Doherty Power Amplifier Envelope Tracking for Efficiency and Linearity
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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 a carrier amplifier, a peaking amplifier, and envelope tracking (ET) circuitry, which generates two modulated supply voltages from a single tracker circuit to control the Doherty power amplifier, enhancing efficiency and linearity.
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 envelope tracking circuitry. The supply voltages are dynamically adjusted according to the instantaneous power demand, allowing the amplifiers to operate efficiently across the entire power range from average to peak power, thereby resolving the energy efficiency deterioration while maintaining power amplification capability.
Solution Approach 2:
The patent changes the operating parameters by modulating the supply voltages of the carrier and peaking amplifiers independently. By varying the supply voltage levels dynamically based on the RF envelope signal, the system optimizes the operating point of each amplifier stage, improving energy efficiency while maintaining the required power amplification capability.
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 dynamic supply voltage modulation through envelope tracking for both carrier and peaking amplifiers. This dynamic control allows the system to maintain optimal operating conditions across varying power levels, preserving linearity by preventing the amplifiers from operating in non-linear regions during transitions between average and peak power output.
Solution Approach 2:
The envelope tracking circuitry provides feedback control by monitoring the RF envelope signal and adjusting the supply voltages of both carrier and peaking amplifiers accordingly. This feedback mechanism ensures that the amplifiers operate within their linear regions, maintaining signal linearity while enabling power amplification capability across the full power range.
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.