Dual-polarization radar processing system using time domain method
Embodiments of the present invention provide for improved estimation of environmental parameters in a dual-polarization radar system. In some embodiments, environmental parameters can be estimated using a linear combination of data received in two orthogonal polarization states. In particular, embodiments of the invention improve ground clutter and noise mitigation in dual polarization radar systems. Moreover, embodiments of the invention also provide for systems to determine the differential reflectivity and/or the magnitude of the co-polar correlation coefficient and the differential phase in a dual polarization radar system.
1. A method comprising:
propagating polarized radar signals to a region of interest using a dual-polarization radar transmitter;
collecting sampled co-polar time series radar data scattered within the region of interest with the dual-polarization radar transmitter, wherein the co-polar time series radar data includes vertically polarized data and horizontally polarized data;
creating, using a computer system, a summed likelihood function by adding a likelihood function for the first time series radar data and a likelihood function for the second time series radar data;
maximizing, using the computer system, the summed likelihood function to estimate the spectral moments of the first time series radar data and the second time series radar data; and
determining, using the computer system, at least one of the differential propagation phase and the co-polar correlation coefficient between the horizontally polarized data and the vertically polarized data from a complex linear combination of the vertically polarized data and horizontally polarized data.
2. The method according to claim 1 , wherein the linear combination of the horizontally polarized data and the vertically polarized data is expressed as V α =V H +αV V .
3. The method according to claim 2 , wherein an optimal value for α for the n th range gate measurement is estimated as
α
opt
(
n
)
=
-
(
Z
^
dr
(
n
)
-
1
)
+
(
Z
^
dr
(
n
)
-
1
)
2
+
4
Re
(
ρ
^
co
(
n
-
1
)
)
Z
^
dr
(
n
)
2
Re
(
ρ
^
co
(
n
-
1
)
)
Z
^
dr
(
n
)
.
4. The method according to claim 2 , wherein an optimal value for α=jβ for the n th range gate measurement is estimated as
β
opt
(
n
)
=
-
(
Z
^
dr
(
n
)
-
1
)
+
(
Z
^
dr
(
n
)
-
1
)
2
+
4
Im
(
ρ
^
co
(
n
-
1
)
)
Z
^
dr
(
n
)
2
Im
(
ρ
^
co
(
n
-
1
)
)
Z
^
dr
(
n
)
.
5. A method of investigating a region of interest with a radar, the method comprising:
propagating polarized radar signals to the region of interest using a dual-polarization radar system;
collecting a first time series radar data scattered within the region of interest with a first polarization using a radar;
collecting a second time series radar data scattered within the region of interest with a second polarization using a radar, wherein the first polarization and the second polarization are substantially orthogonal;
creating, using a computer system, a summed likelihood function by adding a likelihood function for the first time series radar data and a likelihood function for the second time series radar data;
maximizing, using a computer system, the summed likelihood function to estimate the spectral moments of the first time series radar data and the second time series radar data; and
estimating, using a computer system, at least one of the differential propagation phase, the magnitude of the co-polar correlation coefficient, and the phase of the co-polar correlation coefficient using a linear combination of the first time series radar data and the second time series radar data.
6. The method according to claim 5 , wherein at least one of the magnitude of the co-polar correlation coefficient and the phase of the co-polar correlation coefficient are estimated using the first time series radar data and the second time series radar data.
7. The method according to claim 5 , wherein the linear combination of the first time series radar data and the second time series radar data comprises
α
opt
(
n
)
=
-
(
Z
^
dr
(
n
)
-
1
)
+
(
Z
^
dr
(
n
)
-
1
)
2
+
4
Re
(
ρ
^
co
(
n
-
1
)
)
Z
^
dr
(
n
)
2
Re
(
ρ
^
co
(
n
-
1
)
)
Z
^
dr
(
n
)
and
β
opt
(
n
)
=
-
(
Z
^
dr
(
n
)
-
1
)
+
(
Z
^
dr
(
n
)
-
1
)
2
+
4
Im
(
ρ
^
co
(
n
-
1
)
)
Z
^
dr
(
n
)
2
Im
(
ρ
^
co
(
n
-
1
)
)
Z
^
dr
(
n
)
where
α
=
jβ
.
8. The method according to claim 5 , wherein the estimating a magnitude and a phase of the co-polar correlation coefficient includes minimizing a log-likelihood function for the linear combination of the first time series radar data and the second time series radar data.
9. A radar system comprising:
a dual-polarization transmitter configured to transmit a signal in two substantially orthogonal polarizations;
a dual-polarization receiver configured to receive a first signal in first polarization and a second signal in a second polarization, wherein the first polarization and the second polarization are substantially orthogonal;
a computer system coupled at least with the dual polarization receiver, the computer system being configured to:
create a summed likelihood function by adding a likelihood function for the first signal and a likelihood function for the second signal;
maximize the summed likelihood function to estimate the spectral moments of the first signal and the second signal; and,
estimate at least one of the differential propagation phase, the magnitude of the co-polar correlation coefficient, and the phase of the co-polar correlation coefficient using a linear combination of the first signal and the second signal.
10. The radar system according to claim 9 , wherein the computer system is further configured to estimate at least one of the magnitude of the co-polar correlation coefficient and the phase of the co-polar correlation coefficient using the first signal and the second signal.
11. A radar system comprising:
propagation means for propagating radar into a region of interest;
receiving means for receiving radar backscatter in a first polarization state and radar back scatter in a second polarization state from the region of interest; and
computation means for estimating the spectral moments of the radar backscatter in a first polarization state and the radar backscatter in a second polarization state, for minimizing a log-likelihood function of a linear combination of the radar backscatter in the first polarization state and the radar backscatter in the second polarization state, and for estimating at least one of the differential propagation phase, the magnitude of the co-polar correlation coefficient, and the phase of the co-polar correlation coefficient using the minimization of the log-likelihood function of the linear combination of the radar backscatter in the first polarization state and the radar backscatter in the second polarization state.