plurality of beam measurement values;
for each beam of the selected second plurality of beams as a first beam,
compute a spatial phase shift component based on the fixed spatial angle defined for the first beam and a carrier frequency;
compute a temporal delay component based on the fixed spatial angle defined for the first beam and the carrier frequency; and
define a filter using the computed spatial phase shift component and the computed temporal delay component;
filter a transmit signal through each of the defined filters; and
provide the filtered transmit signal to the beamforming matrix as part of forming the second signal.
18. The transmitter of claim 17 , wherein the second plurality of beams are selected as Δ ch =Mα|θ o |, where Δ ch is a number of the second plurality of beams, M is a number of the plurality of antennas, α is a fractional bandwidth of the received signal, and
θ
o
=
d
λ
c
sin
(
ϕ
o
)
,
where d is a spatial distance between adjacent antennas of the plurality of antennas, λ c is a wavelength at the carrier frequency, and φ o is an angle of a transmitter of the signal relative to the boresight vector.
19. The transmitter of claim 17 , wherein the second plurality of beams are selected using ={iεI(M):σ i 2 ≧γ}, where M is a number of the plurality of antennas, σ i 2 is a channel power captured by an i th beam of the plurality of beams and γ is a pre-defined threshold.
20. The transmitter of claim 17 , wherein the beamforming matrix is implemented as a lens, wherein the filtered signal is provided to the lens by radiating the filtered signal from the plurality of antennas.