Doherty Power Amplifier Envelope Tracking With Delayed Peaking Supply
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Solution Overview
Problem
Conventional Doherty power amplifiers operate with fixed supply voltages, leading to inefficiencies at lower power levels and high peak-to-average ratio waveforms, especially when output power is not well-centered in their efficiency profile, which affects the linearity and efficiency of RF signal amplification in communication systems like 5G NR.
Innovation Solution
Implementing an envelope tracking system that controls the supply voltage of the Doherty power amplifier based on the envelope of the RF signal, using separate envelope tracking circuits for the carrier and peaking amplification stages, and a delay circuit to compensate for phase delay mismatches between stages, allowing for dynamic adjustment of supply voltages to enhance linearity and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fixed supply voltage is used in Doherty power amplifier, then device complexity is reduced, but transmission efficiency deteriorates at lower power levels and high peak-to-average ratio waveforms
Solution Approach 1:
The patent implements dynamic supply voltage control for the Doherty power amplifier stages. The carrier amplification stage and peaking amplification stage are supplied with dynamically adjusted voltages based on the envelope of the RF signal, allowing the amplifier to maintain high efficiency across varying power levels rather than operating with fixed supply voltage.
Solution Approach 2:
The patent changes the supply voltage parameter dynamically according to the signal envelope. By adjusting the supply voltage levels of the carrier and peaking stages based on the instantaneous power level, the system optimizes transmission efficiency without requiring overly complex control mechanisms.
2Use of energy by moving object
If separate supply voltages are used for carrier and peaking amplification stages, then transmission efficiency is improved, but device complexity increases
Solution Approach 1:
The patent segments the power supply control into separate envelope tracking circuits for the carrier amplification stage and peaking amplification stage. This allows independent optimization of each stage's supply voltage while maintaining manageable complexity through modular circuit design.
Solution Approach 2:
The patent applies different supply voltage characteristics to different stages locally. The carrier stage receives a first supply voltage and the peaking stage receives a second supply voltage, each optimized for its specific operational requirements, improving overall transmission efficiency.
3Reliability
If envelope tracking is implemented, then linearity is improved, but DC power consumption increases
Solution Approach 1:
The patent applies envelope tracking selectively to the carrier and peaking stages rather than uniformly across all operating conditions. By using separate envelope tracking circuits that can be independently controlled, the system achieves improved linearity while minimizing unnecessary DC power consumption during different operational modes.
Data Source
AI summary
Envelope tracking schemes for Doherty power amplifiers are provided herein. In certain embodiments, an envelope tracking system includes a carrier amplifier that amplifies a first radio frequency signal, a peaking amplifier that amplifies a second radio frequency signal corresponding to a delayed version of the first radio frequency signal, an envelope tracker that generates a first power supply voltage that powers the carrier amplifier, and a delay circuit that delays the first power supply voltage to generate a second power supply voltage that powers the peaking amplifier. The envelope tracker controls a voltage level of the first power supply voltage to track an envelope of the first radio frequency signal. Thus, supply modulation is used to achieve gains in linearity, efficiency, and/or other performance metrics.