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US 8,014,444 B1Granted
System and method for DC offset, amplitude and phase imbalance correction for I and Q baseband calibration
AssigneeITT Manufacturing Enterprises, Inc.
InventorAnthony G. Marino
Life of this patent
Estimating the term…
Abstract
An algorithm is provided that computes values for correcting for DC offsets of baseband I and Q signals, compensates for amplitude imbalance between the baseband I and Q signals and compensates for phase imbalance between the baseband I and Q signals. Test signals are injected into the I and Q signal processing paths (either or both of the receiver path and baseband path in a modem). Samples of the I and Q signals produced in the I and Q signal processing paths are generated and analyzed to determine DC offsets of the I and Q signals, amplitude imbalance between the I and Q signals and phase imbalance with respect to a desired orthogonal relationship between the I and Q signals.
Claims17
A method for detecting and correcting for DC offsets, amplitude imbalance and phase imbalance in the in-phase (I) and quadrature-phase (Q) baseband signal processing paths of a communication device, comprising:
- a. injecting an I test signal into the I signal processing path to produce an I signal and a Q test signal into the Q signal processing path to produce a Q signal;
- b. analyzing the I signal and the Q signal to determine their DC offsets and computing I and Q DC offset correction values to correct for the DC offsets of the I signal and Q signal, respectively;
- c. applying the I and Q DC offset correction values in the I and Q signal processing paths, respectively, to produce DC offset corrected I and Q signals;
- d. analyzing the DC offset corrected I and Q signals to determine an amplitude imbalance and computing at least one amplitude compensation factor to compensate for the amplitude imbalance, wherein computing the at least one amplitude imbalance compensation factor comprises determining a maximum value of the DC offset corrected I signal and a maximum value of the DC offset corrected Q signal, determining a ratio between the maximum values of the DC offset corrected I and Q signals, respectively, and computing the at least one amplitude imbalance compensation factor from the ratio;
- e. applying the amplitude imbalance correction factor to at least one of the DC offset corrected I and Q signals to produce DC offset corrected and amplitude compensated I and Q signals, wherein applying comprises applying the at least one amplitude imbalance compensation factor to at least one of the I and Q signal processing paths so that the I and Q signal processing paths produce DC offset corrected and amplitude compensated I and Q signals, respectively, that have substantially the same amplitude;
- f. analyzing the DC offset corrected and amplitude compensated I and Q signals to determine phase imbalance with respect to a desired orthogonal relationship and computing a phase imbalance compensation value to compensate for the phase imbalance;
- and
- g. applying the phase imbalance compensation value to at least one of the DC offset corrected and amplitude compensated I and Q signals to produce orthogonal DC offset corrected and amplitude compensated I and Q signals.
5 more elements
A method for detecting and correcting for DC offsets of in-phase (I) and quadrature-phase (Q) baseband signal processing paths of a modem in a communication device, and for amplitude imbalance and phase imbalance between the I and Q signal processing paths, comprising:
- generating I and Q test signals that are supplied to the I and Q signal processing paths, respectively, that in response produce I and Q signals, respectively;
- generating samples of the I and Q signals, respectively;
- analyzing the samples of the I and Q signals to determine DC offsets of the I and Q signals, amplitude imbalance between the I and Q signals and phase imbalance between the I and Q with respect to a desired orthogonal phase relationship;
- computing I and Q DC offset correction values for correcting the DC offsets of the I and Q signals, at least one amplitude imbalance compensation factor for compensating for the amplitude imbalance between the I and Q signals and at least one phase imbalance compensation value for compensating for the phase imbalance between the I and Q signals, wherein computing the at least one amplitude imbalance compensation factor comprises determining a maximum value of the DC offset corrected I signal and a maximum value of the DC offset corrected Q signal, determining a ratio between the maximum values of the DC offset corrected I and Q signals, respectively, and computing the at least one amplitude imbalance compensation factor from the ratio;
- and
- applying the DC offset correction values to the I and Q signal processing paths, respectively, to produce DC offset corrected I and Q signals, applying the at least one amplitude imbalance compensation factor to at least one of the I and Q signal processing paths and the phase imbalance compensation value to at least one of the I and Q signal processing paths, to produce DC offset corrected, amplitude and phase imbalance compensated I and Q signals, and wherein applying comprises applying the at least one amplitude imbalance compensation factor to at least one of the I and Q signal processing paths so that the I and Q signal processing paths produce DC offset corrected and amplitude compensated I and Q signals, respectively, that have substantially the same amplitude.
