Doherty Power Amplifier Envelope Tracking for High-PAPR Efficiency
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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 linearity and overall efficiency in RF communication systems.
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 efficiency and linearity.
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 applies dynamics by transitioning from fixed supply voltage to dynamic envelope tracking that adjusts supply voltage in real-time according to the RF signal envelope. The envelope tracker modifies the supply voltage to the carrier and peaking amplification stages based on the instantaneous power level, enabling the amplifier to maintain high efficiency across varying power conditions while managing the added control complexity.
Solution Approach 2:
The patent implements parameter changes by varying the supply voltage parameter dynamically rather than keeping it fixed. The envelope tracking system changes the supply voltage parameter in response to the RF signal envelope, allowing the Doherty amplifier to operate efficiently at both high and low power levels. This parameter adaptation resolves the contradiction between simplicity and efficiency.
2Use of energy by moving object
If separate supply voltages are provided to carrier and peaking amplification stages, then transmission efficiency is improved, but device complexity increases due to additional envelope tracking circuits and delay circuits
Solution Approach 1:
The patent applies segmentation by dividing the power amplifier into separate carrier and peaking amplification stages, each with its own envelope tracking circuit. This segmentation allows independent optimization of each stage's supply voltage, improving overall efficiency. The delay circuit further segments the control signals to account for phase differences between stages, managing the complexity through structured division.
Solution Approach 2:
The patent introduces an intermediary delay circuit that mediates between the envelope tracker and the peaking amplification stage. This intermediary component compensates for phase delay mismatches by introducing a controlled time delay to the supply voltage signal, enabling coherent operation of the distributed amplification stages while maintaining the efficiency benefits of separate voltage control.
3Loss of energy
If envelope tracking is implemented to improve efficiency, then DC power consumption is reduced, but linearity may be affected due to dynamic supply voltage variations
Solution Approach 1:
The patent implements feedback by using the envelope detector to continuously monitor the RF signal amplitude and adjust the supply voltage accordingly. This closed-loop feedback mechanism ensures that the supply voltage tracks the signal envelope accurately, maintaining both efficiency and linearity. The feedback approach allows dynamic power consumption reduction while preserving signal fidelity through adaptive compensation.
Data Source
AI summary
Envelope tracking schemes for Doherty power amplifiers are provided herein. In certain embodiments, a mobile device includes a Doherty power amplifier that amplifies an RF signal for transmission on an antenna, and an envelope tracker that controls a supply voltage of the Doherty power amplifier based on an envelope of the RF signal amplified by the Doherty power amplifier. Thus, supply modulation is used to control the supply voltage of the Doherty power amplifier to achieve gains in linearity, efficiency, and/or other performance metrics. Furthermore, the Doherty power amplifiers herein can provide higher overall transmission efficiency and/or lower DC power consumption, which in turn leads to lower operating temperatures and/or improved reliability.