Envelope Tracking Shaping for Low-Noise Power Amplifiers
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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 a first ET shaping function and a modulator to establish a relationship between a baseband signal and a voltage as Vpa=a|X|2+b, using a look-up table to calculate constants a and b, and incorporating a Digital Pre-Distortion (DPD) function to compensate for PA non-linearity, thereby reducing power supply noise and avoiding saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If envelope tracking (ET) is used to improve TX 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 to reduce power supply noise while maintaining TX efficiency improvements
Solution Approach 2:
The patent uses Digital Pre-Distortion (DPD) function to pre-compensate for PA non-linearity before the signal is amplified. This preliminary action prevents distortion and noise issues from occurring during the amplification process
2Productivity
If conventional ET shaping function is used, then TX efficiency is improved, but PA saturation occurs and DPD cannot effectively compensate for non-linearity
Solution Approach 1:
The patent changes the voltage-power relationship parameter from linear to quadratic by using Vpa = a|X|^2 + b instead of the conventional linear relationship. This parameter change ensures the PA operates within its linear region, preventing saturation and enabling effective DPD compensation
Solution Approach 2:
The patent incorporates a look-up table that records the relation curve between power and voltage, which provides feedback information to calculate optimal constants a and b. This feedback mechanism ensures the PA operates reliably without saturation
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.