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 method for self-interference cancellation, the method comprising:
sampling an RF transmit signal to create a sampled RF transmit signal;
decomposing the sampled RF transmit signal into an in-phase transmit signal component and a quadrature transmit signal component;
splitting the in-phase transmit signal component into a first-path in-phase (P1I) component and a second-path in-phase (P2I) component;
splitting the quadrature transmit signal component into a first-path quadrature (P1Q) component and a second-path quadrature (P2Q) component;
scaling at least one of the P1I component or the P2I component;
scaling at least one of the P1Q component or the P2Q component;
delaying the P2I component and the P2Q component;
after delaying the P2I component and scaling at least one of the P1I component or the P2I component, generating an in-phase self-interference cancellation signal component based on the P1I component and the P2I component;
after delaying the P2Q component and scaling at least one of the P1Q component or the P2Q component, generating a quadrature self-interference cancellation signal component based on the P1Q component and the P2Q component;
based on the in-phase self-interference cancellation signal component and the quadrature self-interference cancellation signal component, generating a self-interference cancellation signal; and
generating a composite receive signal, comprising combining the self-interference cancellation signal with a receive signal, wherein the composite receive signal contains less self-interference than the receive signal.
2. The method of claim 1 , wherein an in-phase component delay imposed on the P2I component is substantially different from a quadrature component delay imposed on the P2Q component.
3. The method of claim 1 , wherein:
scaling at least one of the P1I component or the P2I component comprises scaling the P1I component and scaling the P2I component; and
scaling at least one of the P1Q component or the P2Q component comprises scaling the P1Q component and scaling the P2Q component.
4. The method of claim 3 , further comprising:
before scaling the P1I component, at a first amplifier, amplifying the P1I component; and
before scaling the P1Q component, at a second amplifier, amplifying the P1Q component.
5. The method of claim 3 , further comprising:
before generating the in-phase self-interference cancellation signal component, splitting a third-path in-phase (P3I) component from one of: the in-phase transmit signal component, the P1I component, and the P2I component;
before generating the quadrature self-interference cancellation signal component, splitting a third-path quadrature (P3Q) component from one of: the quadrature transmit signal component, the P1Q component, and the P2Q component; and
delaying the P3I component and the P3Q component;
wherein:
the in-phase self-interference cancellation signal component is generated based further on the P3I component; and
the quadrature self-interference cancellation signal component is generated based further on the P3Q component.
6. The method of claim 5 , further comprising:
before generating the in-phase self-interference cancellation signal component, scaling the P3I component; and
before generating the quadrature self-interference cancellation signal component, scaling the P3Q component.
7. The method of claim 3 , wherein: “scaling the PuI component comprises, at a first analog vector modulator (AVM), generating a first linear combination of the PuI component and the PiQ component;” scaling the PiQ component comprises, at the first AVM, generating a second linear combination, different from the first linear combination, of the PuI component and the PiQ component; “scaling the P2I component comprises, at a second AVM, generating a third linear combination of the P2I component and the P2Q component; and Page 4 of 9 Ser. No. 17/005,683 Attorney Docket No.: KUMU-P39 -US3*scaling the P2Q component comprises, at the second AVM, generating a fourth linear combination, different from the third linear combination, of the P2I component and the P2Q component.
8. The method of claim 7 , wherein generating the third linear combination comprises:
generating a first product of the P2I component, a first amplitude scaling value, and a cosine of a first phase shift value;
generating a second product of the P2Q component, the first amplitude scaling value, and a negative of the sine of the first phase shift value; and
summing the first and second products, wherein the sum of the first and second products is the third linear combination.
9. The method of claim 8 , wherein delaying the P2I component and the P2Q component comprises, at an active delayer, delaying a first component by a first delay length, wherein the first component is selected from the set consisting of the P2I component and the P2Q component.
10. The method of claim 9 , further comprising:
based on the first phase shift value, selecting the first delay length; and
in response to selecting the first delay length, configuring the active delayer to delay the first component by the first delay length.
11. The method of claim 9 , wherein the active delayer comprises a bank of switchable capacitors.
12. The method of claim 9 , wherein the active delayer comprises an impedance matching network.
13. The method of claim 8 , wherein generating the fourth linear combination comprises:
generating a third product of the P2I component, the first amplitude scaling value, and the sine of the first phase shift value;
generating a fourth product of the P2Q component, the first amplitude scaling value, and the cosine of the first phase shift value; and
summing the third and fourth products, wherein the sum of the third and fourth products is the fourth linear combination.
14. The method of claim 8 , wherein the second AVM comprises a differential attenuator circuit that scales signals by a total scale factor.
15. The method of claim 14 , wherein:
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 method further comprises configuring the set of switches to control the total scale factor.
16. The method of claim 15 , wherein:
a first subset of the set of scaling stages is communicatively coupled between an input and an output of the differential attenuator circuit, wherein the first subset represents a thermometer encoding; and
a second subset of the set of scaling stages is communicatively coupled between the first stage and the output, wherein the second subset represents a binary encoding.
17. The method of claim 16 , wherein configuring the set of switches comprises:
tuning a first element of the first subset periodically over a first period; and
tuning a second element of the second subset periodically over a second period, wherein the first period is substantially equal to an integer multiple of the second period.
18. The method of claim 7 , wherein:
a complex signal represented by the P2I and the P2Q comprises an intended signal and an image signal, wherein the image signal is substantially equal to the product of a real proportionality constant and a complex conjugate of the intended signal;
the method further comprises estimating the real proportionality constant;
the second AVM generates the third and fourth linear combinations based on the real proportionality constant.
19. The method of claim 18 , wherein:
the third linear combination is equal to a sum of:
a product of the P2I component and
C
cos
ϕ
1
+
δ
,
wherein C is a first amplitude scaling value, ϕ is a first phase shift value, and δ is the real proportionality constant; and
a product of the P2Q component and
-
C
sin
ϕ
1
-
δ
;
and
the fourth linear combination is equal to a sum of:
a product of the P2I component and
C
sin
ϕ
1
+
δ
;
and
a product of the P2Q component and
C
cos
ϕ
1
-
δ
.
20. The method of claim 1 , wherein:
decomposing the sampled RF transmit signal is performed by a frequency downconverter;
generating the self-interference cancellation signal is performed by a frequency upconverter; and
generating the composite receive signal is performed in the RF domain.
21. The method of claim 20 , wherein the in-phase transmit signal component and the quadrature transmit signal component are baseband signal components.