DUAL-LOOP TRANSMIT NOISE CANCELLATION

• US 20110158346A1
• Filed: 12/30/2009
• Published: 06/30/2011
• Est. Priority Date: 12/30/2009
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Ballantyne, Gary J.
• Granted Patent: US 8,880,010 B2
• Time in Patent Office: Days
• US Class Current: 375/296
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04B 1/525 with means for reducing leakage of transmitter signal into the receiver
• CPC Class Codes: H04J 11/0023 Interference mitigation or co-ordination direct sequence spread spectrum [DSSS] systems H04B1/7097; frequency hopping H04B1/713; allocation criteria for ingress interference avoidance H04L5/0062; frequency allocation criteria for requirements on out-of-channel emissions H04L5/0066; arrangements for removing intersymbol interference or baseband equalisers H04L25/03006; peak power aspects in multicarrier modulation H04L27/2614; power management H04W52/00; traffic scheduling H04W72/54, H04W72/541

Abstract

A transmitter circuit is described. The transmitter circuit includes a first local oscillator that generates a first frequency equal to a duplex frequency. The transmitter circuit also includes a second local oscillator that generates a second frequency equal to a receive frequency. The transmitter circuit further includes a first mixer that combines the first frequency with a first input signal. The transmitter circuit also includes a first feedback loop. The first feedback loop includes a second mixer that combines the second frequency with a transmit signal and a first filter and a first adder that combines an output of the first mixer with an output of the first filter. The transmitter circuit also includes a third local oscillator that generates a third frequency equal to the receive frequency. The transmitter circuit further includes a third mixer that combines the third frequency with an output of the first adder.

Claims

1. A transmitter circuit comprising:

a first local oscillator, wherein the first local oscillator generates a first frequency equal to a duplex frequency;

a second local oscillator, wherein the second local oscillator generates a second frequency equal to a receive frequency;

a first mixer, wherein the first mixer combines the first frequency with a first input signal;

a first feedback loop, wherein the first feedback loop comprises;

a second mixer, wherein the second mixer combines the second frequency with a transmit signal;

a first filter; and

a first adder, wherein the first adder combines an output of the first mixer with an output of the first filter;

a third local oscillator, wherein the third local oscillator generates a third frequency equal to the receive frequency; and

a third mixer, wherein the third mixer combines the third frequency with an output of the first adder.

2. The transmitter circuit of claim 1, further comprising:

a fourth local oscillator, wherein the fourth local oscillator generates a fourth frequency equal to the duplex frequency;

a second feedback loop, wherein the second feedback loop comprises;

the second mixer;

a fourth mixer, wherein the fourth mixer combines the fourth frequency with an output of the second mixer; and

a second adder, wherein the second adder combines an output of the fourth mixer with a second input signal; and

a second filter.

4. The transmitter circuit of claim 1, further comprising a plant, wherein the plant receives an output of the third mixer and outputs the transmit signal.

5. The transmitter circuit of claim 4, wherein the plant comprises an upconverter.

6. The transmitter circuit of claim 4, wherein the plant comprises an amplifier.

7. The transmitter circuit of claim 1, wherein the first feedback loop removes estimated transmit noise from the transmit signal.

8. The transmitter circuit of claim 2, wherein the second feedback loop removes estimated transmit distortion from the transmit signal.

9. The transmitter circuit of claim 2, wherein the output of the second filter is the first input signal.

10. The transmitter circuit of claim 2, further comprising a third adder, wherein the third adder combines the second input signal and an output of the second filter.

11. The transmitter circuit of claim 10, wherein the output of the third adder is the first input signal.

12. The transmitter circuit of claim 1, wherein the first input signal comprises an inphase (I) modulated signal and a quadrature (Q) modulated signal.

13. The transmitter circuit of claim 2, wherein the second input signal comprises an inphase (I) modulated signal and a quadrature (Q) modulated signal.

3. The transmitter circuit of clam 1, wherein the first filter receives an output of the second mixer.

14. A method for noise cancellation in a transmit signal, the method comprising:

estimate transmit noise in the transmit signal that negatively affects a receive signal;

estimate transmit distortion in the transmit signal that negatively affects the fidelity of the transmit signal;

filter estimated transmit noise from the transmit signal;

filter estimated transmit distortion from the transmit signal; and

provide a filtered transmit signal to a duplexer.

15. The method of claim 14, wherein estimating transmit noise and filtering estimated transmit noise comprise:

mixing a first input signal with a duplex frequency generated by a first local oscillator to obtain a first mixed signal;

combining the first mixed signal with a negative feedback signal to obtain a first combined signal;

mixing the first combined signal with a receive frequency generated by a second local oscillator to obtain a second mixed signal;

applying a plant to the second mixed signal to obtain a transmit signal; and

applying a first feedback loop, wherein applying the first feedback loop comprises;

mixing the transmit signal with a receive frequency generated by a third local oscillator to obtain a down-converted transmit signal; and

filtering the down-converted transmit signal using a first filter to obtain the negative feedback signal.

