Dual Envelope Tracking in Doherty Power Amplifiers
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Solution Overview
Problem
Existing Doherty-type power amplifiers in radio frequency transmitters face challenges in achieving high energy efficiency and linearity during power amplification.
Innovation Solution
The implementation of a power amplifier system with envelope tracking (ET) circuitry, which includes a carrier amplifier, a peaking amplifier, and ET circuitry with dual instantaneous voltage enhanced rapid tracking (DiVeRT) capabilities, allowing for separate modulated supply voltages for the carrier and peaking amplifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a Doherty amplifier uses a carrier amplifier and peaking amplifier to operate at voltages between average power and peak power, then power amplification capability is improved, but energy efficiency deteriorates
Solution Approach 1:
The patent implements dynamic supply voltage modulation for both carrier and peaking amplifiers using separate envelope tracking circuits. The supply voltages are dynamically adjusted based on real-time operating conditions, allowing the amplifiers to maintain optimal efficiency across different power levels while preserving the Doherty configuration's power amplification capability.
Solution Approach 2:
The patent segments the power amplification function into carrier amplifier and peaking amplifier stages, each with independent envelope tracking circuits. This segmentation allows separate optimization of supply voltages for each stage, enabling the carrier amplifier to operate efficiently at average power while the peaking amplifier activates only when needed for peak power, thus resolving the efficiency contradiction.
2Power
If a Doherty amplifier uses a carrier amplifier and peaking amplifier to operate at voltages between average power and peak power, then power amplification capability is improved, but linearity deteriorates
Solution Approach 1:
The patent employs feedback mechanisms in the envelope tracking circuits that monitor the operating voltages and currents of both carrier and peaking amplifiers. This feedback enables real-time adjustment of supply voltages to compensate for non-linearities, maintaining signal linearity across the full power range while preserving the power amplification benefits of the Doherty configuration.
Solution Approach 2:
The patent dynamically changes the supply voltage parameters for both carrier and peaking amplifiers based on the instantaneous power level. By adjusting these parameters in real-time, the system maintains optimal operating conditions for linearity across different power levels, resolving the contradiction between power amplification capability and signal linearity.
Data Source
AI summary
A power amplifier system having a carrier amplifier having a first supply node, a peaking amplifier having a second supply node, and envelope tracking (ET) circuitry is disclosed. The ET circuitry has a first tracking amplifier that generates a first voltage signal at the first supply node, a second tracking amplifier that generates a second voltage signal at the second supply node, and a transistor coupled between the first supply node and the second supply node. A control circuit has a first input coupled to an output of both or either of the first tracking amplifier and the second tracking amplifier and a control output terminal coupled to a control input terminal of the transistor, wherein the control circuit is configured to progressively turn on the transistor to pass current from the first supply node to the second supply node as the peaking amplifier progressively becomes active.