EQUALIZATION OF THIRD-ORDER INTERMODULATION PRODUCTS IN WIDEBAND DIRECT CONVERSION RECEIVER

• US 20090075612A1
• Filed: 09/18/2008
• Published: 03/19/2009
• Est. Priority Date: 09/18/2007
• Status: Active Grant

• Current Assignee: California Institute of Technology
• Original Assignee: California Institute of Technology
• Inventors: Keehr, Edward, Hajimiri, Seyed Ali
• Granted Patent: US 8,290,449 B2
• Time in Patent Office: Days
• US Class Current: 455/226.100
• CPC Class Codes: H03D 7/14 Balanced arrangements
• CPC Class Codes: H04B 1/123 using adaptive balancing or compensation means adaptive filter circuits and algorithms H03H

Abstract

A feedforward error-compensated receiver for minimizing undesired odd-order nonlinear distortion products. The receiver includes a first receiver path configured to receive an input signal. The first receiver path outputs a signal including at least one baseband (BB) frequency. At least one second receiver path is configured to receive the input signal and to provide a second receiver path output signal. The second receiver path includes at least one odd-order nonlinear distortion reference generator. The at least one odd-order nonlinear distortion reference generator and the mixer are configured to generate a synthetic odd-order nonlinear distortion signal. A combining element is configured to receive the output signal from the first path and the output signal from the second receiver path output and to combine the signals such that the odd-order nonlinear distortion signals are substantially attenuated at an output of the combining element.

Claims

1. A feedforward error-compensated receiver for minimizing undesired odd-order nonlinear distortion products comprising:

a first receiver path having a first path input configured to receive an input signal having at least one non-baseband frequency, and at least one first path output configured to provide a first path output signal having at least one baseband (BB) frequency, said first receiver path comprising at least one mixer, said at least one mixer having a first input terminal electrically coupled to a local oscillator configured to provide a local oscillator signal and having a second input terminal electrically coupled to said first path input and having a mixer output terminal electrically coupled to said at least one first path output, said mixer configured to perform a frequency conversion, said first path output signal comprising an odd-order nonlinear distortion component;

at least one second receiver path having a second path input configured to receive an input signal having at least one non-baseband frequency, and a second receiver path output terminal configured to provide a second receiver path output signal, said second receiver path comprising at least one odd-order nonlinear distortion reference generator having an output terminal, said second receiver path comprising at least one mixer, each of said at least one mixer having a first input terminal electrically coupled to a local oscillator configured to provide a local oscillator signal and having a second input terminal electrically coupled to said at least one odd-order nonlinear distortion reference generator output terminal and having a mixer output terminal electrically coupled to said at least one second path output, said at least one odd-order nonlinear distortion reference generator and said mixer configured to generate a synthetic odd-order nonlinear distortion signal as output that is substantially similar to said odd-order nonlinear distortion component that appears at said first path output terminal; and

a combining element configured to receive said output signal from said first path output terminal and configured to receive said output signal from said second receiver path output terminal and configured to combine said input signals such that the odd-order nonlinear distortion signals are substantially attenuated at an output of said combining element.

2. The feedforward error-compensated receiver of claim 1, wherein said non-baseband frequency is a selected one of a radio frequency (RF) and an intermediate frequency (IF).

3. The feedforward error-compensated receiver of claim 1, wherein said baseband frequency comprises a low intermediate band frequency.

4. The feedforward error-compensated receiver of claim 1, wherein said combining element is configured to use adaptive coupling.

5. The feedforward error-compensated receiver of claim 1, wherein said combining element comprises at least one adaptive equalizer having first and second adaptive equalizer inputs electrically coupled respectively to one of said first path output terminal and a second receiver path output terminal, and having at least one adaptive equalizer output configured to provide an adaptive feedforward error-compensated receiver output signal, said adaptive equalizer including an adaptive filter, said adaptive equalizer configured to automatically adjust a set of adaptive filter coefficients based on a correlation estimate between said adaptive equalizer output and said second receiver path output signal so as to reduce said second receiver path output signal content in said adaptive equalizer output to minimize undesired odd-order distortion products in said adaptive feedforward error-compensated receiver output signal.

6. The feedforward error-compensated receiver of claim 1, wherein said first path comprises a baseband filter configured to attenuate high-frequency signals.

7. The feedforward error-compensated receiver of claim 1, wherein said at least one second receiver path comprises a baseband filter configured to attenuate undesired out of band frequencies.

8. The feedforward error-compensated receiver of claim 1, wherein said undesired out of band frequencies include high-frequency odd-order distortion products.

9. The feedforward error-compensated receiver of claim 1, further comprising a low noise amplifier (LNA) disposed between said input signal and a common signal path coupled to said first path input and said second path input.

10. The feedforward error-compensated receiver of claim 1, wherein said LNA comprises a load inductor having a secondary inductor winding configured as a source-coupled transistor pair.

11. The feedforward error-compensated receiver of claim 1, wherein said feedforward error-compensated receiver comprises a component in a frequency division duplex (FDD) receiver-transmitter.

12. The feedforward error-compensated receiver of claim 1, wherein said feedforward error-compensated receiver comprises a monolithic integrated circuit.

