Separation of AM cochannel signals in an overloaded signal environment
Multiple cochannel AM signals received in an overloaded signal environment may be separated using RF data through a method of iterative projections.
1. A method for processing AM signals, comprising:
receiving RF data in an overloaded signal environment, said received RF data comprising cochannel AM signals received in the same frequency range and at the same time; and
separating each of said cochannel AM signals from other cochannel AM signals of said received RF data;
wherein said separating comprises estimating each of said cochannel AM signals based on said received RF data; and
wherein said separating further comprises:
providing an initial estimate for each of said cochannel AM signals;
providing a first improved estimate for each of said cochannel AM signals based at least in part on said initial estimates for each of said cochannel AM signals and said received RF data; and
providing a second improved estimate for each of said cochannel AM signals based at least in part on said first improved estimates for each of said cochannel AM signals and said received RF data.
2. The method of claim 1 , wherein said cochannel AM signals are transmitted from geographically remote locations; and wherein said method further comprises receiving said RF data comprising said cochannel AM signals transmitted from geographically remote locations.
3. A method for processing AM signals, comprising:
receiving RF data in an overloaded signal environment, said received RF data comprising cochannel AM signals received in the same frequency range and at the same time; and
separating each of said cochannel AM signals from other cochannel AM signals of said received RF data;
wherein said separating comprises estimating each of said cochannel AM signals based on said received RF data; and
wherein said separating further comprises:
i) providing an initial estimate for each of said cochannel AM signals; and
ii) providing at least one additional improved estimate for each of said cochannel AM signals based at least in part on a most recent previous estimates for each of said cochannel AM signals and said received RF data.
4. The method of claim 3 , further comprising repeating step ii) until a specified termination criteria is satisfied.
5. The method of claim 3 , wherein said RF data is received by a single sensor; wherein said step i) comprises providing an initial estimate of (S) of said cochannel AM signals and an initial estimate of (a) representing amplitudes and phases of said cochannel AM signals; and wherein said step ii) comprises providing an improved estimate (Ŝ (k) ) of said cochannel AM signals based at least in part on a most recent previous estimate (Ŝ (k−1) ) of said cochannel AM signals, a most recent previous estimate of (a) representing amplitudes and phases of said cochannel AM signals, and said received RF data (r).
6. The method of claim 5 , wherein said step ii) comprises providing an additional estimate (Ŝ (k) ) of said cochannel AM signals that minimizes the objective function tr{E H E} and satisfies the constraint bound (δ) according to the following relationship:
min
E
tr
{
E
H
E
}
subject
to
r
-
(
E
+
S
^
(
k
-
1
)
)
a
2
=
δ
where
E
=
S
^
(
k
)
-
S
^
(
k
-
1
)
;
7. The method of claim 3 , wherein said overloaded signal environment is created by intentionally broadcasting said cochannel AM signals simultaneously in the same frequency range.
8. The method of claim 7 , wherein one of said cochannel AM signals comprises public service information; and wherein said method further comprises isolating said AM signal comprising said public service information from other cochannel AM signals of said received RF data.
9. The method of claim 7 , wherein said method further comprises selectively isolating a given one of said cochannel AM signals from other cochannel AM signals of said received RF data in response to a command specifying the identity of said given one of said cochannel AM signals.
10. The method of claim 3 , wherein said cochannel AM signals are transmitted from geographically remote locations; and wherein said method further comprises receiving said RF data comprising said cochannel AM signals transmitted from geographically remote locations.
11. A method for transmitting AM signals, comprising providing RF data comprising cochannel AM signals for transmission in the same frequency range and at the same time for reception by a receiver operating in an overloaded signal environment; and providing a receiver configured to separate each of said cochannel AM signals from other cochannel AM signals of said RF data; said receiver comprising:
receive and separation circuitry coupled to receive RF data from at least one sensor operating in an overloaded signal environment, said received RF data comprising cochannel AM signals received in the same frequency range and at the same time; and
wherein said receive and separation circuitry is configured to separate each of said cochannel AM signals from other cochannel AM signals of said received RF data;
wherein said receive and separation circuitry is configured to separate each of said cochannel AM signals from said other cochannel AM signals by estimating each of said cochannel AM signals based on said received RF data; and
wherein said receive and separation circuitry is further configured to;
i) provide an initial estimate for each of said cochannel AM signals; and
ii) provide at least one additional improved estimate for each of said cochannel AM signals based at least in part on a most recent previous estimates for each of said cochannel AM signals and said received RF data.
