Envelope Tracking LUT Calibration Using PA Output Feedback
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Solution Overview
Problem
Existing envelope tracking (ET) lookup tables in mobile communication devices lack accuracy, leading to inefficiencies and increased power consumption and thermal dissipation in power amplifiers, which compromises performance and user experience.
Innovation Solution
A calibration circuit within the power management integrated circuit (PMIC) determines a linear relationship between input and output power to calibrate the ET lookup table without requiring coupling to an antenna, improving the accuracy and linearity of power amplifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If envelope tracking is implemented to improve power amplifier efficiency, then operating efficiency improves, but lookup table accuracy deteriorates leading to increased power consumption
Solution Approach 1:
The patent applies preliminary action by performing lookup table calibration before actual operation. The calibration circuit pre-determines the linear relationship between input and output power to correct lookup table inaccuracies beforehand, ensuring accurate envelope tracking during normal operation without requiring real-time adjustments that would consume additional power.
Solution Approach 2:
The patent implements feedback by using output power feedback from the power amplifier to the calibration circuit. The calibration circuit continuously monitors the actual output power and adjusts the lookup table values based on the difference between expected and actual output, thereby improving lookup table accuracy while maintaining power amplifier efficiency.
2Manufacturing precision
If lookup table accuracy is improved through calibration, then power amplifier linearity improves, but device complexity increases due to additional calibration circuitry
Solution Approach 1:
The patent merges the calibration circuit with the existing power management integrated circuit (PMIC) that controls the power amplifier. By integrating the calibration functionality into the existing PMIC structure rather than adding a separate standalone calibration device, the patent improves power amplifier linearity while minimizing the increase in overall device complexity.
Solution Approach 2:
The calibration circuit is designed to perform multiple functions: it calibrates the lookup table for accurate envelope tracking, monitors output power levels, and adjusts power amplifier operation. This multi-functionality reduces the need for separate dedicated circuits, thereby improving linearity without proportionally increasing device complexity.
3Measurement precision
If antenna coupling is required for calibration, then measurement accuracy improves, but ease of operation deteriorates due to additional connection requirements
Solution Approach 1:
The patent extracts the calibration measurement function from the antenna interface and implements it using the existing output power feedback path within the power amplifier system. By taking out the calibration requirement from the antenna coupling domain and implementing it through internal feedback signals, the patent achieves accurate calibration measurements without requiring additional antenna connections or external measurement equipment.
Data Source
AI summary
An apparatus and method for calibrating an envelope tracking (ET) lookup table (LUT) are provided. An ET power management apparatus includes a power amplifier configured to amplify a radio frequency (RF) signal from a time-variant input power to a time-variant output power linearly related to the time-variant input power. A calibration circuit is employed to receive a time-variant output power feedback nonlinearly related to the time-variant input power, determine a linear relationship between the time-variant input power and the time-variant output power based on the time-variant output power feedback, and calibrate the ET LUT based on the determined linear relationship. As a result, it is possible to improve accuracy of the ET LUT to thereby improve operating efficiency and linearity of the power amplifier.