13. The feedforward error-compensated receiver of claim 1, wherein said monolithic integrated circuit comprises a CMOS monolithic integrated circuit.

14. The feedforward error-compensated receiver of claim 1, wherein said odd-order distortion reference generator comprises an analog RF circuit.

15. The feedforward error-compensated receiver of claim 1, wherein said feedforward error-compensated receiver comprises divide-by-two circuits situated adjacent to a LO buffer.

16. The feedforward error-compensated receiver of claim 1, wherein said odd-order nonlinear distortion reference generator is a cubic term generator.

17. The feedforward error-compensated receiver of claim 1, wherein said cubic reference generator comprises a canonical MOS squaring circuit.

18. The feedforward error-compensated receiver of claim 1, wherein a canonical MOS squaring circuit output is electrically coupled to one of two terminals of a source-coupled transistor pair.

19. The feedforward error-compensated receiver of claim 1, wherein said cubic reference generator further comprises a dummy squaring circuit whose output is electrically coupled to another one of said two terminals of said source-coupled transistor pair.

20. The feedforward error-compensated receiver of claim 1, wherein said cubic reference generator comprises a Gilbert cell multiplier configured to perform a final multiplication.

21. The feedforward error-compensated receiver of claim 5, wherein said adaptive equalizer is configured to perform a LMS-based adaptive equalization.

22. The feedforward error-compensated receiver of claim 5, wherein said adaptive equalizer is configured to perform a NLMS-based adaptive equalization.

23. The feedforward error-compensated receiver of claim 5, wherein said adaptive equalizer is configured to perform an enhanced-degree-of-freedom LMS-based or NLMS-based adaptive equalization.

24. The feedforward error-compensated receiver of claim 5, wherein said adaptive equalizer comprises a barrel shifter and said adaptive equalizer is configured to perform a log 2-quantized NLMS algorithm using said barrel shifter.

25. The feedforward error-compensated receiver of claim 1, wherein said second path is configured to be powered “

ON”

following detection of a nonlinear distortion signal corrupting said first receiver path.

26. The feedforward error-compensated receiver of claim 1, wherein said feedforward error-compensated receiver is configured to detect said nonlinear distortion signal corrupting said first receiver path using the analog RF portion of said at least one second receiver path.

27. The feedforward error-compensated receiver of claim 5, wherein said at least one second receiver path along with the adaptive equalizer is configured to be powered fully “

ON”

following detection of a nonlinear distortion signal corrupting the first signal path.

28. The feedforward error-compensated receiver of claim 1, wherein at least one second receiver path and said first path comprises a DC offset correction.

29. The feedforward error-compensated receiver of claim 1, wherein said feedforward error-compensated receiver is configured to measure said DC offset in the absence of IM3 products and wherein said feedforward error-compensated receiver is configured to subtract said DC offset.

30. The feedforward error-compensated receiver of claim 29, wherein said at least one second receiver path is configured to be powered at least in part to correct for said DC offset in the absence of IM3 products.

31. A nonlinear distortion reference generator circuit comprising:

a squaring circuit, said squaring circuit comprising a canonical squaring circuit, said squaring circuit having a squaring circuit output terminal;

a dummy squaring circuit having at least two active device control terminals and a dummy squaring circuit output terminal, said dummy squaring circuit substantially the same as said squaring circuit, said at least two active device control terminals electrically coupled to each other;

a differential source-coupled transistor pair circuit having a first and second differential source-coupled transistor pair input terminals, wherein said squaring circuit output terminal is electrically coupled to said first differential source-coupled transistor pair input terminal and said dummy squaring circuit output terminal is electrically coupled to said second differential source-coupled transistor pair input terminal.

32. The nonlinear distortion reference generator circuit of claim 31, wherein said nonlinear distortion reference generator circuit comprises a CMOS circuit.

33. The nonlinear distortion reference generator circuit of claim 31, wherein said nonlinear distortion reference generator circuit comprises a bipolar transistor-based circuit.

34. A multi-stage nonlinear distortion reference generator circuit comprising:

two or more stages of nonlinear distortion reference generator circuits electrically coupled to each other, wherein said multi-stage nonlinear distortion reference generator circuit is configured to have at least one high-pass filtering transfer function disposed between at least two of said two or more stages of nonlinear distortion reference generator circuits.

35. The multi-stage nonlinear distortion reference generator circuit of claim 34, wherein said at least one high-pass filtering transfer function comprises a frequency-dependent coupling between at least two of said two or more stages of nonlinear distortion reference generator circuits.

36. The multi-stage nonlinear distortion reference generator circuit of claim 34, wherein said at least one high-pass filtering transfer function comprises AC coupling between at least two of said two or more stages of nonlinear distortion reference generator circuits.

