# US 2008/0174365 A1 · Power Amplifier Time-Delay Invariant Predistortion Methods and Apparatus

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 2008/0174365 A1
- Document ID: US20080174365A1
- Status: Published application
- Kind: A1
- Application number: 12/021,241
- Filed: 2008-01-28
- Published: 2008-07-24
- Earliest claimed: 2002-05-01
- Assignees: Dali Systems Co. Ltd.
- Inventors: Dali Yang; Jia Yang
- Web page: https://patentgrep.com/patent/US20080174365A1

## CPC

- H03F 1/3247: {using feedback acting on predistortion circuits (H03F1/3264 takes precedence)}
- H03F 1/3241: {using predistortion circuits (H03F1/3211, H03F1/3217 take precedence)}
- H03F 3/24: of transmitter output stages
- H04B 1/0475: {with means for limiting noise, interference or distortion (H04B1/0483 takes precedence)}
- H04L 1/0044: {specially adapted for power saving}
- H03F 2200/451: the amplifier being a radio frequency amplifier
- H03F 2200/57: Separate feedback of real and complex signals being present
- H03F 2201/3224: Predistortion being done for compensating memory effects
- H03F 2201/3233: Adaptive predistortion using lookup table, e.g. memory, RAM, ROM, LUT, to generate the predistortion
- H04B 2001/0425: {with linearisation using predistortion}
- H03F: AMPLIFIERS
- H04B: TRANSMISSION
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## 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

### Claim 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.

### Claim 2 (depends on 1)

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

### Claim 3 (depends on 1)

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

### Claim 4 (depends on 1)

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.

### Claim 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.

### Claim 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.