Distributed Feed-Forward Envelope Tracking for RF Power Amplifiers
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Solution Overview
Problem
Existing envelope tracking techniques for power amplifiers in transmitters face challenges in scaling for high-frequency applications and carrier aggregation, particularly due to the complexity of analog control loops and large solution areas on printed circuit boards.
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 selector circuitry to select the appropriate voltage levels based on a target envelope signal, thereby improving accuracy and reducing load dependency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If analog control loop is used for envelope tracking, then power amplifier efficiency is improved, but device complexity and solution area increase
Solution Approach 1:
The patent replaces the analog control loop (electrical/mechanical system) with a digital feedforward DAC-based envelope tracking system. The analog voltage control is substituted with digital signal processing and digital-to-analog conversion, eliminating the need for complex analog control circuitry while maintaining power amplifier efficiency.
Solution Approach 2:
The patent extracts and removes the analog control loop from the envelope tracking system, replacing it with a digital feedforward approach. By taking out the problematic analog control components, the system achieves simplified architecture while preserving the power efficiency benefits.
2Loss of energy
If analog control loop is used for envelope tracking, then power amplifier efficiency is improved, but solution area on printed circuit board increases
Solution Approach 1:
The digital feedforward DAC-based system replaces the space-consuming analog control loop components with integrated digital circuitry and compact DAC architecture, significantly reducing the printed circuit board area while maintaining power amplifier efficiency.
3Device complexity
If feedforward DAC circuitry is used, then device complexity is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The feedforward DAC circuitry pre-generates the exact supply voltage levels needed based on the modulated signal envelope, eliminating the need for real-time analog control adjustments. This preliminary digital-based voltage generation simplifies the overall device complexity while the precision is maintained through digital accuracy.
4Adaptability or versatility
If distributed feedforward DAC is implemented, then adaptability for high-frequency and carrier aggregation is improved, but device complexity increases
Solution Approach 1:
The distributed feedforward DAC architecture segments the envelope tracking function across multiple independent DAC units, each handling specific frequency bands or carrier aggregations. This segmentation improves adaptability for high-frequency and carrier aggregation applications while the modular nature actually reduces overall system complexity compared to a single complex analog control loop.
Data Source
AI summary
Systems, methods, and circuitries are provided for generating a power amplifier supply voltage based on a target envelope signal for a radio frequency (RF) transmit signal. An envelope tracking system includes a first selector circuitry and predistortion circuitry. The first selector circuitry is disposed in a selector module and is configured to input a plurality of voltages conducted on a first plurality of power lanes, wherein the first plurality of power lanes is part of a power distribution network; select a voltage from the plurality of voltages based on the target envelope signal; and provide the selected voltage to a supply lane connected to an input of the power amplifier that amplifies the RF transmit signal. The predistortion circuitry is configured to modify the RF transmit signal based on a selected power lane of the first plurality of power lanes that conducts the selected voltage.