3 more elements
A modem for use in a communication device, comprising:
- I and Q signal processing modules;
- a test signal generator that generates I and Q test signals that are supplied to the I and Q signal processing modules which in response produce I and Q signals;
- a calibration computation logic processor that receives as input samples of the I and Q signals and computes DC offsets of the I and Q signals, amplitude imbalance between the I and Q signals and phase imbalance between the I and Q with respect to a desired orthogonal phase relationship, and wherein the calibration computation logic processor generates DC offset correction values for correcting DC offsets of the I and Q signals, respectively, at least one amplitude imbalance compensation factor and at least one phase imbalance compensation value, wherein the calibration computation logic processor determines maximum values of the DC offset corrected I signal and DC offset corrected Q signal, respectively, and computes the at least one amplitude imbalance compensation factor based on a ratio of the maximum values of the DC offset corrected I and Q signals, respectively, and supplies the at least one amplitude imbalance compensation factor to at least one of the first and second correction modules;
- and
- first and second correction modules coupled to the I and Q signal processing modules, respectively, wherein the first and second correction modules correct for DC offsets of the I and Q signals, respectively, and at least one of the first and second correction modules corrects for amplitude imbalance and for phase imbalance between the I and Q signals, wherein at least one of the first and second correction modules applies the amplitude imbalance compensation factor to at least one of the I and Q signal processing paths so that the I and Q signal processing paths produce DC offset corrected and amplitude imbalance compensated I and Q signals, respectively, that have substantially equal amplitudes.
2 more elements
A non-transitory computer readable medium that is encoded with instructions which, when executed by a computer, cause the computer to detect and correct for DC offsets in in-phase (I) and quadrature-phase (Q) baseband signal processing paths in a communication device, and to compensate for amplitude and phase imbalance between the I and Q signal processing paths, by:
- generating I and Q test signals that are supplied to the I and Q signal processing paths, respectively, that in response produce I and Q signals, respectively;
- generating samples of the I and Q signals, respectively;
- analyzing the samples of the I and Q signals to determine DC offsets of the I and Q signals, amplitude imbalance between the I and Q signals and phase imbalance between the I and Q with respect to a desired orthogonal phase relationship, wherein the instructions for analyzing comprise instructions for determining maximum values of the DC offset corrected I and Q signals, respectively, and wherein the instructions for computing comprise instructions for computing the at least one amplitude imbalance compensation factor based on a ratio between the maximum values of the DC offset corrected I and Q signals, respectively;
- computing I and Q DC offset correction values for correcting the DC offsets of the I and Q signals, at least one amplitude imbalance compensation factor for compensating for the amplitude imbalance between the I and Q signals and at least one phase imbalance compensation value for compensating for the phase imbalance between the I and Q signals;
- applying the DC offset correction values to the I and Q signal processing paths, respectively, to produce DC offset corrected I and Q signals;
- and
- applying the at least one amplitude imbalance compensation factor to at least one of the I and Q signal processing paths and the phase imbalance compensation value to at least one of the I and Q signal processing paths, to produce DC offset corrected, amplitude and phase imbalance compensated I and Q signals, wherein the instructions for applying the at least one amplitude imbalance compensation factor comprise instructions for applying the at least one amplitude imbalance compensation factor to at least one of the I and Q signal processing paths so that the I and Q signal processing paths produce DC offset corrected and amplitude imbalance compensated I and Q signals, respectively, that have substantially equal amplitudes.
4 more elements
Dependencies are inferred from the claim text.