METHOD AND APPARATUS FOR PROVIDING A CARTESIAN TRAINING WAVEFORM

• US 20080299922A1
• Filed: 05/31/2007
• Published: 12/04/2008
• Est. Priority Date: 05/31/2007
• Status: Active Grant

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: VAN CANNON, BILLY J., LIETZ, THEODORE M., CHAIDEZ, APOLINAR
• Granted Patent: US 7,719,355 B2
• Time in Patent Office: Days
• US Class Current: 455/126
• CPC Class Codes: H03F 1/3247 using feedback acting on predistortion circuits H03F1/3264 takes precedence
• CPC Class Codes: H03F 1/3294 Acting on the real and imaginary components of the input signal

Abstract

One provides (401, 402) both an in-phase signal component (501) and a quadrature signal component (601) wherein the latter has a non-zero portion. These two signal components are then combined (403) to provide a Cartesian training waveform that can be used when training a linear amplifier that uses Cartesian feedback linearization. By one approach, the non-zero portion of the quadrature signal component can be coincident with a zero-crossing portion of the in-phase signal. In many application settings this non-zero portion of the quadrature signal component can be less (and sometimes considerably less) than a peak amplitude of the in-phase signal component. One may also shape the in-phase signal component to have a smoothed envelope. This may include, for example, using a smoothed sine wave such as a raised-sine function.

Claims

1. A method of providing a Cartesian training waveform for use when training a linear amplifier that uses Cartesian feedback linearization, comprising:

providing an in-phase signal component;

providing a quadrature signal component having a non-zero portion;

combining the in-phase signal component and the quadrature signal component to provide the Cartesian training waveform.

2. The method of claim 1 wherein the in-phase signal component comprises a zero-crossing portion.

3. The method of claim 2 wherein the non-zero portion of the quadrature signal component is coincident with the zero-crossing portion of the in-phase signal.

4. The method of claim 1 wherein the non-zero portion of the quadrature signal component has an amplitude that is less than a peak amplitude of the in-phase signal component.

5. The method of claim 4 wherein the non-zero portion of the quadrature signal component amplitude is minimized.

6. The method of claim 1 wherein the quadrature signal component also has at least one zero amplitude portion, wherein the at least one zero amplitude portion coincides temporally with a maximum amplitude of the in-phase signal.

7. The method of claim 1 wherein the in-phase component comprises, at least in substantial part, a sine wave.

8. The method of claim 7 wherein the sine wave comprises a smoothed sine wave.

9. The method of claim 8 wherein the smoothed sine wave comprises a raised-sine function.

10. An apparatus comprising:

a linear amplifier that uses Cartesian feedback linearization and that comprises, in part, a Cartesian training waveform input;

a training waveform source having an output operably coupled to the Cartesian training waveform input and being configured and arranged to;

provide an in-phase signal component;

provide a quadrature signal component having a non-zero portion;

combine the in-phase signal component and the quadrature signal component to provide a Cartesian training waveform to the output.

11. The apparatus of claim 10 wherein the in-phase signal component comprises a zero-crossing portion.

12. The apparatus of claim 11 wherein the non-zero portion of the quadrature signal component is coincident with the zero-crossing portion of the in-phase signal.

13. The apparatus of claim 10 wherein the non-zero portion of the quadrature signal component has an amplitude that is less than a peak amplitude of the in-phase signal component.

14. The apparatus of claim 10 wherein the non-zero portion of the quadrature signal component amplitude is minimized.

15. The apparatus of claim 10 wherein the in-phase signal component lacks any abrupt power changes over time.

19. The apparatus of claim 10 wherein the training waveform source comprises:

means for providing an in-phase signal component;

means for providing a quadrature signal component having a non-zero portion;

means for combining the in-phase signal component and the quadrature signal component to provide the Cartesian training waveform.

16. The apparatus of 10 wherein the in-phase component comprises, at least in substantial part, a sine wave.

17. The apparatus of claim 16 wherein the sine wave comprises a smoothed sine wave.

18. The apparatus of claim 17 wherein the smoothed sine wave comprises a raised-sine function.