12. The method of claim 11 , wherein one of said cochannel AM signals comprises public service information; and wherein said receiver is further configured to isolate said AM signal comprising said public service information from other cochannel AM signals of said received RF data.
13. The method of claim 11 , wherein said receiver is further configured to selectively isolate a given one of said cochannel AM signals from other cochannel AM signals of said received RF data in response to a command specifying the identity of said given one of said cochannel AM signals.
14. The method of claim 11 , wherein said method further comprises:
receiving said RF data in an overloaded signal environment, said received RF data comprising said cochannel AM signals received in the same frequency range and at the same time; and
separating each of said cochannel AM signals from other cochannel AM signals of said received RF data:
wherein said separating comprises estimating each of said cochannel AM signals based on said received RF data; and
wherein said separating further comprises:
i) providing an initial estimate for each of said cochannel AM signals; and
ii) providing at least one additional improved estimate for each of said cochannel AM signals based at least in part on a most recent previous estimates for each of said cochannel AM signals and said received RF data.
15. The method of claim 11 , further comprising transmitting said cochannel AM signals from geographically remote locations.
16. A system for communication using an overloaded signal environment, said system comprising:
transmit circuitry configured to provide RF data comprising cochannel AM signals for transmission in the same frequency range and at the same time; and
receive and separation circuitry configured to receive and separate each of said cochannel AM signals from other cochannel AM signals of said RF data, said receive and separation circuitry coupled to receive RF data from at least one sensor operating in an overloaded signal environment, said received RF data comprising cochannel AM signals received in the same frequency range and at the same time; and
wherein said receive and separation circuitry is configured to separate each of said cochannel AM signals from other cochannel AM signals of said received RF data;
wherein said receive and separation circuitry is configured to separate each of said cochannel AM signals from said other cochannel AM signals by estimating each of said cochannel AM signals based on said received RF data; and
wherein said receive and separation circuitry is further configured to;
i) provide an initial estimate for each of said cochannel AM signals; and
ii) provide at least one additional improved estimate for each of said cochannel AM signals based at least in part on a most recent previous estimates for each of said cochannel AM signals and said received RF data.
17. A method for processing AM signals, comprising:
receiving RF data, said received RF data comprising cochannel AM signals; and
separating each of said cochannel AM signals from other cochannel AM signals of said received RF data by:
i) providing an initial estimate of (S) of said cochannel AM signals and an initial estimate of (a) representing amplitudes and phases of said cochannel AM signals,
ii) providing at least one additional improved estimate of (Ŝ (k) )of said cochannel AM signals based at least in part on a most recent previous estimate (Ŝ (k−1) ) of said cochannel AM signals, a most recent previous estimate of (a) representing amplitudes and phases of said cochannel AM signals, and said received RF data (r), and
iii) repeating step ii) until a specified termination criteria is satisfied.
