Power Amplifier Time-Delay Invariant Predistortion Methods and Apparatus

• US 20080174365A1
• Filed: 01/28/2008
• Published: 07/24/2008
• Est. Priority Date: 05/01/2002
• Status: Active Grant

• Current Assignee: Dali Wireless Inc. (Dali Systems Co., Ltd.)
• Original Assignee: Dali Systems Co., Ltd.
• Inventors: Yang, Dali, Yang, Jia
• Granted Patent: US 8,380,143 B2
• Time in Patent Office: Days
• US Class Current: 330/149
• CPC Class Codes: H03F 1/3241 using predistortion circuits H03F1/3211, H03F1/3217 take precedence
• CPC Class Codes: H03F 1/3247 using feedback acting on predistortion circuits H03F1/3264 takes precedence
• CPC Class Codes: H03F 2200/451 the amplifier being a radio frequency amplifier
• CPC Class Codes: H03F 2200/57 Separate feedback of real and complex signals being present
• CPC Class Codes: H03F 2201/3224 Predistortion being done for compensating memory effects
• CPC Class Codes: H03F 2201/3233 Adaptive predistortion using lookup table, e.g. memory, RAM, ROM, LUT, to generate the predistortion
• CPC Class Codes: H03F 3/24 of transmitter output stages
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04B 2001/0425 with linearisation using predistortion
• CPC Class Codes: H04L 1/0044 specially adapted for power saving

Abstract

An embodiment of the invention is a time-delay invariant predistortion approach to linearize power amplifiers in wireless RF transmitters. The predistortion architecture is based on the stored-compensation or memory-compensation principle by using a combined time-delay addressing method, and therefore, the architecture has an intrinsic, self-calibrating time-delay compensation function. The predistortion architecture only uses a lookup table to conduct both the correction of non-linear responses of a power amplifier and the compensation of any time-delay effects presented in the same system. Due to the time-delay invariant characteristic, the predistortion design has a wider dynamic range processing advantage for wireless RF signals, and therefore can be implemented in multi-carrier and multi-channel wireless systems.

Claims

1. A predistortion system for linearizing the output of a power amplifier comprising

a first signal representative of an RF modulated signal,

a feedback signal representative of nonlinear characteristics of a power amplifier,

a predistortion controller, comprising at least one lookup table of a predetermined size, adapted to receive the first signal and the feedback signal and to generate a correction factor for correcting the nonlinear characteristics of the power amplifier and wherein the values of the lookup table fall within a range determined by the size of the table, and

combining logic which combines the RF modulated signal with a signal corresponding to the correction factor and supplies it to the power amplifier to linearize the output of the power amplifier.

2. The predistortion system of claim 1 further comprising a serial shift register for forming an address for the lookup table.

3. The predistortion system of claim 1 wherein the lookup table is addressed by parallel signals.

4. The predistortion system of claim 1 wherein the values of the lookup table automatically compensate for time delay of the signals through different transmission paths.

5. A predistortion system for linearizing the output of a power amplifier comprising

a first signal representative of an RF modulated signal,

a feedback signal representative of nonlinear characteristics of a power amplifier,

a predistortion controller comprising an address former and a lookup table wherein the values in the lookup table are time invariant and are based on the operating characteristics of the power amplifier and related system, and

combining logic which combines the RF modulated signal with a signal corresponding to a time-invariant correction factor supplied by the lookup table.

6. A method for linearizing the output of a power amplifier comprising

providing an RF modulated signal representative of an ideal signal,

providing a feedback signal representative of nonlinear characteristics of a power amplifier,

sampling a plurality of samples representative of a range of error characteristics of the power amplifier and associated transmission system, including time delays,

determining a plurality of time-invariant error correction factors in response to the samples,

providing an error correction signal representative of one of the correction factors for linearizing the output of the power amplifier.