DC offset correction for direct-conversion receiver
View Patent ↗A DC offset correction system for a direct-conversion receiver is disclosed that may include a DC feedback correction servo-loop in signal communication with a baseband section, where the DC feedback correction servo-loop is coupled to both the input and output of the baseband section and an attenuator within the DC feedback correction servo-loop.
1. A DC offset correction system for a direct-conversion receiver that includes a baseband section that has an input and an output, the DC offset correction system comprising:
a DC feedback correction servo-loop in signal communication with the baseband section, wherein the DC feedback correction servo-loop is coupled to both the input and output of the baseband section; and
an attenuator within the DC feedback correction servo-loop capable of generating an attenuation coefficient k fb .
2. The DC offset correction system of claim 1 , wherein the DC feedback correction servo-loop includes:
an integrator circuit in signal communication with the output of the baseband section; and
a combiner circuit in signal communication with the input of the baseband section.
3. The DC offset correction system of claim 2 , wherein the attenuator includes a resistor and a Sallen-Key RC filter.
4. The DC offset correction system of claim 2 , wherein the integrator circuit is a RC filter.
5. The DC offset correction system of claim 2 , wherein the integrator circuit is a non-RC filter.
6. The DC offset correction system of claim 2 , further including a controller in signal communication with the baseband section and the attenuator.
7. The DC offset correction system of claim 6 , wherein the controller generates a control signal that adjusts the attenuation coefficient k fb .
8. The DC offset correction system of claim 6 , wherein the controller generates a control signal that enables the attenuation coefficient k fb to track the gain of the baseband section.
9. The DC offset correction system of claim 2 , wherein the DC feedback correction servo-loop is arranged to operate according to a high-pass transfer function as follows:
V
o
V
i
=
A
ff
s
s
+
A
ff
k
fb
RC
,
where V i is an input voltage into the system, V o is an output voltage of the baseband section, s is a Laplace transform operator, A ff is the forward gain of the baseband section, R is a resistance of the integrator circuit, and C is a capacitance of the integrator circuit.
10. The DC offset correction system of claim 1 , wherein the attenuator includes a resistor and a Sallen-Key RC filter.
11. The DC offset correction system of claim 10 , further including a controller in signal communication with the baseband section and the attenuator.
12. The DC offset correction system of claim 1 , further including a controller in signal communication with the baseband section and the attenuator.
13. A DC offset correction system for a direct-conversion receiver that includes a baseband section that has an input and an output, the DC offset correction system comprising:
a DC feedback correction servo-loop in signal communication with the baseband section, wherein the DC feedback correction servo-loop is coupled to both the input and output of the baseband section; and
means for producing an attenuation coefficient k fb within the DC feedback correction servo-loop, the attenuation means in signal communication with the input of the baseband section.
14. The DC offset correction system of claim 13 , wherein the DC feedback correction servo-loop includes:
a means for integrating a received signal from the output of the baseband section; and
a means for combining an attenuated feedback signal produced by the attenuation means with received signals to the input of the baseband section.
15. The DC offset correction system of claim 14 , wherein the attenuator means includes a resistor and a Sallen-Key RC filter.
16. The DC offset correction system of claim 14 , wherein the means for integrating includes a RC filter.
17. The DC offset correction system of claim 14 , wherein the means for integrating includes a non-RC filter.
18. The DC offset correction system of claim 14 , further including a controller in signal communication with the baseband section and the attenuator means.
19. The DC offset correction system of claim 18 , wherein the controller generates a control signal that adjusts the attenuation coefficient k fb .
20. The DC offset correction system of claim 18 , wherein the controller generates a control signal that enables the attenuation coefficient k fb to track the gain of the baseband section.
21. The DC offset correction system of claim 14 , wherein the DC feedback correction servo-loop is arranged to operate according to a high-pass transfer function as follows:
V
o
V
i
=
A
ff
s
s
+
A
ff
k
fb
RC
,
where V i is an input voltage into the system, V o is an output voltage of the baseband section, s is a Laplace transform operator, A ff is the forward gain of the baseband section, R is a resistance of the integrator means, and C is a capacitance of the integrator means.
22. A method for correcting for DC offset in a direct-conversion receiver that includes a baseband section that has an input and an output utilizing a DC offset correction system, the method comprising:
processing a received baseband output signal from the output of the baseband section to create a processed feedback signal;
attenuating the processed feedback signal with an attenuation coefficient k fb to create an attenuated feedback signal;
transmitting the attenuated feedback signal to the input of the baseband section.
23. The method of claim 22 , wherein processing includes integrating the received baseband output signal with an integrator circuit.
24. The method of claim 23 , wherein the feedback signal is processed in a DC feedback correction servo-loop of the DC offset correction system that is coupled to an input and an output of the baseband section, integrating includes operating an integrator circuit of the DC offset correction system, and the method further includes operating the DC feedback correction servo-loop according to a high-pass transfer function as follows:
V
o
V
i
=
A
ff
s
s
+
A
ff
k
fb
RC
,
where V i is an input voltage into the system, V o is an output voltage of the baseband section, s is a Laplace transform operator, A ff is the forward gain of the baseband section, R is a resistance of the integrator circuit, and C is a capacitance of the integrator circuit.
25. The method of claim 22 , wherein attenuating includes generating the attenuation coefficient k fb utilizing a resistor for a summation with a Sallen-Key RC filter.
26. The method of claim 25 , wherein the attenuation coefficient k fb is implemented by the ratio of a feedback resistor over the resistor in the input path as Sallen-Key RC filter.
27. The method of claim 22 , wherein transmitting includes combining the attenuated feedback signal with an input signal that is being input into the baseband section.
28. The method of claim 22 , further including controlling the attenuating wherein the attenuation coefficient k fb tracks the gain of the baseband section.