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US 2010/0061485 A1Published application
Systems and Methods for DC Offset Correction in a Direct Conversion RF Receiver
AssigneeGeneral Dynamics C4 Systems, Inc.
InventorsWilliam CLARK, Kelly Don ANDERSON, John Paul SHARRIT
Life of this patent
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Abstract
Systems and methods for DC offset correction in analog and digital direct conversion RF receivers. A time derivate and subsequent integration of in-phase and quadrature phase signal path components is performed to effectively remove DC offset from the resultant down converted baseband signal.
Claims19
A direct conversion RF receiver comprising:
- an RF antenna adapted to receive an RF signal;
- a preselect filter adapted to filter the incoming RF signal;
- a low noise amplifier adapted to amplify the received RF signal;
- a local oscillator producing a local oscillation signal having a frequency tuned to that of the received RF signal;
- a first RF mixer along an in-phase channel path adapted to multiply a received radio frequency signal with the local oscillation signal;
- a second RF mixer along a quadrature-phase channel path adapted to multiply the received radio frequency signal with a 90° phase-shifted version of the local oscillation signal;
- a first low pass filter filtering an output of the first mixer thereby outputting a downconverted in-phase signal I, centered at baseband;
- a second low pass filter filtering an output of the second mixer thereby outputting a downconverted quadrature phase signal Q centered at baseband;
- and
- a residual DC correction circuit adapted to perform a time derivative and subsequent integration of the I and Q signals, wherein the time derivative and subsequent integration are performed after analog-to-digital conversion and comprise solving one or more algebraic expressions.
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A method of reducing direct current offset in a direct conversion receiver comprising:
- receiving an RF signal at the receiver;
- subjecting the RF signal to a preselect filtering process;
- splitting the resultant signal into parallel in-phase (I), and quadrature-phase (Q) signal paths;
- demodulating the respective signals on the I and Q signal paths with mixers located on each signal path and connected to a local oscillator;
- filtering the respective results of the demodulation with a low pass filter to yield downconverted I and Q components of the received RF signal;
- taking a time derivative of each of the respective downconverted signals;
- and
- integrating the results of each time derivative, wherein the time derivative and subsequent integration are performed after analog-to-digital conversion and comprise solving one or more algebraic expressions.
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A method of canceling DC offset in an RF receiver having a direct converter for direct down conversion of a received RF signal to a baseband signal, the method comprising:
- taking a time derivative of signals in respective in-phase and quadrature-phase signal paths of the direct converter;
- and
- integrating the results of the derivative to obtain the received signal without any constant offset value, wherein the time derivative and subsequent integration are performed after analog-to-digital conversion and comprise solving one or more algebraic expressions.
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A DC offset reduction block for a direct conversion circuit of an RF receiver comprising:
- circuitry adapted to take a time derivative of respective signals propagating through in-phase and quadrature phase signal paths of the direct conversion circuit;
- and
- circuitry adapted to integrate the results of the differentiation, thereby yielding respective I and Q components devoid of constant offset values, wherein the time derivative and subsequent integration are performed after analog-to-digital conversion and comprise solving one or more algebraic expressions.
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A direct conversion IF converter comprising:
- an intermediate frequency, IF, filter adapted to filter the IF signal;
- an IF amplifier adapted to amplify the IF signal;
- a local oscillator producing a local oscillation signal having a frequency tuned to that of the IF signal;
- a first IF mixer along an in-phase channel path adapted to multiply a received radio frequency signal with the local oscillation signal;
- a second IF mixer along a quadrature-phase channel path adapted to multiply the received radio frequency signal with a 90° phase-shifted version of the local oscillation signal;
- a first low pass filter filtering an output of the first mixer thereby outputting a downconverted in-phase signal I, centered at baseband;
- a second low pass filter filtering an output of the second mixer thereby outputting a downconverted quadrature phase signal Q centered at baseband;
- and
- a residual DC correction circuit adapted to perform a time derivative and subsequent integration of the I and Q signals, wherein the time derivative and subsequent integration are performed after analog-to-digital conversion and comprise solving one or more algebraic expressions.
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Dependencies are inferred from the claim text.