Single-Supply Multi-Level Envelope Tracker for RF Power Amplifiers
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Solution Overview
Problem
Current RF power amplifiers in telecommunications and radar applications face inefficiencies due to the need for multiple voltage sources and complex hardware in multi-level envelope tracking, which increases hardware complexity and losses, especially in achieving high-resolution voltage discretization and dynamic impedance loads.
Innovation Solution
A single-supply multi-level supply modulator using flying capacitors and a switch network with digital pre-distortion (DPD) to generate variable DC voltage levels, eliminating the need for multiple external supplies and simplifying the design by using a feedback loop to regulate the capacitors and maintain balanced voltage levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If multiple discrete voltage sources are used for multi-level envelope tracking, then back-off efficiency is improved, but hardware complexity increases due to additional voltage supplies
Solution Approach 1:
The patent merges multiple voltage supply functions into a single voltage source by using a multi-level converter that generates multiple discrete voltage levels (Vdc, Vdc/2, Vdc/4, 0V) from one input supply. This eliminates the need for multiple independent voltage sources while maintaining the efficiency benefits of multi-level operation.
Solution Approach 2:
The single voltage source is designed to perform multiple functions by generating different voltage levels through the multi-level converter architecture. The converter can output various discrete levels to match the RF amplifier's voltage requirements, making one supply source universally capable of replacing multiple specialized supplies.
2Measurement precision
If multiple external voltage supplies are used for high-resolution voltage discretization, then voltage precision is improved, but losses increase due to multiple power converters
Solution Approach 1:
The patent combines multiple power conversion functions into a single multi-level converter, eliminating the need for multiple separate power converters. This single converter achieves high-resolution voltage discretization by generating multiple precise voltage levels (Vdc, Vdc/2, Vdc/4, 0V) from one input, thereby reducing cumulative losses while maintaining voltage precision.
3Device complexity
If a single DC supply is used instead of multiple supplies, then hardware complexity is reduced, but achieving multiple output levels becomes more difficult
Solution Approach 1:
The patent segments the voltage output into multiple discrete levels (Vdc, Vdc/2, Vdc/4, 0V) using a multi-level converter architecture. This segmentation allows a single supply to provide differentiated voltage levels that match the RF amplifier's requirements, maintaining adaptability while simplifying the supply structure.
Solution Approach 2:
The multi-level converter dynamically switches between different voltage levels based on the RF amplifier's instantaneous power requirements. This dynamic voltage adjustment capability enables a single supply to adapt to varying output level demands, maintaining versatility without requiring multiple fixed voltage sources.
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 solution enhances back-off efficiency and reduces hardware complexity by achieving multiple output levels with a single DC supply, improving power amplifier efficiency and linearity while minimizing ripple and circuit cost, with up to 55% drain efficiency and 14 percentage points improvement in linearity for radar waveforms.
Implementation Method 1
A single DC voltage supply along with (for example) two flying capacitors provides capability for four output voltage levels
Implementation Method 2
A single-supply multi-level supply modulator using flying capacitors and a switch network with digital pre-distortion (DPD) to generate variable DC voltage levels
Implementation Method 3
A feedback loop can be implemented with an DSP/FPGA to ensure the floating capacitors maintain their chosen voltage (for each output level) with only a small amount of ripple
Data Source
AI summary
A multi-level supply modulator for RF power amplifiers requires only a single independent voltage supply along with one or more flying capacitors to achieve multiple output levels. The flying capacitor is used to store the intermediate voltage level between the DC supply level and ground. A switch network is connected between the DC voltage supply and the power amplifier and is configured to provide power at variable, discrete DC voltages, for example the DC voltage supply level, ground, and a level halfway between the DC voltage supply level and ground. The flying capacitor is connected to switches in the switch network, and a sensing circuit detects the voltage across the flying capacitor and generates a feedback signal. Control circuitry controls the switch network (and thus the power supplied to the amplifier) based on the feedback signal.