Feed-forward DAC Envelope Tracking for RF Power Amplifiers
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Solution Overview
Problem
Existing envelope tracking systems for power amplifiers in transmitters face challenges in scaling for high frequency applications and maintaining efficiency due to the complexity of analog control loops and large solution areas on printed circuit boards, especially with increasing carrier aggregation in cellular and WLAN/WiFi applications.
Innovation Solution
The implementation of a feed forward digital to analog converter (DAC) circuitry that generates power amplifier supply voltages in a feed-forward manner, eliminating the need for an analog control loop and using a voltage source circuitry with a single-inductor-multiple-output (SIMO) DCDC converter to produce multiple voltage levels, which are then selected by a selector circuitry based on a target envelope signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If an analog control loop is used for envelope tracking, then the power amplifier efficiency is improved, but the device complexity and solution area increase
Solution Approach 1:
The patent replaces the analog control loop (electrical/mechanical system) with a digital feed-forward DAC-based envelope tracking system. The digital system uses a digital-to-analog converter to generate the envelope signal directly from digital baseband signals, eliminating the need for complex analog components such as voltage-controlled amplifiers, phase-locked loops, and analog modulators. This substitution maintains power amplifier efficiency while significantly reducing device complexity and PCB area.
2Loss of energy
If an analog control loop is used for envelope tracking, then the power amplifier efficiency is improved, but the solution area on printed circuit board increases
Solution Approach 1:
The patent replaces the analog control loop (electrical/mechanical system) with a digital feed-forward DAC-based envelope tracking system. The digital system uses a digital-to-analog converter to generate the envelope signal directly from digital baseband signals, eliminating the need for complex analog components such as voltage-controlled amplifiers, phase-locked loops, and analog modulators. This substitution maintains power amplifier efficiency while significantly reducing device complexity and PCB area.
3Loss of energy
If conventional envelope tracking is used, then efficiency is improved, but scaling for high frequency applications becomes difficult
Solution Approach 1:
The patent implements a dynamic feed-forward DAC-based envelope tracking system that adapts to high frequency applications. The system dynamically generates the envelope signal by processing digital baseband signals through a DAC, allowing it to respond rapidly to signal variations. This dynamic approach enables the system to scale to high frequencies where conventional analog control loops fail due to bandwidth limitations and phase margin issues.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach achieves efficient envelope tracking that scales for higher frequencies, reduces load dependency, and provides a compact solution with improved accuracy and efficiency, especially at high frequencies, while suppressing resonant settling and maintaining low power consumption.
Implementation Method 1
voltage source circuitry with a single-inductor-multiple-output (SIMO) DCDC converter to produce multiple voltage levels
Data Source
AI summary
An envelope tracking system for controlling a power amplifier supply voltage includes envelope circuitry and a feed forward digital to analog converter (DAC) circuitry. The envelope circuitry is configured to generate a target envelope signal based on a selected power amplifier supply voltage. The feed forward DAC circuitry includes a voltage source circuitry and a selector circuitry. The voltage source circuitry is configured to generate a plurality of voltages. The selector circuitry is configured to select one of the plurality of voltages based at least on the target envelope signal. The feed forward DAC circuitry is configured to provide the selected voltage to a supply voltage input of a power amplifier that amplifies a radio frequency (RF) transmit signal.