US 2011/0032046 A1 · I/Q Impairment Calibration Using A Spectrum Analyzer

Abstract

A quadrature modulator (QM) may be calibrated by determining total equivalent offsets in the I- and Q-channels, a total equivalent gain imbalance between the I- and Q-channels, and a total equivalent phase skew between the I- and Q-channels. These values may be obtained by taking various scalar measurements of the image to signal ratio (ISR) and carrier to signal ratio (CSR) of the QM, while alternatively altering the system gain imbalance, system phase skew, I-channel offset and Q-channel offset using a respective gain parameter, phase parameter, I-channel offset parameter, and Q-channel parameter. The gain and phase parameters may be defined in terms of the ISR, and the channel offset parameters may be defined in terms of the CSR. The system gain imbalance, system phase skew, and total offset in the channels may then be calculated based on the various ISR and CSR measurements.

Claims35

Dependent claims

A method for calibrating a quadrature modulator (QM), the method comprising:

(a) defining an image to signal ratio (ISR) characteristic of the QM as a function of:
a total equivalent gain imbalance (EGI) between an I-channel (IC) and a Q-channel (QC) of the QM;
and
a total equivalent phase skew (EPS) between the IC and the QC;
(b) setting a baseband offset frequency for the QM;
(c) setting a carrier frequency for the QM;
(d) measuring a current ISR of the QM to obtain a first ISR value;
(e) defining a gain parameter based on the first ISR value;
(f) altering a system gain imbalance of the QM according to the gain parameter;
(g) measuring the current ISR of the QM subsequent to said altering to obtain a second ISR value;
and
(h) obtaining the EGI of the QM from the first ISR value and the second ISR value.

9 more elements

A system comprising:

a quadrature modulation circuit (QMC) comprising an I-channel (IC) and a Q-channel (QC);
and
a control block configured to control operations of the QMC, wherein the control block is configured to:
(a) define an image to signal ratio (ISR) characteristic of the QMC as a function of:
a total equivalent gain imbalance (EGI) between the IC and the QC;
and
a total equivalent phase skew (EPS) between the IC and the QC;
(b) set a baseband offset frequency for the QMC;
(c) set a carrier frequency for the QMC;
(d) receive a measured current ISR of the QMC to obtain a first ISR value;
(e) define a gain parameter based on the first ISR value;
(f) alter a system gain imbalance of the QMC according to the gain parameter;
(g) receive a measured current ISR of the QMC subsequent to said altering to obtain a second ISR value;
and
(h) obtain the EGI of the QMC from the first ISR value and the second ISR value.

12 more elements

A system comprising:

a quadrature modulation circuit (QMC) comprising an I-channel (IC) and a Q-channel (QC);
and
a control block configured to control operations of the QMC, wherein the control block is configured to:
(a) define a carrier to signal ratio (CSR) characteristic of the QMC as a function of a total equivalent offset in the IC (EOI) and a total equivalent offset in the QC (EOQ);
(b) set a baseband offset frequency for the QMC;
(c) set a carrier frequency for the QMC;
(d) receive a measured current CSR of the QMC to obtain a first CSR value;
(e) define an IC offset parameter based on the first CSR value;
(f) alter an IC offset according to the IC offset parameter;
(g) receive a measured current CSR of the QMC subsequent to said altering the IC offset to obtain a second CSR value;
(h) obtain the EOI of the QMC from the first CSR value and the second CSR value.

8 more elements

Dependencies are inferred from the claim text.

I/Q Impairment Calibration Using A Spectrum Analyzer

Life of this patent

I/Q Impairment Calibration Using A Spectrum Analyzer

Life of this patent

Abstract

Claims35