Methods and apparatus for conditioning communications signals based on detection of high-frequency events in polar domain

• US 8,331,490 B2
• Filed: 03/02/2009
• Issued: 12/11/2012
• Est. Priority Date: 10/22/2001
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Wang, Hua, Liang, Paul Cheng-Po, Booth, Richard W. D., Schell, Stephan V., Biedka, Thomas E.
• Primary Examiner(s): Burd, Kevin M.
• Assistant Examiner(s): SHAH, TANMAY K
• Application Number:
  US12/395,981
• Publication Number:
  US 20090257526A1
• Time in Patent Office: 1,380 Days
• Field of Search: 375/308
• US Class Current: 375/308
• CPC Class Codes: H04L 25/03866 using scrambling

Abstract

Methods and apparatus for conditioning communications signals based on detection of high-frequency in the polar domain. High-frequency events detected in a phase-difference component of a complex baseband signal in the polar domain are detected and used as a basis for performing hole-blowing on the complex baseband signal in the quadrature domain and/or nonlinear filtering either or both the magnitude and phase-difference components in the polar domain. Alternatively, high-frequency events detected in the phase-difference signal that correlate in time with low-magnitude events detected in a magnitude component of the complex baseband signal are used as a basis for performing hole-blowing on the complex baseband signal in the quadrature domain and/or nonlinear filtering either or both the magnitude and phase-difference components in the polar domain.

Claims

1. A method of processing a communications signal, comprising:

setting a high-frequency threshold with a frequency detecting unit;

converting in-phase and quadrature components of a baseband signal to magnitude and phase-difference components with a converter unit;

detecting high-frequency events in said phase-difference component during which a rate of change of phase exceeds said high-frequency threshold with the frequency detecting unit;

altering a signal trajectory of said baseband signal, in response to detected high-frequency events;

upconverting said baseband signal after the signal trajectory of said baseband signal has been altered;

coupling an upconverted phase-difference component to a first input of a modulator; and

coupling said magnitude component to a second input of said modulator,

wherein altering the signal trajectory of said baseband signal comprises nonlinear filtering of said magnitude component and nonlinear filtering of said phase-difference component.

2. The method of claim 1 wherein said high-frequency threshold has a frequency based on one of an in-band performance criterion and an out-of-band performance criterion.

3. The method of claim 1 wherein altering the signal trajectory of said baseband signal comprises performing a hole blowing process on said in-phase and quadrature components.

4. The method of claim 1 wherein altering the signal trajectory of said baseband signal comprises nonlinear filtering of said phase-difference component.

5. The method of claim 4 wherein nonlinear filtering said phase-difference component comprises reducing a rate of change of phase of said baseband signal along the signal trajectory of said baseband signal.

6. The method of claim 1 wherein altering the signal trajectory of said baseband signal comprises adjusting the magnitude of said baseband signal along the signal trajectory of said baseband signal.

7. The method of claim 1 wherein said high-frequency threshold has a frequency based on a balance or combination of in-band and out-of-band performance criteria.

8. The method of claim 1, further comprising:

setting a low-magnitude threshold;

detecting low-magnitude events in said magnitude component during which the magnitude of said magnitude component falls below said low-magnitude threshold; and

altering the signal trajectory of said baseband signal, in response to detected low-magnitude events that correlate in time with respect to detected high-frequency events.

9. An apparatus for conditioning a communications signal, comprising:

a rectangular-to-polar converter configured to convert in-phase and quadrature components of a baseband signal to magnitude and phase components;

a phase-difference calculator configured to convert said phase component to a phase-difference component;

frequency detecting means configured to detect high-frequency events in said phase-difference component having a rate of change of phase exceeding a high-frequency threshold;

means for altering a signal trajectory of said baseband signal, in response to detected high-frequency events; and

a modulator having a first input configured to receive said magnitude component and a second input configured to receive an upconverted phase-difference component, after said means for altering the signal trajectory has altered the signal trajectory of said baseband signal.

10. The apparatus of claim 9 wherein said high-frequency threshold has a frequency based on either an in-band performance criterion or an out-of-band performance criterion.

11. The apparatus of claim 10 wherein said means for altering the signal trajectory of said baseband signal comprises means for altering magnitudes of said in-phase and quadrature components.

12. The apparatus of claim 9 wherein said means for altering the signal trajectory of said baseband signal comprises a nonlinear filter configured to alter a rate of change of phase of said phase-difference component.

13. The apparatus of claim 9 wherein said means for altering the signal trajectory of said baseband signal comprises a nonlinear filter configured to alter the magnitude of said magnitude component.

14. The apparatus of claim 13 wherein said means for altering the signal trajectory of said baseband signal further comprises a nonlinear filter configured to alter the frequency of said phase-difference component.

15. The apparatus of claim 9, further comprising magnitude detecting means configured to detect low-magnitude events in said magnitude component having magnitudes falling below a low-magnitude threshold.

16. The apparatus of claim 15 wherein said means for altering the signal trajectory of said baseband signal is configured to alter the signal trajectory of said baseband signal, in response to detected low-magnitude events in said magnitude component that correlate in time with detected high-frequency events in said phase-difference component.

17. The apparatus of claim 9 wherein said high-frequency threshold has a frequency based on a balance or combination of in-band and out-of-band performance criteria, instead of on said in-band performance criterion or said out-of-band performance criterion.