Method and apparatus for performing DC offset cancellation in a receiver
First Claim
1. A method for suppressing DC offset within a baseband signal in a receiver, comprising:
- receiving a baseband signal having a DC offset;
generating a first amplified signal using said baseband signal;
generating a second amplified signal using said baseband signal, said second amplified signal having reduced high frequency content compared to said first amplified signal; and
subtracting said second amplified signal from said first amplified signal to generate an output baseband signal having reduced DC offset.
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Abstract
An amplification system for reducing DC offset in an input signal uses a low pass filter to isolate a DC component of the input signal. The system then subtracts the DC component from the input signal. In one embodiment, the system includes first and second amplifiers in addition to the low pass filter. The first amplifier amplifies the input signal to generate a first amplified signal at a differential output port of the amplification system. The second amplifier amplifies a low pass filtered version of the input signal to generate a second amplified signal at the differential output port of the amplification system. The outputs of the first and second amplifiers are connected to the differential output port of the amplification system in such a way that the first and second signals combine 180 degrees out of phase at the output port. An automatic gain control circuit is also provided that automatically adjusts the gain of the amplification system without changing a bias level associated with the first and second amplifiers.
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Citations
21 Claims
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1. A method for suppressing DC offset within a baseband signal in a receiver, comprising:
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receiving a baseband signal having a DC offset;
generating a first amplified signal using said baseband signal;
generating a second amplified signal using said baseband signal, said second amplified signal having reduced high frequency content compared to said first amplified signal; and
subtracting said second amplified signal from said first amplified signal to generate an output baseband signal having reduced DC offset. - View Dependent Claims (2, 3, 4, 5)
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6. An amplification system to reduce DC offset in a signal, comprising:
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first and second differential input terminals;
first and second differential output terminals;
a first amplifier, coupled to said first and second differential input terminals and said first and second differential output terminals, to amplify a signal received at said first and second differential input terminals to generate a first amplified signal at said first and second differential output terminals;
a low pass filter (LPF) coupled to said first and second differential input terminals, said LPF to filter said signal received at said first and second differential input terminals to generate a filtered signal at an output port of said LPF, said filtered signal having reduced high frequency content; and
a second amplifier coupled to said output port of said LPF and to said first and second differential output terminals to amplify said filtered signal to generate a second amplified signal at said first and second differential output terminals, said second amplifier being connected to said first and second differential output terminals in a manner that causes said first and second amplified signals to subtract at said first and second differential output terminals. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A receiver comprising:
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a mixer having an RF port, an LO port, and a baseband port, said RF port to receive a communication signal and said LO port to receive a local oscillator signal, said mixer to output a baseband signal at said baseband port that includes information derived from said communication signal, said baseband signal including a DC offset component; and
a baseband amplification subsystem comprising;
first and second differential input terminals coupled to said baseband port of said mixer to receive said baseband signal;
first and second differential output terminals;
a first amplifier, coupled to said first and second differential input terminals and said first and second differential output terminals, to amplify said baseband signal to generate a first amplified signal at said first and second differential output terminals;
a low pass filter (LPF) coupled to said first and second differential input terminals to filter said baseband signal to generate a filtered signal at an output port of said LPF, said filtered signal having reduced high frequency content; and
a second amplifier, coupled to said output port of said LPF and to said first and second differential output terminals, to amplify said filtered signal to generate a second amplified signal at said first and second differential output terminals, said second amplifier being connected to said first and second differential output terminals in a manner that causes said first and second amplified signals to subtract at said first and second differential output terminals;
said baseband amplification subsystem generating an amplified baseband signal having a suppressed DC offset component at said first and second differential output terminals. - View Dependent Claims (17, 18, 19, 20, 21)
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Specification