Symbol-Based Envelope Tracking for RF Power Amplifier Efficiency

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Solution Overview

Problem

Power amplifiers in radio systems consume significant energy, and existing technologies have struggled to efficiently reduce energy consumption while maintaining performance, especially in wireless base stations with varying RF power output levels.

Innovation Solution

A power amplifier system with symbol-based envelope tracking that generates an output bias voltage tracking the root mean square symbol power of a radio frequency signal, adjusting the voltage on symbol boundaries and incorporating a digital predistortion system to optimize crest factor reduction and energy efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If power amplifiers operate at high drain voltages to maintain signal integrity, then signal quality is preserved, but energy consumption increases significantly

Engineering Contradiction:

Improvesignal integrityVSAvoidenergy consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent implements dynamic drain voltage adjustment by tracking the envelope of the RF signal. The drain voltage is modulated to follow the signal envelope, allowing the power amplifier to operate at lower voltages during low-power portions of the signal while maintaining adequate voltage during high-power portions, thus preserving signal integrity only when necessary

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the drain voltage parameter dynamically based on the signal envelope. By adjusting the drain voltage to match the instantaneous power requirements of the RF signal, the system reduces energy consumption during low-power intervals while maintaining signal quality during high-power intervals

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If power amplifiers operate at reduced drain voltages to save energy, then energy consumption decreases, but signal integrity may be compromised

Engineering Contradiction:

Improveenergy consumptionVSAvoidsignal integrity

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent employs feedback mechanisms where the drain voltage is continuously adjusted based on the detected signal envelope. This closed-loop control ensures that the drain voltage remains sufficient to maintain signal integrity while minimizing energy consumption by reducing voltage during low-power signal portions

Inventive Principle:

Principle #23Feedback

3Power

If continuous high voltage is applied to power amplifier, then maximum power output is maintained, but energy waste increases during low power transmission

Engineering Contradiction:

Improvepower outputVSAvoidenergy waste

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

The patent applies periodic modulation to the drain voltage that follows the periodic nature of the RF signal envelope. By synchronizing the voltage modulation with the signal periodicity, the system maintains maximum power output capability when needed while reducing voltage and minimizing energy waste during low-power transmission intervals

Inventive Principle:

Principle #19Periodic action

Data Source

PatentUS20250015769A1Symbol based envelope tracking and crest factor reduction

Publication Date: 2025.01.09 ANALOG DEVICES INT UNLTD CO

AI summary

Aspects of this disclosure relate to symbol based envelope tracking. A voltage modulator circuit can generate an output bias voltage that tracks a root mean square symbol power of a radio frequency signal. A crest factor reduction circuit in a signal path that provides the radio frequency signal can adjust a crest factor reduction threshold such that the crest factor reduction threshold corresponds to the output bias voltage.