16. The method of claim 15, wherein the plant comprises an upconverter.

17. The method of claim 15, wherein the plant comprises an amplifier.

18. The method of claim 15, wherein estimating transmit distortion and removing transmit distortion comprises applying a second feedback loop, wherein applying the second feedback loop comprises:

mixing the down-converted transmit signal with a duplex frequency generated by a fourth local oscillator to obtain a third mixed signal;

combining a second input signal with the third mixed signal to obtain a second combined signal; and

filtering the second combined signal using a second filter.

19. The method of claim 18, wherein an output of the second filter is the first input signal.

20. The method of claim 18, wherein the second feedback loop further comprises combining an output of the second filter with the second input signal to obtain a third combined signal.

21. The method of claim 20, wherein the third combined signal is the first input signal.

22. The method of claim 15, wherein the first feedback loop removes estimated transmit noise from the transmit signal.

23. The method of claim 18, wherein the second feedback loop removes estimated transmit distortion from the transmit signal.

24. The method of claim 15, wherein the first input signal comprises an inphase (I) modulated signal and a quadrature (Q) modulated signal.

25. The method of claim 18, wherein the second input signal comprises an inphase (I) modulated signal and a quadrature (Q) modulated signal.

26. A wireless device configured for noise cancellation in a transmit signal, comprising:

means for estimating transmit noise in the transmit signal that negatively affects a receive signal;

means for estimating transmit distortion in the transmit signal that negatively affects the fidelity of the transmit signal;

means for filtering estimated transmit noise from the transmit signal;

means for filtering estimated transmit distortion from the transmit signal; and

means for providing a filtered transmit signal to a duplexer.

27. The wireless device of claim 26, wherein the means for estimating transmit noise and the means for filtering estimated transmit noise comprise:

means for mixing a first input signal with a duplex frequency generated by a first local oscillator to obtain a first mixed signal;

means for combining the first mixed signal with a negative feedback signal to obtain a first combined signal;

means for mixing the first combined signal with a receive frequency generated by a second local oscillator to obtain a second mixed signal;

means for applying a plant to the second mixed signal to obtain a transmit signal; and

means for applying a first feedback loop, wherein applying the first feedback loop comprises;

means for mixing the transmit signal with a receive frequency generated by a third local oscillator to obtain a down-converted transmit signal; and

means for filtering the down-converted transmit signal using a first filter to obtain the negative feedback signal.

28. The wireless device of claim 27, wherein the means for estimating transmit distortion and the means for removing transmit distortion comprise means for applying a second feedback loop, wherein the means for applying the second feedback loop comprises:

means for mixing the down-converted transmit signal with a duplex frequency generated by a fourth local oscillator to obtain a third mixed signal;

means for combining a second input signal with the third mixed signal to obtain a second combined signal; and

means for filtering the second combined signal using a second filter.

29. A computer-readable medium encoded with computer-executable instructions, wherein execution of the computer-executable instructions is for:

estimating transmit noise in the transmit signal that negatively affects a receive signal;

estimating transmit distortion in the transmit signal that negatively affects the fidelity of the transmit signal;

filtering estimated transmit noise from the transmit signal;

filtering estimated transmit distortion from the transmit signal; and

providing a filtered transmit signal to a duplexer.

30. The computer-readable medium of claim 29, wherein the instructions for estimating transmit noise and for filtering estimated transmit noise are further executable for:

mixing a first input signal with a duplex frequency generated by a first local oscillator to obtain a first mixed signal;

combining the first mixed signal with a negative feedback signal to obtain a first combined signal;

mixing the first combined signal with a receive frequency generated by a second local oscillator to obtain a second mixed signal;

applying a plant to the second mixed signal to obtain a transmit signal; and

applying a first feedback loop, wherein applying the first feedback loop comprises;

mixing the transmit signal with a receive frequency generated by a third local oscillator to obtain a down-converted transmit signal; and

filtering the down-converted transmit signal using a first filter to obtain the negative feedback signal.

31. The computer-readable medium of claim 30, wherein the instructions for estimating transmit distortion and for removing transmit distortion comprises instructions for applying a second feedback loop, wherein the instructions for applying the second feedback loop are executable for:

mixing the down-converted transmit signal with a duplex frequency generated by a fourth local oscillator to obtain a third mixed signal;

combining a second input signal with the third mixed signal to obtain a second combined signal; and

filtering the second combined signal using a second filter.