Digital Envelope Tracking with Smooth Voltage Transitions for RF PAs
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Solution Overview
Problem
Conventional digital envelope tracking methods using constant voltage levels in RF power amplifiers are inefficient for mobile applications, as they lead to disruptions and increased error vector magnitude due to frequent power level changes, and accelerating voltage switching results in overshoots and ringing, degrading RF signal performance.
Innovation Solution
Implementing a system with dynamically changing supply voltage levels that gradually transition from one set to another, using a setpoint generator and voltage regulator to control the transition, ensuring continuous RF signal output and maintaining efficiency without interruptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the switching speed from one set of voltages to another is accelerated, then the response time improves, but overshoots and ringing occur which degrade RF signal performance
Solution Approach 1:
The patent applies preliminary action by predicting future RF envelope peaks in advance and proactively adjusting voltage levels before the actual power changes are needed. The controller performs forward-looking analysis of the RF envelope to identify upcoming peaks, allowing the voltage to be adjusted in advance rather than reactively. This prevents the need for rapid voltage switching that would cause overshoots and ringing, while still maintaining efficient power amplifier operation.
2Loss of energy
If a greater number of voltage levels is used, then the efficiency of the power amplifier improves, but the complexity of the tracker increases due to additional external capacitors
Solution Approach 1:
The patent applies dynamics by transitioning from static, discrete voltage levels to dynamic, continuously adjustable voltage levels. Instead of using multiple fixed voltage levels that require separate capacitors for each level, the system uses a single capacitor that can be dynamically charged to any required voltage level. The voltage regulator can continuously adjust the voltage within a range, providing the same or better efficiency improvement as multiple discrete levels but with reduced hardware complexity.
Solution Approach 2:
The patent changes the parameter of voltage from discrete, fixed values to continuous, adjustable values. By allowing the voltage to vary continuously rather than being constrained to predefined levels, the system achieves fine-grained control over power amplifier efficiency without requiring additional capacitors for each voltage level. This parameter change enables a single capacitor to replace multiple capacitors while maintaining or improving efficiency.
3Device complexity
If conventional constant voltage levels are used, then the tracker design is simpler, but mobile applications suffer from disruptions and increased error vector magnitude during power level changes
Solution Approach 1:
The patent applies preliminary action by performing forward-looking analysis of the RF envelope to predict future power requirements. The controller identifies upcoming peaks in advance and proactively adjusts voltage levels before the power changes are needed, ensuring smooth transitions without disruptions. This predictive approach maintains signal continuity while keeping the tracker design relatively simple, avoiding the need for complex rapid-switching hardware.
Solution Approach 2:
The patent introduces dynamic voltage adjustment capability that allows smooth transitions between voltage levels. Instead of abrupt switching between constant voltage levels, the voltage regulator continuously adjusts the voltage to match the predicted power requirements. This dynamic approach ensures output signal continuity during transitions while maintaining a manageable level of design complexity through the use of a single adjustable capacitor rather than multiple fixed capacitors.
Data Source
AI summary
A device for digital envelope tracking with dynamically changing voltage levels for a radio frequency (RF) power amplifier is disclosed. A power management unit generates a set of supply voltages for a power amplifier based on a control signal. A setpoint generator in the power management integrated circuit gradually increases or decreases a target voltage such that the set of supply voltages output from the voltage converter gradually increase or decrease in response to a gradual transition of the target voltage. A transceiver includes digital models for replicating a behavior of the setpoint generator and a voltage regulator in the voltage converter such that a signal pre-distortion unit may use an instantaneous voltage level for signal predistortion.