Millimeter-wave sourceless receiver
A receiver includes a planar antenna array including at least three antennas. Each antenna simultaneous receives a local oscillator (LO) signal from a near field region and a radio frequency (RF) signal from a far field region. Each antenna is coupled to a respective quasi-optical mixer. Each quasi-optical mixer includes only passive components and outputs a respective intermediate frequency (IF) signal. The receiver includes two six-port demodulators. Each six-port demodulator receives a different pair of IF signals as input and outputs signals representing baseband power of the pair of IF signals. Each six-port demodulator includes only passive components. The receiver also includes a processor to calculate direction of arrival (DoA) for the LO signal and the RF signal using the output from the six-port demodulators.
1. A receiver comprising:
a planar antenna array including at least three antennas, each antenna being configured for simultaneously receiving a local oscillator (LO) signal from a near field region and a radio frequency (RF) signal from a far field region;
each antenna being coupled to a respective quasi-optical mixer, each quasi-optical mixer including only passive components and outputting a respective intermediate frequency (IF) signal;
at least two six-port demodulators, each six-port demodulator receiving a respective different pair of IF signals as input and outputting signals representing baseband power of the respective pair of IF signals, each six-port demodulator including only passive components; and
a processor coupled to receive output from the six-port demodulators, the processor being configured to calculate direction of arrival (DoA) for the LO signal and the RF signal using the output from the six-port demodulators.
2. The receiver of claim 1 , wherein each six-port demodulator comprises:
a correlator portion; and
a power detector portion, wherein the power detector portion is based on zero-biased schottky diode.
3. The receiver of claim 1 , wherein each quasi-optical mixer is a zero-biased schottky diode-based mixer.
4. The receiver of claim 1 , further comprising:
a power divider coupled to receive a IF signal from at least one quasi-optical mixer, the power divider dividing the IF signal into two signals for input into the at least two six-port demodulators.
5. The receiver of claim 1 , wherein the processor is configured to calculate DoA by:
calculating phase differences between the respective pairs of IF signals using the output from the six-port demodulators; and
calculating the DoA of the LO and RF signals using the phase differences.
6. The receiver of claim 1 , wherein the processor is configured to calculate the DoA using the phase differences by solving the equations:
{
ψ
1
,
2
=
2
π
c
(
f
L
(
L
L
tan
φ
-
d
)
2
+
L
L
2
-
f
L
L
L
sin
φ
-
f
R
d
cos
θ
)
ψ
2
,
3
=
2
π
c
(
f
L
(
L
L
tan
φ
+
d
)
2
+
L
L
2
-
f
L
L
L
sin
φ
+
f
R
d
cos
θ
)
where f L and f R are the frequencies of the LO and RF signals respectively, c is the velocity of light, φ and θ are incident angles of the LO and RF signals with reference to a central antenna of the antenna array, d is linear distance between adjacent antennas in the antenna array, L L is perpendicular distance between a source of the LO signal and the antenna array, and ψ 12 and ψ 23 are phase difference between the respective pairs of IF signals.
7. A method for performing direction of arrival (DoA) estimation, the method comprising:
receiving, at a planar antenna array including at least three antennas, a local oscillator (LO) signal from a near field region and a radio frequency (RF) signal from a far field region simultaneously, each antenna being coupled to a respective quasi-optical mixer to output a respective intermediate frequency (IF) signal;
using output signals from at least two six-port demodulators coupled to the quasi-optical mixers, calculate phase differences between respective pairs of IF signals; and
using the phase differences, calculate incident angles of the LO signal and the RF signal.
8. The method of claim 7 , wherein the output signals from the six-port demodulators represent baseband power of the IF signals for calculating the phase differences.
9. The method of claim 7 , wherein calculating the incident angles comprises solving the equations:
{
ψ
1
,
2
=
2
π
c
(
f
L
(
L
L
tan
φ
-
d
)
2
+
L
L
2
-
f
L
L
L
sin
φ
-
f
R
d
cos
θ
)
ψ
2
,
3
=
2
π
c
(
f
L
(
L
L
tan
φ
+
d
)
2
+
L
L
2
-
f
L
L
L
sin
φ
+
f
R
d
cos
θ
)
where f L and f R are the frequencies of the LO and RF signals respectively, c is the velocity of light, φ and θ are incident angles of the LO and RF signals with reference to a central antenna of the antenna array, d is linear distance between adjacent antennas in the antenna array, L L is perpendicular distance between a source of the LO signal and the antenna array, and ψ 12 and ψ 23 are the phase difference between the respective pairs of IF signals.