18. The method of claim 17 , wherein said step ii) comprises providing an additional estimate (Ŝ (k) ) of said cochannel AM signals that minimizes the objective function tr{E H E} and satisfies the constraint bound (δ) according to the following relationship:
min
E
tr
{
E
H
E
}
subject
to
r
-
(
E
+
S
^
(
k
-
1
)
)
a
2
=
δ
where
E
=
S
^
(
k
)
-
S
^
(
k
-
1
)
;
19. The method of claim 18 , wherein said step ii) further comprises minimizing the objective function tr{E H E} and satisfying the constraint bound (δ) by:
a) forming the Lagrangian:
min
E
tr
{
E
H
E
}
subject
to
r
-
(
E
+
S
^
(
k
-
1
)
)
a
2
=
δ
where
E
=
S
^
(
k
)
-
S
^
(
k
-
1
)
;
b) then calculating the gradient of the Lagrangian:
f
(
λ
)
=
(
r
-
S
^
(
k
-
1
)
a
)
H
(
r
-
S
^
(
k
-
1
)
a
)
[
1
-
a
H
(
aa
H
+
1
λ
I
)
-
1
a
]
2
-
δ
;
c) then finding the roots of the gradient of the Lagrangian with respect to E);
d) finding the root of ƒ(λ) that minimizes the objective function objective function tr{EHE}, where:
f
(
λ
)
=
(
r
-
S
^
(
k
-
1
)
a
)
H
(
r
-
S
^
(
k
-
1
)
a
)
[
1
-
a
H
(
aa
H
+
1
λ
I
)
-
1
a
]
2
-
δ
;
e) then calculating the projection (E) using the following relationship:
E
=
(
r
-
S
^
(
k
-
1
)
a
)
a
H
(
aa
H
+
1
λ
I
)
-
1
;
f) then calculating the estimate (Ŝ (k) ) of said cochannel AM signals using the following relationship:
E=Ŝ (k) −Ŝ (k−1) ; and
g) then constraining (Ŝ (k) ) to be real.
20. The method of claim 17 , wherein said cochannel AM signals are transmitted from geographically remote locations; and wherein said method further comprises receiving said RF data comprising said cochannel AM signals transmitted from geographically remote locations.
21. An AM signal processing system, comprising:
receive and separation circuitry coupled to receive RF data from at least one sensor operating in an overloaded signal environment, said received RF data comprising cochannel AM signals received in the same frequency range and at the same time; and
wherein said receive and separation circuitry is configured to separate each of said cochannel AM signals from other cochannel AM signals of said received RF data;
wherein said receive and separation circuitry is configured to separate each of said cochannel AM signals from said other cochannel AM signals by estimating each of said cochannel AM signals based on said received RF data; and
wherein said receive and separation circuitry is further configured to:
provide an initial estimate for each of said cochannel AM signals;
provide a first improved estimate for each of said cochannel AM signals based at least in part on said initial estimates for each of said cochannel AM signals and said received RF data; and
provide a second improved estimate for each of said cochannel AM signals based at least in part on said first improved estimates for each of said cochannel AM signals and said received RF data.
22. The system of claim 21 , wherein said receive and separation circuitry is coupled to receive RF data comprising cochannel AM signals transmitted from geographically remote locations; and wherein said receive and separation circuitry is configured to separate each of said cochannel AM signals from other cochannel AM signals that are transmitted from geographically remote locations.
23. An AM signal processing system, comprising:
receive and separation circuitry coupled to receive RF data from at least one sensor operating in an overloaded signal environment, said received RF data comprising cochannel AM signals received in the same frequency range and at the same time; and
wherein said receive and separation circuitry is configured to separate each of said cochannel AM signals from other cochannel AM signals of said received RF data;
wherein said receive and separation circuitry is configured to separate each of said cochannel AM signals from said other cochannel AM signals by estimating each of said cochannel AM signals based on said received RF data; and
wherein said receive and separation circuitry is further configured to:
i) provide an initial estimate for each of said cochannel AM signals; and
ii) provide at least one additional improved estimate for each of said cochannel AM signals based at least in part on a most recent previous estimates for each of said cochannel AM signals and said received RF data.
24. The system of claim 23 , wherein said receive and separation circuitry is further configured to repeat said step ii) until a specified termination criteria is satisfied.
25. The system of claim 23 , wherein said at least one sensor is a single sensor; and wherein said receive and separation circuitry is further configured to:
perform said step i) by providing an initial estimate of (S) of said cochannel AM signals and an initial estimate of (a) representing amplitudes and phases of said cochannel AM signals; and
perform said step ii) by providing an improved estimate (Ŝ (k) ) of said cochannel AM signals based at least in part on a most recent previous estimate (Ŝ (k−1) ) of said cochannel AM signals, a most recent previous estimate of (a) representing amplitudes and phases of said cochannel AM signals, and said received RF data (r).
