Multi-Carrier Power Tracking Supply for RF Amplifier Efficiency
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Solution Overview
Problem
Wireless devices face inefficiencies in generating power supply voltages for power amplifiers that process multiple transmit signals simultaneously, leading to wasted power and potential intermodulation distortion due to the power supply voltage not tracking the envelope of the output RF signal.
Innovation Solution
A power tracking system that determines a power tracking signal based on the in-phase and quadrature components of multiple transmit signals, generating a power supply voltage to match the envelope of the output RF signal, either using separate power amplifiers for each signal or a single power amplifier with power tracking for all signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed power supply voltage is used for the power amplifier, then the circuit design is simple, but the power-added efficiency is reduced and power consumption increases
Solution Approach 1:
The power supply voltage is changed from a fixed static value to a dynamic value that varies with the envelope of the RF signal. The power tracker generates a time-varying power supply voltage that follows the signal envelope, allowing the power amplifier to operate efficiently across different power levels while maintaining relatively simple circuit architecture.
Solution Approach 2:
A feedback mechanism is implemented where the envelope of the RF signal is detected and used to control the power supply voltage. The power tracker monitors the signal envelope and adjusts the power supply voltage accordingly, creating a closed-loop system that optimizes efficiency without significantly increasing circuit complexity.
2Device complexity
If a fixed power supply voltage is used for the power amplifier, then the power supply circuit is simple, but power consumption increases due to wasted power
Solution Approach 1:
The power supply voltage transitions from a constant fixed value to a dynamic variable that adapts to the RF signal envelope. This dynamic adjustment ensures the power amplifier receives only the necessary power at each moment, dramatically reducing wasted power while the power tracker circuit maintains reasonable complexity through efficient envelope detection and voltage generation.
3Device complexity
If a fixed power supply voltage is used, then the circuit implementation is straightforward, but intermodulation distortion occurs
Solution Approach 1:
The power supply voltage is made dynamic to track the RF signal envelope, allowing the power amplifier to maintain optimal operating conditions across varying signal levels. This dynamic power supply prevents the amplifier from entering saturation or compression regions that cause intermodulation distortion, while the overall circuit implementation remains relatively straightforward through the use of envelope detection and voltage follower circuits.
Data Source
AI summary
Techniques for generating a power tracking supply voltage for a circuit (e.g., a power amplifier) are disclosed. The circuit may process multiple transmit signals being sent simultaneously on multiple carriers at different frequencies. In one exemplary design, an apparatus includes a power tracker and a power supply generator. The power tracker determines a power tracking signal based on inphase (I) and quadrature (Q) components of a plurality of transmit signals being sent simultaneously. The power supply generator generates a power supply voltage based on the power tracking signal. The apparatus may further include a power amplifier (PA) that amplifies a modulated radio frequency (RF) signal based on the power supply voltage and provides an output RF signal.