Mixer impairment correction based on volterra series
Techniques for compensating for signal impairments introduced by a mixer are discussed. One example system employing such techniques can include mixer predistortion circuitry configured to receive signal in-phase (I) and signal quadrature (Q) components of a signal and to generate a mixer predistortion signal based at least in part on the signal I and Q components, wherein the mixer predistortion signal compensates for nonlinearities caused by a mixer that upconverts the signal. Optionally, imbalance correction circuitry to compensate for gain and phase imbalance and/or skew correction circuitry to compensate for gain and phase skew can also be included.
1. A system configured for use in a transmitter, comprising:
baseband circuitry that generates a first signal comprising signal in-phase (I) and signal quadrature (Q) components;
wherein the baseband circuitry comprises a skew correction circuitry to generate a skew correction signal to compensate for a gain and phase skew caused by a mixer circuit, based at least in part on the signal I and Q components of the first signal;
wherein the skew correction signal comprises a skew correction I component and a skew correction Q component, wherein each of the skew correction I component and the skew correction Q component are linear combinations of the signal I component, the signal Q component, and at least one time-delayed signal I component or at least one time-delayed signal Q component, and
wherein the baseband circuitry comprises mixer predistortion circuitry configured to generate a mixer predistortion signal based on a polynomial approximation involving the signal I and Q components.
2. The system of claim 1 , wherein the baseband circuitry comprises mixer predistortion circuitry configured to receive at least one time-delayed signal I component and at least one time-delayed signal Q component, wherein the mixer predistortion circuitry is configured to generate a mixer predistortion signal that compensates for memory effects caused by the mixer circuit.
3. The system of claim 1 , wherein the polynomial approximation comprises one or more odd order terms of at least third order.
4. The system of claim 3 , wherein the one or more odd order terms comprise cross terms between the signal I component and the signal Q component.
5. The system of claim 3 , wherein at least one of the one or more odd order terms of at least third order is based at least in part on at least one time-delayed signal I component or at least one time-delayed signal Q component.
6. The system of claim 1 , wherein the mixer predistortion circuitry is configured to generate the mixer predistortion signal based at least in part on a least squares approximation of at least one of nonlinearities or memory effects caused by the mixer circuit.
7. The system of claim 1 , further comprising imbalance correction circuitry configured to receive the signal I and Q components of the signal and to generate an imbalance correction signal based at least in part on the signal I and Q components, wherein the imbalance correction signal compensates for a gain and phase imbalance caused by the mixer circuit.
8. The system of claim 7 , wherein the imbalance correction signal comprises an imbalance correction I component and an imbalance correction Q component, wherein each of the imbalance correction I component and the imbalance correction Q component are linear combinations of the signal I and Q components.
9. The system of claim 8 , wherein each of the imbalance correction I component and the imbalance correction Q component are linear combinations of the signal I and Q components based on real coefficients.
10. The system of claim 7 , wherein the imbalance correction signal is based at least in part on a least squares approximation of the gain and phase imbalance caused by the mixer.
11. The system of claim 1 , wherein the skew correction circuitry is additionally configured to receive the at least one time-delayed signal I component and the at least one time-delayed signal Q component, wherein the skew correction signal is based at least in part on the at least one time-delayed signal I component and the at least one time-delayed signal Q component.
12. The system of claim 11 , wherein the skew correction signal comprises a skew correction I component and a skew correction Q component, wherein each of the skew correction I component and the skew correction Q component are linear combinations of the signal I component, the signal Q component, the at least one time-delayed signal I component, and the at least one time-delayed signal Q component.
13. The system of claim 12 , wherein each of the skew correction I component and the skew correction Q component are the linear combinations of the signal I component, the signal Q component, the at least one time-delayed signal I component, and the at least one time-delayed signal Q component based on real coefficients.
14. The system of claim 1 , wherein the skew correction signal is based at least in part on a least squares approximation of the gain and phase skew caused by the mixer.
15. A non-transitory machine readable medium comprising instructions that, when executed, cause a machine to:
receive an in-phase (I) component of a signal and a quadrature (Q) component of the signal;
receive at least one time-delayed I component of the signal and at least one time-delayed Q component of the signal;
receive at least one time-delayed I component of the signal and at least one time-delayed Q component of the signal;
generate a skew correction signal that compensates for a gain and phase skew introduced by a mixer that upconverts the signal, wherein the skew correction signal comprises a skew correction I component and a skew correction Q component that are each based on a linear combination of the signal I component, the signal Q component, the at least one time-delayed I component of the signal, and the at least one time-delayed Q component of the signal, and wherein the skew correction signal is based at least in part on a least squares approximation of the gain and phase skew caused by the mixer; and
generate a mixer predistortion signal that compensates for nonlinearities introduced by the mixer.
16. The non-transitory machine readable medium of claim 15 , wherein the mixer predistortion signal compensates for memory effects introduced by the mixer.
17. The non-transitory machine readable medium of claim 15 , wherein the instructions, when executed, further cause the machine to generate an imbalance correction signal that compensates for a gain and phase imbalance introduced by the mixer.
18. The non-transitory machine readable medium of claim 17 , wherein the imbalance correction signal comprises an imbalance correction I component and an imbalance correction Q component that are each based on a linear combination of the signal I component and the signal Q component.