RF Power Amplifier Lookup Table Calibration for ET Phase Alignment
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Solution Overview
Problem
In 5G-NR mobile communication devices, the inherent processing delay in envelope tracking (ET) integrated circuits (ETICs) can cause misalignment between the time-variant ET voltage and the time-variant power envelope of RF signals, leading to signal clipping and distortion.
Innovation Solution
A lookup table calibration apparatus and method that includes a power amplifier circuit configured to amplify RF signals based on a modulated voltage and phase-shift the signals using a modulated phase correction voltage. The apparatus concurrently populates and calibrates lookup tables for the modulated voltage and phase correction voltage based on measured gain and phase of the RF signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If envelope tracking is used to improve power amplifier efficiency, then energy consumption is reduced, but processing delay causes misalignment between ET voltage and power envelope leading to signal distortion
Solution Approach 1:
The system performs preliminary calibration by measuring the actual phase and gain of the power amplifier across multiple power levels, then pre-computes correction values and stores them in lookup tables. This preliminary action compensates for the inherent processing delay before actual signal transmission occurs, ensuring accurate alignment without adding real-time processing complexity.
Solution Approach 2:
The calibration process uses feedback by measuring the actual phase and gain of the power amplifier output and using these measurements to update the lookup tables. The system continuously refines the correction values based on measured performance, creating a closed-loop system that improves signal alignment accuracy while maintaining power amplifier efficiency.
2Device complexity
If lookup tables are calibrated separately for voltage and phase, then calibration complexity is reduced, but concurrent calibration provides more accurate alignment
Solution Approach 1:
The system merges the voltage calibration and phase calibration processes into a single concurrent operation. Both lookup tables are populated and calibrated together using the same measurement framework, ensuring that voltage and phase corrections are coordinated and optimized for each power level simultaneously, thereby achieving higher alignment precision.
Solution Approach 2:
The calibration system performs multiple functions simultaneously: it measures both phase and gain, populates both voltage and phase lookup tables, and optimizes both corrections across all power levels in a unified process. This multi-functional approach achieves high measurement precision without proportionally increasing complexity.
Data Source
AI summary
A lookup table calibration apparatus and method are disclosed. The lookup table calibration apparatus includes a power amplifier circuit configured to amplify a radio frequency (RF) signal having time-variant power levels based on a modulated voltage. To ensure proper alignment between the modulated voltage and the time-variant power levels, the power amplifier circuit is further configured to phase-shift the RF signal based on a modulated phase correction voltage. Specifically, the modulated voltage is generated based on a modulated voltage lookup table and the modulated phase correction voltage is generated based on a phase correction voltage lookup table. Herein, the lookup table calibration apparatus can be configured to concurrently populate and/or calibrate the modulated voltage lookup table and the phase correction voltage lookup table based on a measured gain and a measured phase of the RF signal, respectively.