Replica-Cell RF Power Amplifier for Stable Stepwise Output Control
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Solution Overview
Problem
Existing RF power amplifier control techniques are sensitive to temperature, manufacturing process tolerances, and power supply voltage variations, which affects the reliability and accuracy of output power control.
Innovation Solution
A power amplifier design that controls DC current in a replica device and uses parallel cells to achieve stepwise power control, with a power controller selecting combinations of amplifier cells and adjusting voltage and current references to maintain consistent output power levels, minimizing the impact of temperature and voltage variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional power amplifier control techniques (gate/base drive control, bias current adjustment) are used, then output power control is achieved, but the system becomes sensitive to temperature, manufacturing process tolerances and power supply voltage variations
Solution Approach 1:
The patent uses a replica device that copies the electrical characteristics of the power amplifier device. By measuring and controlling the replica device instead of the actual power amplifier, the system achieves accurate power control while being isolated from temperature and voltage variations affecting the main device.
Solution Approach 2:
The replica device acts as an intermediary between the control circuitry and the actual power amplifier. It serves as a mediator that translates control signals into accurate power levels while compensating for environmental variations, thereby improving reliability without sacrificing power control capability.
2Power
If gate or base drive control methods are used, then power control is achieved, but manufacturing process tolerances affect the accuracy and reliability of control
Solution Approach 1:
The replica device is designed to replicate the exact electrical characteristics and manufacturing variations of the power amplifier device. By controlling the replica rather than the actual device directly, the system compensates for manufacturing tolerances and achieves consistent power control accuracy across different production batches.
3Power
If bias current adjustment is used for power control, then output power can be regulated, but the system becomes sensitive to power supply voltage variations
Solution Approach 1:
The replica device serves as an intermediary that isolates the power control function from power supply voltage variations. By measuring and controlling the replica device with stable reference voltages, the system achieves accurate power regulation while being immune to fluctuations in the main power supply voltage affecting the actual amplifier.
Data Source
Figure 1
Figure 2~3
AI summary
A power amplifier comprises an amplifier core including parallel amplifier cells, a replica cell made of one amplifier cell similar to those of the amplifier core, a power controller to select a combination of amplifier cells to activate, a regulator to fix the top voltage of the replica cell to a reference voltage, a voltage generator to provide the voltage reference to the regulator, a current generator to provide a reference current through the replica cell, and a drive unit controlled by the regulator output to drive the combination of amplifier cells, wherein each selected combination of activated cells defines a predetermined attenuation level of power amplifier output signal so that it is attenuated in a stepwise manner.