Multiple stage and/or nested predistortion system and method

• US 20030031270A1
• Filed: 08/13/2001
• Published: 02/13/2003
• Est. Priority Date: 08/13/2001
• Status: Active Grant

• Current Assignee: WSOU Investments, LLC (WSOU Holdings, LLC)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Lai, Haobo, Kim, Jaehyeong, Giardina, Charles Robert
• Granted Patent: US 6,931,080 B2
• Time in Patent Office: Days
• US Class Current: 375/296
• CPC Class Codes: H03F 1/3247 using feedback acting on predistortion circuits H03F1/3264 takes precedence

Abstract

A multiple stage and/or nested predistortion system and method uses an inner predistortion function to adjust a signal being input into a distortion generating circuit and at least one outer predistortion function to adjust the signal being input into the inner predistortion function. Thus, the inner predistortion function can reduce the distortion from the distortion generating circuitry, and any remaining distortion can be reduced by the outer predistortion function. For example, in an adaptive predistortion system where the distortion generating circuit is an amplifier, an inner predistortion loop comprises an inner predistortion function which distorts the signal on the main signal path prior to the amplifier. The inner predistortion function can be produced using an output of the inner predistortion function and an output of the amplifier. An outer predistortion loop comprises an outer predistortion function which distorts the input signal prior to the inner predistortion function. The outer predistortion function can be determined using an output to the outer predistortion function and the output to the inner predistortion loop. As such, the signal on the signal path is predistorted in multiple stages prior to the amplifier to compensate for the distortion generated by the amplification of the signal, and the resulting amplified signal is produced with reduced distortion.

Claims

1. A method of predistorting an input signal, said method comprising:

using at least one outer predistortion function to adjust a signal to produce a predistorted signal to an inner predistortion function; and

adjusting said predistorted signal using said inner predistortion function prior to a distortion generating circuit.

2. The method of claim 1 comprising:

producing said inner predistortion function using an output of said inner predistortion function and an output of said distortion generating circuitry.

3. The method of claim 1 comprising:

producing said outer predistortion function using an output of said outer predistortion function and an output of said distortion generating circuitry.

4. The method of claim 1 comprising:

using an amplifier as said distortion generating circuitry.

8. The system of claim 1 wherein said distortion generating circuit is an amplifier.

5. A predistortion system comprising:

a distortion generating circuit; and

predistortion circuitry adapted to use at least one outer predistortion function to adjust a signal to produce a predistorted signal to an inner predistortion function, and to adjust said predistorted signal using said inner predistortion function prior to said distortion generating circuit.

6. The system of claim 5 wherein said predistortion circuitry is configured to produce said inner predistortion function using an output of said inner predistortion function and an output of said distortion generating circuitry.

7. The system of claim 5 wherein said predistortion circuitry is configured to produce said outer predistortion function using an output of said outer predistortion function and an output of said distortion generating circuitry.