37. A detection circuit to detect a presence of undesired odd-order nonlinear distortion comprising:

at least one receiver path having a path input configured to receive an input signal having at least one non-baseband frequency, and a receiver path output terminal configured to provide a receiver path output signal, said receiver path comprising at least one odd-order nonlinear distortion reference generator having an output terminal, said receiver path comprising at least one mixer, each of said at least one mixer having a first input terminal electrically coupled to a local oscillator configured to provide a local oscillator signal and having a second input terminal electrically coupled to said at least one odd-order nonlinear distortion reference generator output terminal and having a mixer output terminal electrically coupled to said at least one path output, said at least one odd-order nonlinear distortion reference generator and said mixer configured to generate a synthetic odd-order nonlinear distortion signal as output, and wherein,

at least one of said at least one receiver paths is electrically coupled to at least one power detector circuit, said at least one power detector circuit configured to measure a magnitude of nonlinear distortion at, at least one of said receiver path output terminals to detect a presence of undesired odd-order nonlinear distortion.

38. The detection circuit of claim 37, wherein said detection circuit comprises a baseband filter configured to attenuate unwanted nonlinear distortion products.

39. The detection circuit of claim 37, wherein said detection circuit comprises a monolithic integrated circuit.

40. The detection circuit of claim 37, wherein said monolithic integrated circuit comprises a CMOS monolithic integrated circuit.

41. The detection circuit of claim 37, wherein said detection circuit comprises a divide-by-two circuit situated adjacent to a LO buffer.

42. The detection circuit of claim 37, wherein said odd-order nonlinear distortion reference generator comprises an analog RF circuit.

43. The detection circuit of claim 37, wherein said odd-order nonlinear distortion reference generator comprises a cubic term generator.

44. The detection circuit of claim 37, wherein said cubic reference generator comprises a canonical MOS squaring circuit.

45. The detection circuit of claim 37, further comprising a source-coupled transistor pair having a first source-coupled transistor pair input and wherein said canonical MOS squaring circuit is electrically coupled to said first source-coupled transistor pair input.

46. The detection circuit of claim 45, wherein said source-coupled transistor pair has a second source-coupled transistor pair input and said cubic reference generator further comprises a dummy squaring circuit electrically coupled to second source-coupled transistor pair input.

47. The detection circuit of claim 37, wherein said cubic reference generator comprises a Gilbert cell multiplier configured to perform a final multiplication.

48. A detection circuit to detect a presence of undesired odd-order nonlinear distortion comprising:

at least one receiver path having a path input configured to receive an input signal having at least one non-baseband frequency, and a receiver path output terminal configured to provide a receiver path output signal, said receiver path comprising at least one odd-order nonlinear distortion reference generator having an output terminal, said receiver path comprising at least one mixer, each of said at least one mixer having a first input terminal electrically coupled to a local oscillator configured to provide a local oscillator signal and having a second input terminal electrically coupled to said at least one odd-order nonlinear distortion reference generator output terminal and having a mixer output terminal electrically coupled to said at least one path output, said at least one odd-order nonlinear distortion reference generator and said mixer configured to generate a synthetic odd-order nonlinear distortion signal as output, and wherein,

at least one of said at least odd-order nonlinear distortion reference generator output terminals is electrically coupled to at least one power detector circuit, said at least one power detector circuit configured to measure a magnitude of nonlinear distortion at said odd-order nonlinear distortion reference generator output terminal to detect a presence of undesired odd-order nonlinear distortion, and wherein,

at least a portion of at least one of said receiver paths is powered-down until a detection of a threshold level of said undesired odd-order nonlinear distortion is exceeded, where-upon detection of exceeding said threshold, said detection circuit causes a powering-ON of all stages of at least one receiver path to perform a cancellation of at least some undesired odd-order nonlinear distortion products.

49. A method to detect the presence of odd-order nonlinear distortion in a radio receiver comprising the steps of:

providing a radio receiver having a first path and at least one second path, at least one of said second paths comprising at least at least one odd-order nonlinear distortion reference generator;

measuring a level of odd-order nonlinear distortion present in said first path based on an output of one of said at least one odd-order nonlinear distortion reference generators; and

comparing said measured level of odd-order nonlinear distortion to a threshold level to detect the presence of odd-order nonlinear distortion in said first path.

50. A method to detect the presence of odd-order nonlinear distortion in a radio receiver comprising the steps of:

providing a radio receiver having a first path and at least one second path, at least one of said second paths comprising at least at least one odd-order nonlinear distortion reference generator;

measuring a level of odd-order nonlinear distortion present in said first path based on an output of one of said second path; and

comparing said measured level of odd-order nonlinear distortion to a threshold level to detect the presence of odd-order nonlinear distortion in said first path.

51. A method to remove a DC offset in a radio receiver comprising the steps of:

providing a radio receiver having at least one signal path having at least one mixer and a local oscillator, said signal path further including at least one averaging circuit to measure a DC offset;

measuring said DC offset using said averaging circuit; and

subtracting a measured DC offset from said signal path to remove said DC offset.

52. The method of claim 51, wherein said steps of measuring said DC offset and subtracting a measured DC offset comprise digital circuits.

53. The method of claim 51, wherein said step of measuring comprises measuring said DC offset using said averaging circuit to generate a measured averaged DC offset value and further high pass filtering said measured averaged DC offset value.

54. The method of claim 51, wherein said step of subtracting comprises subtracting and high pass filtering a measured DC offset from said signal path to remove said DC offset.