Broadband Power Amplifier Bias Control for Linearity and Efficiency
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Solution Overview
Problem
Broadband power amplifiers in mobile communication devices face challenges in achieving a balance between linearity and efficiency, particularly due to high peak-to-average ratio (PAR) signals in 5G systems, which lead to undesirable spectral regrowth and distortion, and the memory effect in class-AB operation modes.
Innovation Solution
A broadband power amplifier circuit that opportunistically adjusts bias voltage and supply voltage based on predicted output power in future time slots, allowing for class-A operation while maintaining linearity and avoiding memory effects, thereby improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the broadband PA operates in class-A mode with sufficient back-off to improve linearity performance, then linearity is improved, but PA efficiency is reduced
Solution Approach 1:
The patent applies dynamics by transitioning from a static class-A operation mode to a dynamic mode where the PA switches between class-A and class-AB modes based on instantaneous signal conditions. The control circuit dynamically adjusts the operation mode according to the envelope signal characteristics, allowing the system to optimize between linearity and efficiency in real-time rather than being constrained to a fixed mode.
Solution Approach 2:
The patent changes the operational parameters of the PA by introducing variable back-off control. Instead of maintaining a fixed back-off level required for class-A operation, the system dynamically adjusts the back-off amount based on the envelope signal prediction, enabling the PA to operate at optimal efficiency points while maintaining acceptable linearity through predictive compensation.
2Use of energy by moving object
If the broadband PA operates in class-AB mode to improve PA efficiency, then efficiency is improved, but linearity performance is compromised and memory effect occurs
Solution Approach 1:
The patent applies preliminary action through envelope signal prediction and advance control signal generation. The control circuit predicts future envelope signal values and generates corresponding control signals in advance, allowing the PA to be pre-positioned in the appropriate operation mode before high-power signals occur, thereby preventing memory effect and maintaining linearity while enabling efficiency improvements.
Solution Approach 2:
The patent implements feedback mechanisms where the control circuit continuously monitors the PA output and adjusts the operation mode accordingly. The envelope detection and prediction circuits provide feedback about signal characteristics, enabling the system to respond to changing conditions and maintain optimal performance by switching between class-A and class-AB modes based on real-time signal analysis.
3Power
If the broadband PA increases output power to achieve higher data rates and coverage range, then data rate and coverage are improved, but spectral regrowth and distortion increase
Solution Approach 1:
The patent applies dynamics by enabling the PA to adapt its operation mode dynamically based on instantaneous power requirements. Rather than operating continuously in a fixed mode that compromises linearity at high power, the system transitions between class-A (for linearity at high power) and class-AB (for efficiency at lower power), thereby maintaining signal quality across the full output power range while achieving higher data rates and coverage.
Data Source
AI summary
A broadband power amplifier circuit is provided. The broadband power amplifier circuit includes an amplifier circuit configured to amplify a radio frequency (RF) signal to an output power based on a bias voltage and a supply voltage. Given that the output power of the RF signal may rise and fall from time to time, the broadband power amplifier circuit is configured to opportunistically increase or decrease the bias voltage in a defined future time (e.g., a future time slot or a future symbol duration) based on the output power in the defined future time. When necessary, the broadband power amplifier may be further configured to adjust the supply voltage and/or attenuate the RF signal based on the output power. As such, it may be possible to maintain class-A operation mode for the amplifier circuit. As a result, the amplifier circuit may maintain linearity and avoid memory effect with improved efficiency.