Systems and methods for configurable hybrid self-interference cancellation
A system for self-interference cancellation includes a frequency downconverter that decomposes a sampled RF transmit signal into an in-phase transmit signal and a quadrature transmit signal; a first analog vector modulator that scales the transmit signals to generate first scaled transmit signals; a second analog vector modulator that scales delayed transmit signals to generate second scaled transmit signals; a frequency upconverter that recomposes the scaled transmit signals into an RF self-interference cancellation signal; and a receive coupler that that combines the RF self-interference cancellation signal with a RF receive signal to reduce self-interference.
1. A system for self-interference cancellation comprising:
a transmit coupler, communicatively coupled to a radio frequency (RF) transmit signal of a communication system, that samples the RF transmit signal to create a sampled RF transmit signal having an RF carrier frequency;
a first analog-self-interference canceller comprising:
a frequency downconverter that decomposes the sampled RF transmit signal into an in-phase transmit signal component and a quadrature transmit signal component;
a first sampling coupler that splits the in-phase transmit signal component into a first-path in-phase transmit signal component and a second-path in-phase transmit signal component;
a second sampling coupler that splits the quadrature transmit signal component into a first-path quadrature transmit signal component and a second-path quadrature transmit signal component;
a first analog vector modulator that scales the first-path in-phase transmit signal component to generate a first scaled in-phase transmit signal component and scales the first-path quadrature transmit signal component to generate a first scaled quadrature transmit signal component;
a first delayer that delays the second-path in-phase transmit signal component to generate a first delayed in-phase transmit signal component;
a second delayer that delays the second-path quadrature transmit signal component to generate a first delayed quadrature transmit signal component;
a second analog vector modulator that scales the first delayed in-phase transmit signal component to generate a second scaled in-phase transmit signal component and scales the first delayed quadrature transmit signal component to generate a second scaled quadrature transmit signal component;
a first combining coupler that combines the first and second scaled in-phase transmit signal components to generate an in-phase self-interference cancellation signal component;
a second combining coupler that combines the first and second scaled quadrature transmit signal components to generate a quadrature self-interference cancellation signal component; and
a frequency upconverter that generates an RF self-interference cancellation signal from the in-phase self-interference cancellation signal component and the quadrature self-interference cancellation signal component; and
a receive coupler, communicatively coupled to an RF receive signal of the communication system, that combines the RF self-interference cancellation signal with the RF receive signal, resulting in an RF composite receive signal; wherein the RF composite receive signal contains less self-interference than the RF receive signal.
2. The system of claim 1 , wherein the first analog-self-interference canceller further comprises:
a third sampling coupler that splits the first delayed in-phase transmit signal component into a first-path first delayed in-phase transmit signal component and a second-path first delayed in-phase transmit signal component; wherein the second analog vector modulator is coupled to the first-path first delayed in-phase transmit signal component;
a fourth sampling coupler that splits the first delayed quadrature transmit signal component into a first-path first delayed quadrature transmit signal component and a second-path first delayed quadrature transmit signal component; wherein the second analog vector modulator is coupled to the first-path first delayed quadrature transmit signal component;
a third delayer that delays the second-path first delayed in-phase transmit signal component to generate a second delayed in-phase transmit signal component;
a fourth delayer that delays the second-path first delayed quadrature transmit signal component to generate a second delayed quadrature transmit signal component; and
a third analog vector modulator that scales the second delayed in-phase transmit signal component to generate a third scaled in-phase transmit signal component and scales the second delayed quadrature transmit signal component to generate a third scaled quadrature transmit signal component;
wherein the first combining coupler combines the first, second, and third scaled in-phase transmit signal components to generate the in-phase self-interference cancellation signal component; wherein the second combining coupler combines the first, second, and third scaled quadrature transmit signal components to generate the quadrature self-interference cancellation signal component.
3. The system of claim 2 , further comprising a first amplifier that amplifies the first-path in-phase transmit signal component prior to scaling by the first analog vector modulator and a second amplifier that amplifies the first-path quadrature transmit signal component prior to scaling by the first analog vector modulator.
4. The system of claim 3 , further comprising a third amplifier that amplifies the RF self-interference cancellation signal prior to combination with the RF receive signal.
5. The system of claim 2 , wherein the in-phase transmit signal component and the quadrature transmit signal component both have an intermediate frequency (IF) carrier frequency; wherein the IF carrier frequency is less than the RF carrier frequency.
6. The system of claim 5 , wherein the IF carrier frequency is 0 Hertz.
7. The system of claim 2 , wherein the first combining coupler comprises a first amplification stage and a second amplification stage; wherein, in a first operating mode, the first combining coupler amplifies the third scaled in-phase transmit signal component using both of the first amplification stage and the second amplification stage; wherein, in the first operating mode, the first combining coupler amplifies the second scaled in-phase transmit signal component using both of the first amplification stage and the second amplification stage; wherein, in the first operating mode, the first combining coupler amplifies the first scaled in-phase transmit signal component using only one of the first amplification stage and the second amplification stage.
8. The system of claim 7 , wherein the first combining coupler further comprises a switch; wherein, in a second operating mode, the first combining coupler amplifies the third scaled in-phase transmit signal component using both of the first amplification stage and the second amplification stage; wherein, in the second operating mode, the first combining coupler amplifies the second scaled in-phase transmit signal component using only one of the first amplification stage and the second amplification stage; wherein, in the second operating mode, the first combining coupler amplifies the first scaled in-phase transmit signal component using only one of the first amplification stage and the second amplification stage; wherein the switch switches the first combining coupler from the first operating mode to the second operating mode.
