Envelope-Tracking RF Transmitter Gain Linearity at Low Power
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Solution Overview
Problem
Mobile communication devices face challenges in maintaining high power efficiency and linearity in gain, especially in low output power regions due to increased peak-to-average power ratio (PAPR) in high-speed data communication standards, which leads to higher power consumption and deterioration of linearity.
Innovation Solution
A transmission unit is designed with a power supply circuit that adjusts the power supply voltage based on the amplitude level of the RF signal, and an attenuator that increases signal attenuation when the power supply voltage is below a certain level, preventing gain increase in low output power regions and enhancing linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high power supply voltage is used to maintain high linearity in high-PAPR situations, then linearity is improved, but power consumption increases
Solution Approach 1:
The power supply voltage is dynamically adjusted according to the amplitude level of the modulated signal through envelope tracking. The power supply circuit changes the power supply voltage in real-time based on signal characteristics, allowing the amplifier to operate at lower voltages during low-amplitude periods while maintaining high voltage during peak periods, thus improving power efficiency while preserving linearity when needed.
Solution Approach 2:
The invention changes the power supply voltage parameter dynamically to match signal amplitude requirements. By adjusting the voltage parameter according to signal conditions, the system achieves optimal trade-off between linearity and power consumption, avoiding the need to maintain high voltage continuously.
2Use of energy by moving object
If the power supply voltage is reduced in low output power regions to improve power efficiency, then power efficiency is improved, but gain increases causing deterioration of linearity
Solution Approach 1:
An attenuator is introduced as an intermediary component between the signal source and the power amplifier. The attenuator reduces the amplitude of the input signal in low output power regions, compensating for the excessive gain that occurs when the power supply voltage is reduced. This allows the system to maintain both power efficiency and linearity by mediating the signal level.
Solution Approach 2:
The attenuator applies preliminary attenuation to the input signal before it enters the power amplifier stage. By reducing the signal amplitude in advance, the system prevents the gain increase from causing linearity deterioration, effectively counteracting the adverse effect before it manifests in the output.
Data Source
AI summary
A transmission unit includes a first transistor that amplifies power of a first signal and outputs a second signal, a power supply circuit that supplies to the first transistor a power supply voltage that changes in accordance with an amplitude level of the first signal, and an attenuator that attenuates the first signal in such a manner that an amount of attenuation of the first signal increases with a decrease in the power supply voltage when the power supply voltage is less than a first level.