Apparatus and method for adaptive I/Q imbalance compensation

An apparatus comprising:

• a finite impulse response (FIR) filter configured to filter a version of a digital signal to generate a compensation signal, wherein the FIR filter has filter coefficients, wherein the digital signal comprises a digital representation of a demodulated in-phase and quadrature phase component of a radio frequency (RF) signal;
• an adder configured to sum another version of the digital signal and a version of the compensation signal to generate a balanced digital signal that has an improved image rejection ratio versus the digital signal;
• and
• an adaptation step size adaptor configured to vary adaptation step sizes over time for adaptive adjustment of one or more of the filter coefficients such that the one or more filter coefficients are updated based at least partly on a multiplication product of a selected one of a plurality of different step sizes and two or more samples of the balanced digital signal,
• wherein one of the versions of the digital signal or the version of the compensation signal is a complex conjugate of the digital signal or a complex conjugate of the compensation signal, respectively, and the others are not the complex conjugates, wherein the FIR filter and the adder comprise electronic hardware.

An apparatus comprising:

• a finite impulse response (FIR) filter configured to filter a version of a digital signal to generate a compensation signal, wherein the FIR filter has filter coefficients, wherein the digital signal comprises a digital representation of a demodulated in-phase and quadrature phase component of a radio frequency (RF) signal;
• an adder configured to sum another version of the digital signal and a version of the compensation signal to generate a balanced digital signal that has an improved image rejection ratio versus the digital signal;
• and
• an adaptation step size adaptor configured to provide adaptation step sizes for updating the filter coefficients, wherein the adaptation step size adaptor is configured to divide adaptation step sizes for one or more of the filter coefficients by a squared norm of the balanced digital signal,
• wherein one of the versions of the digital signal or the version of the compensation signal is a complex conjugate of the digital signal or a complex conjugate of the compensation signal, respectively, and the others are not the complex conjugates, wherein the FIR filter and the adder comprise electronic hardware.

A method of improving an image rejection ratio of a digital signal having demodulated in-phase and quadrature-phase components of a radio frequency signal, the method comprising:

• filtering a version of the digital signal with a finite impulse response (FIR) filter having filter coefficients to generate a compensation signal, wherein filtering is implemented by hardware or by instructions implemented by a processor;
• generating a complex conjugate of the digital signal or the compensation signal;
• summing another version of the digital signal and a version of the compensation signal to generate a balanced digital signal that has an improved image rejection ratio versus the digital signal, wherein one of the versions of the digital signal and the version of the compensation signal corresponds to a complex conjugate of the digital signal or the compensation signal, respectively, and the others are not the complex conjugates;
• generating a feedback signal by multiplying a correlation of the balanced digital signal with two or more different adaptation step sizes to generate adjustments for the filter coefficients;
• and
• determining the filter coefficients, using the feedback signal.

A method of improving an image rejection ratio of a digital signal having demodulated in-phase and quadrature-phase components of a radio frequency signal, the method comprising:

• filtering a version of the digital signal with a finite impulse response (FIR) filter having filter coefficients to generate a compensation signal, wherein filtering is implemented by hardware or by instructions implemented by a processor;
• generating a complex conjugate of the digital signal or the compensation signal;
• summing another version of the digital signal and a version of the compensation signal to a generate a balanced digital signal that has an improved image rejection ratio versus the digital signal, wherein one of the versions of the digital signal and the version of the compensation signal corresponds to a complex conjugate of the digital signal or the compensation signal, respectively, and the others are not the complex conjugates;
• generating a feedback signal by multiplying a correlation of the balanced digital signal with one or more adaptation step sizes to generate adjustments for the filter coefficients, wherein at least one of the adaptation step sizes is varied over time;
• and
• determining the filter coefficients, using the feedback signal.

A method of improving an image rejection ratio of a digital signal having demodulated in-phase and quadrature-phase components of a radio frequency signal, the method comprising:

• filtering a version of the digital signal with a finite impulse response (FIR) filter having filter coefficients to generate a compensation signal, wherein filtering is implemented by hardware or by instructions implemented by a processor;
• generating a complex conjugate of the digital signal or the compensation signal;
• summing another version of the digital signal and a version of the compensation signal to generate a balanced digital signal that has an improved image rejection ratio versus the digital signal, wherein one of the versions of the digital signal and the version of the compensation signal corresponds to a complex conjugate of the digital signal or the compensation signal, respectively, and the others are not the complex conjugates;
• generating a feedback signal by multiplying a correlation of the balanced digital signal with one or more adaptation step sizes for the filter coefficients, wherein the one or more of the adaptation step sizes is divided by a squared norm of the balanced digital signal;
• and
• determining the filter coefficients, using the feedback signal.