Symbol-Based Envelope Tracking With Crest Factor Threshold Control
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Solution Overview
Problem
Current radio frequency power amplifiers in wireless base stations consume significant energy, especially since they often operate at maximum capacity only for a small fraction of the time, making it challenging to achieve energy savings without increasing initial equipment costs.
Innovation Solution
The implementation of a power amplifier system with symbol-based envelope tracking, which generates an output bias voltage that tracks the root mean square symbol power of a radio frequency signal on a symbol-by-symbol basis, allowing for efficient adjustment of crest factor reduction thresholds and digital predistortion, thereby reducing energy consumption by operating at lower drain voltages during lower power symbols.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If power amplifiers operate at maximum capacity to maintain signal quality, then signal integrity is improved, but energy consumption increases
Solution Approach 1:
The patent implements dynamic drain voltage adjustment that tracks the envelope of the RF signal, allowing the power amplifier to operate at optimal voltage levels for each signal condition. The drain voltage is modulated according to the signal envelope, enabling the amplifier to use lower voltage during low-power symbols and maximum voltage during high-power symbols, thus resolving the contradiction between maintaining signal integrity and reducing energy consumption.
Solution Approach 2:
The patent changes the operating parameters of the power amplifier by dynamically adjusting the drain voltage level based on the signal envelope. This parameter change allows the amplifier to adapt its operating point, using lower voltage for low-power signals and higher voltage for high-power signals, thereby reducing overall energy consumption while maintaining signal quality when needed.
2Use of energy by moving object
If power amplifiers operate at lower voltages to save energy, then energy consumption is reduced, but signal quality deteriorates
Solution Approach 1:
The dynamic envelope tracking ensures that the drain voltage is adjusted in real-time to match the signal envelope, providing maximum voltage only when the signal requires it and lower voltage during low-power periods. This dynamic adaptation maintains signal quality during critical moments while reducing energy consumption during non-critical periods.
Solution Approach 2:
By changing the drain voltage parameter dynamically based on the signal envelope, the system optimizes the trade-off between energy consumption and signal quality. The voltage parameter is adjusted to provide high quality when needed and conserve energy when signal requirements are lower.
3Use of energy by moving object
If voltage transitions occur frequently to track signal envelope, then energy efficiency is improved, but device complexity increases
Solution Approach 1:
The patent segments the voltage control into discrete levels that correspond to different signal power ranges. Instead of continuous voltage adjustment, the system uses segmented voltage levels that are switched based on the signal envelope, reducing the complexity of the voltage modulation circuitry while maintaining energy efficiency benefits.
Solution Approach 2:
The system implements dynamic voltage switching with controlled transition frequencies. By managing the frequency and timing of voltage transitions, the system achieves energy efficiency improvements while preventing excessive switching that would increase device complexity and power loss.
Data Source
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Figure 3A~3C
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.