9. The system of claim 1 , wherein the first analog vector modulator generates the first scaled in-phase transmit signal component from a first linear combination of the first-path in-phase transmit signal component and the first-path quadrature transmit signal component; wherein the first analog vector modulator generates the first scaled quadrature transmit signal component from a second linear combination of the first-path in-phase transmit signal component and the first-path quadrature transmit signal component.
10. The system of claim 9 , wherein to apply a first amplitude scaling value and a first phase shift value, the first analog vector modulator generates the first linear combination by adding a product of the first-path in-phase transmit signal component, the first amplitude scaling value, and a cosine of the first phase shift value to a product of the first-path quadrature transmit signal component, the first amplitude scaling value, and a negative sine of the first phase shift value; and the first analog vector modulator generates the second linear combination by adding a product of the first-path in-phase transmit signal component, the first amplitude scaling value, and a sine of the first phase shift value to a product of the first-path quadrature transmit signal component, the first amplitude scaling value, and a cosine of the first phase shift value.
11. The system of claim 10 , wherein the first analog vector modulator generates the first and second linear combinations using differential attenuator circuits.
12. The system of claim 9 , wherein a complex signal represented by the first-path in-phase transmit signal component and the first-path quadrature transmit signal component contains both of an intended signal and an image signal; wherein the image signal is a complex conjugate of the intended signal.
13. The system of claim 12 , wherein to apply a first amplitude scaling value and a first phase shift value, the first analog vector modulator generates the first and second linear combinations after detecting, measuring, or estimating the image signal; wherein the first analog vector modulator generates the first and second linear combinations to reduce presence of the image signal in the first scaled in-phase transmit signal component and in the first scaled quadrature transmit signal component.
14. The system of claim 13 , wherein to apply a first amplitude scaling value and a first phase shift value, the first analog vector modulator generates the first linear combination by adding a product of the first-path in-phase transmit signal component, the first amplitude scaling value, a cosine of the first phase shift value, and one over a sum of one and a scaling factor to a product of the first-path quadrature transmit signal component, the first amplitude scaling value, a negative sine of the first phase shift value, and one over a difference of one and the scaling factor; and the first analog vector modulator generates the second linear combination by adding a product of the first-path in-phase transmit signal component, the first amplitude scaling value, a sine of the first phase shift value, and one over a sum of one and the scaling factor to a product of the first-path quadrature transmit signal component, the first amplitude scaling value, a cosine of the first phase shift value, and one over a difference of one and the scaling factor.
15. The system of claim 14 , wherein the scaling factor is derived from a signal power ratio of the image signal to the intended signal.
16. The system of claim 15 , wherein the first analog vector modulator generates the first and second linear combinations using differential attenuator circuits.
17. The system of claim 9 , wherein the first analog vector modulator generates the first linear combination by scaling the first-path in-phase transmit signal component using a first differential attenuator circuit, scaling the first-path quadrature transmit signal component using a second differential attenuator circuit, and summing the in-phase transmit signal component and first-path quadrature transmit signal component after scaling; wherein the first analog vector modulator generates the second linear combination by scaling the first-path in-phase transmit signal component using a third differential attenuator circuit, scaling the first-path quadrature transmit signal component using a fourth differential attenuator circuit, and summing the in-phase transmit signal component and first-path quadrature transmit signal component after scaling.
18. The system of claim 17 , wherein the first differential attenuator circuit, having a first set of scaling stages, scales the first-path in-phase transmit signal component by a first total scale factor; wherein the first total scale factor is set by a first state configuration of the first set of scaling stages; wherein the second differential attenuator circuit, having a second set of scaling stages, scales the first-path quadrature transmit signal component by a second total scale factor; wherein the second total scale factor is set by a second state configuration of the second set of scaling stages; wherein the third differential attenuator circuit, having a third set of scaling stages, scales the first-path in-phase transmit signal component by a third total scale factor; wherein the third total scale factor is set by a third state configuration of the third set of scaling stages; wherein the fourth differential attenuator circuit, having a fourth set of scaling stages, scales the first-path quadrature transmit signal component by a fourth total scale factor; wherein the fourth total scale factor is set by a fourth state configuration of the fourth set of scaling stages.
19. The system of claim 18 , wherein the first, second, third, and fourth state configurations are selected from a set of state configurations determined according to a hybrid thermometer code.
20. The system of claim 1 , wherein the first combining coupler comprises a first amplification stage and a second amplification stage; wherein, in a first operating mode, the first combining coupler amplifies the second scaled in-phase transmit signal component using both of the first amplification stage and the second amplification stage; wherein, in the first operating mode, the first combining coupler amplifies the first scaled in-phase transmit signal component using only one of the first amplification stage and the second amplification stage.
21. The system of claim 20 , wherein the first combining coupler further comprises a switch; wherein, in a second operating mode, the first combining coupler amplifies the second scaled in-phase transmit signal component using both of the first amplification stage and the second amplification stage; wherein, in the second operating mode, the first combining coupler amplifies the first scaled in-phase transmit signal component using both of the first amplification stage and the second amplification stage; wherein the switch switches the first combining coupler from the first operating mode to the second operating mode.
22. The system of claim 1 , wherein the first analog vector modulator generates the first scaled in-phase transmit signal component and the first scaled quadrature transmit signal component using a differential attenuator circuit, having a set of scaling stages, that scales signals by a total scale factor; wherein the set of scaling stages is connected to the differential attenuator circuit by a set of switches; wherein the total scale factor is set by a state configuration of the set of switches.
23. The system of claim 22 , wherein the system generates the state configuration by computing a desired scaler output of the differential attenuator circuit and selecting the state configuration resulting in a closest total scale factor to the desired scaler output.
24. The system of claim 23 , wherein the state configuration is selected from a set of state configurations determined according to a hybrid thermometer code.