26. The system of claim 25 , wherein said receive and separation circuitry is further configured to perform said step ii) by providing an additional estimate (Ŝ (k) ) of said cochannel AM signals that minimizes the objective function tr{E H E} and satisfies the constraint bound (δ) according to the following relationship:
min
E
tr
{
E
H
E
}
subject
to
r
-
(
E
+
S
^
(
k
-
1
)
)
a
2
=
δ
where
E
=
S
^
(
k
)
-
S
^
(
k
-
1
)
;
27. The system of claim 23 , wherein one of said cochannel AM signals comprises public service information; and wherein said receive and separation circuitry is further configured to isolate said AM signal comprising said public service information from other cochannel AM signals of said received RF data.
28. The system of claim 23 , wherein said receive and separation circuitry is further configured to selectively isolate a given one of said cochannel AM signals from other cochannel AM signals of said received RF data in response to a command specifying the identity of said given one of said cochannel AM signals.
29. The system of claim 23 , wherein said receive and separation circuitry is coupled to receive RF data comprising cochannel AM signals transmitted from geographically remote locations; and wherein said receive and separation circuitry is configured to separate each of said cochannel AM signals from other cochannel AM signals that are transmitted from geographically remote locations.
30. An AM signal processing system, comprising:
receive and separation circuitry coupled to receive RF data from a single sensor operating in an overloaded signal environment, said received RF data comprising cochannel AM signals; and
wherein said receive and separation circuitry is configured to separate each of said cochannel AM signals from other cochannel AM signals of said received RF data by:
i) providing an initial estimate of (S) of said cochannel AM signals and an initial estimate of (a) representing amplitudes and phases of said cochannel AM signals,
ii) providing at least one additional improved estimate of (Ŝ (k) )of said cochannel AM signals based at least in part on a most recent previous estimate (Ŝ (k−1) ) of said cochannel AM signals, a most recent previous estimate of (a) representing amplitudes and phases of said cochannel AM signals, and received RF data (r), and
iii) repeating step ii) until a specified termination criteria is satisfied.
31. The system of claim 30 , wherein said receive and separation circuitry is further configured to perform step ii) by providing an additional estimate (Ŝ (k) ) of said cochannel AM signals that minimizes the objective function tr{E H E} and satisfies the constraint bound (δ) according to the following relationship:
min
E
tr
{
E
H
E
}
subject
to
r
-
(
E
+
S
^
(
k
-
1
)
)
a
2
=
δ
where
E
=
S
^
(
k
)
-
S
^
(
k
-
1
)
;
32. The system of claim 30 , wherein said receive and separation circuitry is further configured to perform step ii) by minimizing the objective function tr{E H E} and satisfying the constraint bound (δ) by:
a) forming the Lagrangian:
L
(
E
,
λ
)
=
tr
{
E
H
E
}
+
λ
{
[
r
-
(
E
+
S
^
(
k
-
1
)
)
a
]
H
[
r
-
(
E
+
S
^
(
k
-
1
)
)
a
]
-
δ
}
;
b) then calculating the gradient of the Lagrangian:
∇
E
·
L
(
E
,
λ
)
=
E
+
λ
[
(
E
+
S
^
(
k
-
1
)
)
aa
H
-
ra
H
]
;
c) then finding the roots of the gradient of the Lagrangian with respect to E;
d) finding the root of ƒ(λ) that minimizes the objective function objective function tr{E H E}, where:
f
(
λ
)
=
(
r
-
S
^
(
k
-
1
)
a
)
H
(
r
-
S
^
(
k
-
1
)
a
)
[
1
-
a
H
(
aa
H
+
1
λ
I
)
-
1
a
]
2
-
δ
;
e) then calculating the projection (E) using the following relationship:
E
=
(
r
-
S
^
(
k
-
1
)
a
)
a
H
(
aa
H
+
1
λ
I
)
-
1
;
f) then calculating the estimate (Ŝ (k) ) of said cochannel AM signals using the following relationship:
E=Ŝ (k) −Ŝ (k−1) ; and
g) then constraining (Ŝ (k) ) to be real.
33. The system of claim 30 , wherein said receive and separation circuitry is coupled to receive RF data comprising cochannel AM signals transmitted from geographically remote locations; and wherein said receive and separation circuitry is configured to separate each of said cochannel AM signals from other cochannel AM signals that are transmitted from geographically remote locations.