Envelope Tracking Amplifier Feedback for Delay and Offset Tuning
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Solution Overview
Problem
The Envelope Tracking concept for power amplification in base stations is hindered by the need for accurate delay and offset compensation between RF signals and modulated supply voltages to prevent signal distortions and maintain efficiency, which is challenging due to phase misalignment.
Innovation Solution
An envelope tracking arrangement that uses a digital signal processing unit to compare error measures such as error vector magnitude and modulation error ratio between RF input and output signals, allowing for independent adjustment of delay and offset, and incorporates a feedback path for linearization and pre-distortion of the baseband signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If Envelope Tracking concept is used to improve power amplifier efficiency, then energy efficiency is improved, but phase alignment accuracy deteriorates due to difficulty in delay compensation between RF signal and modulated supply voltage
Solution Approach 1:
The patent implements a feedback mechanism where the RF signal is tapped at both input and output of the power transistor, converted to digital domain, and processed by a signal processing unit that calculates error measures (EVM, modulation error ratio). This feedback loop enables continuous monitoring and adjustment of delay and offset parameters to maintain accurate phase alignment between the RF signal and modulated supply voltage, thereby resolving the phase alignment accuracy deterioration while preserving efficiency improvements.
Solution Approach 2:
The patent replaces traditional mechanical or analog delay compensation methods with digital signal processing. By converting RF signals to digital domain and using digital algorithms to calculate and adjust delay and offset parameters based on error measures, the system achieves precise phase alignment control without the limitations of analog approaches, thus maintaining both efficiency and measurement precision.
2Measurement precision
If delay and offset adjustments are made to correct phase misalignment, then phase alignment accuracy is improved, but device complexity increases due to additional signal processing requirements
Solution Approach 1:
The patent makes the signal processing unit multi-functional by using it for both error measure calculation (to determine phase alignment accuracy) and delay/offset adjustment (to correct misalignment). Additionally, the same digital domain processing handles both RF signal analysis and envelope signal generation. This consolidation of multiple functions into a single processing unit achieves phase alignment correction without proportionally increasing device complexity.
Solution Approach 2:
The patent introduces digital domain conversion as an intermediary step between the analog RF signal and the delay/offset adjustment process. By converting RF signals to digital domain, the system enables precise measurement and adjustment of phase parameters using digital algorithms, which are more controllable and adjustable than direct analog methods, thus achieving accurate phase alignment with manageable complexity.
3Reliability
If error measures are monitored and adjusted in real-time, then amplifier performance is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent implements dynamic adjustment of delay and offset parameters based on real-time error measure monitoring. Instead of relying on fixed, precision-manufactured components with strict tolerances, the system continuously adapts parameters during operation to compensate for variations and maintain optimal performance. This dynamic approach reduces the stringency of manufacturing precision requirements while ensuring reliable amplifier performance.
Data Source
Figure 1
AI summary
An envelope tracking arrangement (1), comprising: a power transistor (12) for amplification of an RF signal (RF in), a modulator (5) for providing a modulated supply voltage (V) as a dynamic bias voltage to the power transistor (12), the modulated supply voltage (V) being dependent on an envelope signal (signal envelope) of the RF signal (RF in), and a signal processing unit, in particular a digital signal processing unit (6), for comparing at least one error measure of the RF input and output signals (RF in, RF out) of the power transistor (12) in order to perform at least one of a delay adjustment and an offset adjustment between the RF signal (RF in) and the modulated supply voltage (V). The RF input and output signals (RF in, RF out) are preferably tapped in an input coupling unit (C2) at an input of the power transistor (12) and in an output coupling unit (C1) at an output of the power transistor (12), respectively. A corresponding method for performing at least one of a delay adjustment and an offset adjustment is also disclosed.