Quadrature gain and phase imbalance correction in a receiver
OwnerRishi Mohindrainventor
Life of this patent
Estimating the term…
Abstract
The present invention offers a low cost, reliable, on chip implementation that takes advantage of circuitry already present in receivers to calibrate and correct for gain and phase errors in a transceiver device. The present invention employs a digital signal processor along with multiple phase shifters and all pass networks to ensure proper levels of quadrature signals within the transceiver. An internally generated double sideband suppressed carrier signal is created to produce the calibration signals used by the digital signal processor.
Claims20
A method for correcting a phase error imbalance between in-phase (I) and quadrature (Q) components of a calibration signal comprising the acts of:
- adjusting a phase angle to determine a peak amplitude for the in-phase component of the calibration signal;
- adjusting the phase angle to determine a peak amplitude for the quadrature component of the calibration signal;
- adjusting the phase angle to set the amplitudes for the in-phase and quadrature components of the calibration signal to be approximately equal at the same time;
- sending a sine wave signal Sin(ωBB.t) through an I and Q branches of a receiver circuit to measure I sin(t) and Q sin(t);
- sending a cosine wave signal Cos(ωBB.t) through the I and Q branches to measure Q cos(t) and I cos(t);
- computing |I sin(t) Q cos(t)−I cos(t) Q sin(t)|=K3 Sin(ΔφBB);
- and
- adjusting a second phase angle (ΔφBB) based on the computation of K3 Sin(ΔφBB) so that the in-phase and quadrature components of the received signal are 90 degrees out of phase.
A communications device for correcting imbalance between in-phase and quadrature components of a signal comprising:
- a quadrature receiver for receiving signals and converting the received signals into in-phase baseband (I) and a quadrature baseband (Q) signals, wherein the quadrature receiver contains amplifiers and filters in both an in-phase signal path and a quadrature signal path;
- and
- a digital signal processor for determining an imbalance in the quadrature receiver between the inphase and quadrature signal paths of a test signal under varying conditions, wherein the digital signal processor sends a sine test signal and a cosine test signal through the in-phase and quadrature paths of the receiver.
A method of controlling a digital signal processor for correcting a phase error imbalance between in-phase and quadrature components of a calibration signal comprising the acts of:
- adjusting a phase angle to set the amplitudes for the in-phase (I) and quadrature (Q) components of the calibration signal to be approximately equal at the same time;
- sending a sine wave signal Sin(ωBB.t) through the I and Q branches to measure I sin(t) and Q sin(t);
- sending a cosine wave signal Cos(ωBB.t) through the I and Q branches to measure Q cos(t) and I cos(t);
- computing |I sin(t) Q cos(t)−I cos(t) Q sin(t)|=K3. Sin(ΔφBB);
- and
- adjusting center frequencies of all-pass networks within the in-phase and quadrature signal paths so that the in-phase and quadrature components of the calibration signal are 90 degrees out of phase.
A radio transceiver comprising:
- a quadrature receiver for receiving signals and converting the received signals into in-phase baseband and a quadrature baseband signals, wherein the quadrature receiver contains mixers, amplifiers and filters in both an in-phase signal path and a quadrature signal path,
- all-pass networks in both the in-phase and quadrature signal paths, and
- a digital signal processor for adjusting the center frequencies of the all-pass networks in order to minimize a phase error between the in-phase and quadrature signals.
Dependencies are inferred from the claim text.