Envelope Tracking Shaping for PA Noise and Linearity
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Solution Overview
Problem
Envelope tracking (ET) introduces worse power supply noise compared to average power tracking (APT), leading to increased TX noise, and existing designs fail to optimize ET without degrading power amplifier (PA) noise.
Innovation Solution
An electronic device with a processor executing an ET shaping function Vpa=a|X|2+b, using a look-up table to calculate constants a and b, and a modulator to output a voltage based on the baseband signal magnitude, combined with a power amplifier and RF circuit to reduce power supply noise and compensate for PA non-linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If envelope tracking (ET) is used to improve transmitting efficiency, then TX efficiency is improved, but power supply noise increases leading to worse TX noise
Solution Approach 1:
The patent applies parameter changes by modifying the ET shaping function from the conventional linear relationship to a quadratic relationship (Vpa = a*|X|^2 + b). This changes the voltage-power relationship parameters, allowing the system to maintain efficient TX performance while reducing power supply noise. The look-up table stores pre-calculated voltage values based on this quadratic relationship, enabling the processor to select optimal voltage levels that reduce noise while maintaining efficiency.
2Productivity
If conventional ET shaping function is used, then TX efficiency is improved, but power amplifier saturation occurs and non-linearity increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing the optimal voltage values in a look-up table before actual transmission. The table contains pre-determined voltage values corresponding to different signal magnitudes, allowing the processor to quickly select appropriate voltage levels without real-time complex calculations. This preliminary preparation ensures that the power amplifier operates within its linear region while maintaining efficiency, avoiding saturation and non-linearity issues.
Solution Approach 2:
The patent implements feedback through the look-up table mechanism, where the processor selects voltage values based on the actual signal magnitude and the pre-stored relationship. This feedback approach allows the system to adapt to varying signal conditions while maintaining optimal operating points that prevent power amplifier saturation and non-linearity, thereby preserving both efficiency and reliability.
Data Source
AI summary
An electronic device includes a processor, a modulator, and a power amplifier. The processor receives a baseband signal and executes a first ET shaping function on the baseband signal. The modulator receives the baseband signal, detects the magnitude of the baseband signal, and outputs the first voltage according to the magnitude of the baseband signal. The power amplifier outputs an amplified signal based on the first voltage. The first ET shaping function enables the relationship between the baseband signal and the first voltage to be Vpa=a|X|2+b. X is the baseband signal, Vpa is the first voltage, and a and b are constants. The look-up table records the relation curve between the power of the amplified signal and the first voltage when the second ET shaping function is used for envelope tracking.