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 first combining coupler that generates an in-phase self-interference cancellation signal component based on the first scaled in-phase transmit signal component and the first delayed in-phase transmit signal component;
a second combining coupler that generates a quadrature self-interference cancellation signal component based on the first scaled quadrature transmit signal component and the first delayed quadrature transmit 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 at least one of the first and second delayers is an active delayer.
3. The system of claim 2 , wherein:
the first analog-self-interference canceller further comprises a second analog vector modulator that scales the first delayed in-phase transmit signal component and scales the first delayed quadrature transmit signal component;
the first combining coupler receives the first delayed in-phase transmit signal component from the second analog vector modulator; and
the a second combining coupler receives the first delayed quadrature transmit signal component from the second analog vector modulator.
4. The system of claim 3 , wherein the active delayer is configurable to alter a delay length imposed on a signal delayed by the active delayer.
5. The system of claim 4 , wherein the active delayer comprises a bank of switchable capacitors.
6. The system of claim 4 , wherein the delay length is configured based on a phase shift delay imposed by the second analog vector modulator.
7. The system of claim 2 , wherein the active delayer comprises an impedance matching network.
8. The system of claim 1 , wherein the transmit coupler is an active coupler comprising a power amplifier.
9. The system of claim 8 , further comprising a transmitter amplifier communicatively coupled to a transmitter of the communication system, wherein the transmitter amplifier comprises the power amplifier.
10. The system of claim 1 , further comprising:
a first amplifier that amplifies the first-path in-phase transmit signal component and provides the first-path in-phase transmit signal component to the first analog vector modulator; and
a second amplifier that amplifies the first-path quadrature transmit signal component and provides the first-path quadrature transmit signal component to the first analog vector modulator.
11. The system of claim 10 , further comprising a third amplifier that amplifies the RF self-interference cancellation signal prior to combination with the RF receive signal.
12. The system of claim 1 , 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.
13. The system of claim 12 , wherein the IF carrier frequency is o Hertz.
14. 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; and
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.
15. The system of claim 14 , 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;
the image signal is a complex conjugate of the intended signal; and
the first analog vector modulator generates the first and second linear combinations based on a signal power ratio of the image signal to the intended signal.
16. 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 that scales signals by a total scale factor;
the differential attenuator circuit defines a set of scaling stages;
the set of scaling stages is connected to the differential attenuator circuit by a set of switches; and
the total scale factor is set by a state configuration of the set of switches.
17. The system of claim 16 , wherein:
a first stage of the set of scaling stages is tuned periodically over a first period;
a second stage of the set of scaling stages is tuned periodically over a second period, wherein the first period is an integer multiple of the second period;
the first stage is communicatively coupled between an input and an output of the differential attenuator circuit; and
the second stage is communicatively coupled between the first stage and the output.
18. The system of claim 1 , further comprising:
a second transmit coupler, communicatively coupled to a second RF transmit signal of the communication system, that samples the second RF transmit signal to create a sampled second RF transmit signal; and
a second analog-self-interference canceller that generates a second RF self-interference cancellation signal based on the sampled second RF transmit signal;
wherein the receive coupler further combines the second RF self-interference cancellation signal with the RF receive signal to generate the RF composite receive signal.
19. The system of claim 18 , further comprising a second receive coupler communicatively coupled to a second RF receive signal of the communication system, wherein:
the first analog-self-interference canceller generates a third RF self-interference cancellation signal based on the sampled RF transmit signal;
the second analog-self-interference canceller generates a fourth RF self-interference cancellation signal based on the sampled second RF transmit signal; and
the second receive coupler combines the third and fourth RF self-interference cancellation signals with the second RF receive signal, resulting in a second RF composite receive signal; wherein the second RF composite receive signal contains less self-interference than the second RF receive signal.
20. The system of claim 19 , further comprising:
a first switch operable between a first mode, in which the sampled RF transmit signal is coupled to the first analog-self-interference canceller, and a second mode, in which the sampled RF transmit signal is coupled to the second analog-self-interference canceller; and
a second switch operable between a third mode, in which the sampled second RF transmit signal is coupled to the first analog-self-interference canceller, and a fourth mode, in which the sampled second RF transmit signal is coupled to the second analog-self-interference canceller.