Envelope-Tracking Supply Timing Alignment for RF Amplifiers
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Solution Overview
Problem
Existing RF power amplifiers face timing misalignment issues due to delays in the pre-processing and path delays, leading to inefficiencies and unwanted sidebands, which are difficult to compensate for without complex demodulation techniques unsuitable for mobile equipment.
Innovation Solution
A method to measure and adjust the timing misalignment between the RF signal and the envelope-tracking modulated power supply by comparing the relative timing of current and voltage signals, allowing for compensation without demodulating RF signals, using a comparator and delay stage to align the signals effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If envelope tracking is implemented to improve amplifier efficiency, then energy efficiency is improved, but timing misalignment occurs between the RF signal and modulated power supply due to delays in pre-processing and path delays
Solution Approach 1:
The patent applies preliminary action by measuring the timing misalignment between the RF signal path and the modulated power supply path, then compensating for this misalignment by adjusting the timing of the modulated power supply voltage. This is achieved by comparing the relative timing of current drawn by the amplifier from the modulated supply with the voltage generated at the output of the modulated supply, and adjusting the timing of either the input signal or generated supply voltage to reduce the timing difference, thereby ensuring proper synchronization before the amplification process occurs.
2Measurement precision
If complex demodulation techniques are used to compensate for timing misalignment, then timing accuracy is improved, but device complexity increases making it unsuitable for mobile equipment
Solution Approach 1:
The patent extracts the essential timing information needed for alignment by comparing only the relative timing of the current and voltage signals from the modulated power supply, rather than performing full complex demodulation of the RF signal. This extraction approach obtains sufficient timing data with minimal processing complexity, avoiding the need for full signal demodulation while still achieving accurate timing compensation suitable for mobile devices.
Solution Approach 2:
The system uses signals already present in the amplifier operation (the current drawn from the modulated supply and the voltage generated at the output) to perform the timing alignment measurement. This self-service approach eliminates the need for external test signals or complex demodulation circuits, as the amplifier's own operating signals provide the necessary timing information for compensation.
3Device complexity
If timing misalignment is not compensated, then device complexity remains low, but unwanted sidebands are generated and efficiency is reduced
Solution Approach 1:
The patent implements feedback by continuously monitoring the relative timing between the current drawn by the amplifier and the voltage generated at the output of the modulated supply, then using this timing information to adjust the timing of the modulated power supply voltage. This closed-loop feedback mechanism automatically compensates for timing misalignment, preventing the generation of unwanted sidebands and maintaining efficiency without requiring complex open-loop compensation circuits.
Data Source
AI summary
There is disclosed a method, in an amplifier stage comprising an amplifier and a modulated supply, the amplifier being arranged to amplify an input signal and the modulated supply being arranged to generate a supply voltage for the amplifier by tracking an envelope of the signal to be amplified, the method comprising: comparing the relative timing of a signal representing the current drawn by the amplifier from the modulated supply and a signal representing the voltage generated at the output of the modulated supply; and in dependence upon a difference in the relative timing, adjusting the timing of either the input signal to be amplified or the generated supply voltage to reduce the difference in the relative timing.