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 crest factor reduction block and digital predistortion system to optimize energy use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If power amplifiers operate at high drain voltages to maintain signal integrity during peak power transmission, then signal quality is preserved, but energy consumption increases significantly
Solution Approach 1:
The patent implements dynamic drain voltage adjustment by tracking the RF signal envelope with a bias voltage that changes over time. The voltage modulator dynamically adjusts the drain voltage of the power amplifier transistor based on the instantaneous signal power level, allowing the amplifier to operate at lower voltages during low-power periods and maintain high voltage only when necessary for signal integrity during peak transmission.
Solution Approach 2:
The patent changes the operating parameters of the power amplifier by varying the drain voltage level according to the signal envelope. The bias voltage is modulated to match the RF signal power variations, transforming the amplifier from a static high-voltage operation to a dynamic variable-voltage operation, thereby reducing energy consumption while maintaining signal quality when needed.
2Use of energy by moving object
If power amplifiers operate at lower drain voltages to reduce energy consumption, then energy efficiency improves, but signal integrity may be compromised
Solution Approach 1:
The system dynamically adjusts the drain voltage to the minimum necessary level for each instant of signal transmission. By tracking the RF envelope, the bias voltage is optimized in real-time, allowing lower voltage operation during low-power symbols while automatically increasing voltage during high-power transmission to maintain signal integrity, thus resolving the trade-off between energy efficiency and reliability.
Solution Approach 2:
The patent employs feedback mechanisms where the RF signal envelope is detected and used to control the bias voltage generation. The voltage modulator receives feedback from the signal power level and adjusts the drain voltage accordingly, ensuring that the amplifier operates at the optimal voltage level that maintains signal integrity while minimizing energy consumption.
3Reliability
If continuous high power transmission is maintained to ensure coverage, then service reliability is improved, but energy consumption increases
Solution Approach 1:
The patent utilizes the periodic nature of digital communication signals, where data is transmitted in discrete symbols with varying power levels. By detecting the envelope of these periodic signals and adjusting the bias voltage accordingly, the system maintains high power transmission only when data symbols require it, while reducing power during lower transmission requirements, thus improving energy efficiency without compromising overall service reliability.
Solution Approach 2:
The system transitions from static continuous high-power operation to dynamic power adjustment that follows the signal envelope. The bias voltage modulator dynamically tracks the RF signal variations, enabling the power amplifier to adapt its output power level to match the actual transmission needs, maintaining service reliability when high power is required while reducing energy consumption during lower power transmission periods.
Data Source
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 digital predistortion system in a signal path that provides the radio frequency signal can adjust a digital predistortion based on a symbol based envelope tracking state.