Systems and methods for DC component recovery in a zero-IF radio receiver
View Patent ↗Methods and systems for recovering a DC component in a zero-IF radio receiver are disclosed that involve receiving a frequency modulated radio frequency broadcast signal, down-converting the frequency modulated radio frequency broadcast signal directly to an original baseband frequency signal, wherein the original baseband frequency signal includes an original DC component, filtering the original baseband signal to obtain a filtered baseband signal, wherein the original DC component is removed, analyzing modulus values of the filtered baseband signal to determine an estimated quantity for the original DC component, and adding the estimated quantity for the original DC component to the filtered baseband signal to compensate for removal of the original DC component such that a reconstructed baseband signal is obtained.
1. A method for DC component recovery in a zero-IF radio receiver comprising the steps of:
receiving a frequency modulated (FM) radio frequency broadcast signal;
down-converting the frequency modulated radio frequency broadcast signal directly to an original baseband frequency signal, wherein the original baseband frequency signal includes an original DC component;
filtering the original baseband signal to obtain a filtered baseband signal, wherein the original DC component is removed;
analyzing modulus values of the filtered baseband signal to determine an estimated quantity for the original DC component; and
adding the estimated quantity for the original DC component to the filtered baseband signal to compensate for removal of the original DC component such that a reconstructed baseband signal is obtained.
2. The method of claim 1 wherein analyzing modulus values of the filtered baseband signal comprises the steps of:
constructing an error function representing the original DC component; and
minimizing the error function to determine the estimated quantity for the original DC component.
3. The method of claim 2 wherein constructing the error function includes collecting a plurality of samples of the filtered baseband signal.
4. The method of claim 3 wherein the error function is
E
=
1
4
N
∑
i
[
y
i
2
-
R
2
]
2
,
wherein x i , i=1 . . . N represents the plurality of filtered baseband signal samples, X represents a DC offset, y i =x i +X represents a plurality of reconstructed baseband signal samples, and R represents a modulus estimation.
5. The method of claim 4 wherein minimizing the error function is based upon setting a gradient of the error function
∇
E
=
[
∂
E
/
∂
X
∂
E
/
∂
R
]
,
and solving to find an estimation of the DC offset.
6. The method of claim 1 wherein filtering the original baseband signal comprises passing the original baseband signal through a DC notch filter.
7. The method of claim 1 wherein filtering the original baseband signal comprises passing the original baseband signal through a high-pass filter.
8. The method of claim 1 , wherein analyzing modulus values of the filtered baseband signal to determine an estimated quantity for the original DC component comprises algebraically solving a system of equations.
9. The method of claim 1 , wherein analyzing modulus values of the filtered baseband signal to determine an estimated quantity for the original DC component comprises generating successive approximations for the original DC component iteratively until a stopping condition is satisfied to determine the estimated quantity for the original DC component.
10. The method of claim 1 further comprising the step of feeding back the estimated DC component to a voltage adder such that a portion of an unwanted DC voltage from a mixer is removed and wherein a DC blocking filter has a minimized stop-band bandwidth.
11. The method of claim 1 , wherein analyzing modulus values of the filtered baseband signal to determine an estimated quantity for the original DC component comprises:
algebraically solving a system of equations to obtain an initial estimated quantity for the original DC component and using this quantity as a starting value; and
starting with the starting value and generating successive approximations for the original DC component iteratively until a stopping condition is satisfied to determine the estimated quantity for the original DC component.
12. A system for DC component recovery in a zero-IF radio receiver, comprising:
a processing system; and
a memory coupled to the processing system, wherein the processing system is configured to perform the steps of:
receiving a frequency modulated (FM) radio frequency broadcast signal;
down-converting the frequency modulated radio frequency broadcast signal directly to an original baseband frequency signal, wherein the original baseband frequency signal includes an original DC component;
filtering the original baseband signal to obtain a filtered baseband signal, wherein the original DC component is removed;
analyzing modulus values of the filtered baseband signal to determine an estimated quantity for the original DC component; and
adding the estimated quantity for the original DC component to the filtered baseband signal to compensate for removal of the original DC component such that a reconstructed baseband signal is obtained.
13. The system of claim 12 wherein analyzing modulus values of the filtered baseband signal comprises the steps of:
constructing an error function representing the original DC component; and
minimizing the error function to determine the estimated quantity for the original DC component.
14. The system of claim 13 wherein constructing the error function includes collecting a plurality of samples of the filtered baseband signal.
15. The system of claim 14 wherein the error function is
E
=
1
4
N
∑
i
[
y
i
2
-
R
2
]
2
,
wherein x i , i=1 . . . N represents the plurality of filtered baseband signal samples, X represents a DC offset, y i =x i +X represents a plurality of reconstructed baseband signal samples, and R represents a modulus estimation.
16. The system of claim 15 wherein minimizing the error function is based upon setting a gradient of the error function
∇
E
=
[
∂
E
/
∂
X
∂
E
/
∂
R
]
,
and solving to find an estimation of the DC offset.
17. The system of claim 12 wherein filtering the original baseband signal comprises passing the original baseband signal through a DC notch filter.
18. The system of claim 12 wherein filtering the original baseband signal comprises passing the original baseband signal through a high-pass filter.
19. The system of claim 12 , wherein analyzing modulus values of the filtered baseband signal to determine an estimated quantity for the original DC component comprises algebraically solving a system of equations.
20. The system of claim 12 , wherein analyzing modulus values of the filtered baseband signal to determine an estimated quantity for the original DC component comprises generating successive approximations for the original DC component iteratively until a stopping condition is satisfied to determine the estimated quantity for the original DC component.
21. The system of claim 12 further comprising the step of feeding back the estimated DC component to a voltage adder such that a portion of an unwanted DC voltage from a mixer is removed and wherein a DC blocking filter has a minimized stop-band bandwidth.
22. The system of claim 12 , wherein analyzing modulus values of the filtered baseband signal to determine an estimated quantity for the original DC component comprises:
algebraically solving a system of equations to obtain an initial estimated quantity for the original DC component and using this quantity as a starting value; and
starting with the starting value and generating successive approximations for the original DC component iteratively until a stopping condition is satisfied to determine the estimated quantity for the original DC component.
23. A processor non-transitory readable medium having instructions thereon adapted to cause a processing system to recover a DC component baseband signal in a zero-IF radio receiver, the instructions configured to cause the processing system to execute a method comprising the steps of:
receiving a frequency modulated radio frequency broadcast signal;
down-converting the frequency modulated radio frequency broadcast signal directly to an original baseband frequency signal, wherein the original baseband frequency signal includes an original DC component;
filtering the original baseband signal to obtain a filtered baseband signal, wherein the original DC component is removed;
analyzing modulus values of the filtered baseband signal to determine an estimated quantity for the original DC component; and
adding the estimated quantity for the original DC component to the filtered baseband signal to compensate for removal of the original DC component such that a reconstructed baseband signal is obtained.
24. The processor readable medium of claim 23 wherein analyzing modulus values of the filtered baseband signal comprises the steps of:
constructing an error function representing the original DC component; and
minimizing the error function to determine the estimated quantity for the original DC component.
25. The processor readable medium of claim 23 wherein filtering the original baseband signal comprises passing the original baseband signal through a DC notch filter.
26. The processor readable medium of claim 25 wherein constructing the error function includes collecting a plurality of samples of the filtered baseband signal.
27. The processor readable medium of claim 26 wherein the error function is
E
=
1
4
N
∑
i
[
y
i
2
-
R
2
]
2
,
wherein x i , i=1 . . . N represents the plurality of filtered baseband signal samples, X represents a DC offset, y i =x i +X represents a plurality of reconstructed baseband signal samples, and R represents a modulus estimation.
28. The processor readable medium of claim 27 wherein minimizing the error function is based upon setting a gradient of the error function
∇
E
=
[
∂
E
/
∂
X
∂
E
/
∂
R
]
,
and solving to find an estimation of the DC offset.
29. The processor readable medium of claim 23 wherein filtering the original baseband signal comprises passing the original baseband signal through a high-pass filter.
30. The processor readable medium of claim 23 , wherein analyzing modulus values of the filtered baseband signal to determine an estimated quantity for the original DC component comprises algebraically solving a system of equations.
31. The processor readable medium of claim 23 , wherein analyzing modulus values of the filtered baseband signal to determine an estimated quantity for the original DC component comprises generating successive approximations for the original DC component iteratively until a stopping condition is satisfied to determine the estimated quantity for the original DC component.
32. The processor readable medium of claim 23 further comprising the step of feeding back the estimated DC component to a voltage adder such that a portion of an unwanted DC voltage from a mixer is removed and wherein a DC blocking filter has a minimized stop-band bandwidth.
33. The processor readable medium of claim 23 , wherein analyzing modulus values of the filtered baseband signal to determine an estimated quantity for the original DC component comprises:
algebraically solving a system of equations to obtain an initial estimated quantity for the original DC component and using this quantity as a starting value; and
starting with the starting value and generating successive approximations for the original DC component iteratively until a stopping condition is satisfied to determine the estimated quantity for the original DC component.
34. A device for DC component recovery in a zero-IF radio receiver, comprising:
a processor, wherein the processor is configured to perform steps comprising:
receiving a frequency modulated (FM) radio frequency broadcast signal;
down-converting the frequency modulated radio frequency broadcast signal directly to an original baseband frequency signal, wherein the original baseband frequency signal includes an original DC component;
filtering the original baseband signal to obtain a filtered baseband signal, wherein the original DC component is removed;
analyzing modulus values of the filtered baseband signal to determine an estimated quantity for the original DC component; and
adding the estimated quantity for the original DC component to the filtered baseband signal to compensate for removal of the original DC component such that a reconstructed baseband signal is obtained.