Envelope Tracking Power Supply for RF Amplifier Back-Off Loss
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Solution Overview
Problem
Power amplifiers in wireless base stations consume significant power, leading to increased operational costs and decreased efficiency due to the need for linear power amplification, which often requires RF power amplifiers to operate in a 'backed off' state, reducing overall efficiency.
Innovation Solution
An efficient envelope tracking power supply dynamically adjusts the supply voltage of power amplifiers to maintain linear operation while maximizing efficiency, using a current-controlled switching converter and a linear amplifier to provide DC and AC power, respectively, allowing the amplifiers to operate close to saturation without losing linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If linear power amplification is used to maintain signal linearity, then modulation accuracy is improved, but power consumption increases and efficiency decreases
Solution Approach 1:
The patent applies dynamics by making the power amplifier's operating point variable through envelope tracking. The supply voltage dynamically follows the envelope of the modulating signal, allowing the amplifier to operate at optimal efficiency points while maintaining linearity when needed. This resolves the contradiction by enabling the amplifier to adapt its operating state rather than being fixed in a less efficient backed-off state.
Solution Approach 2:
The patent changes the supply voltage parameter dynamically to match the signal envelope. By varying the DC supply voltage in proportion to the modulating signal envelope, the system maintains the amplifier in a linear operating region only when necessary, significantly improving overall power efficiency while preserving modulation accuracy.
2Measurement precision
If RF power amplifiers operate in a 'backed off' state to maintain linearity, then modulation accuracy is improved, but overall system efficiency decreases
Solution Approach 1:
The envelope tracking system dynamically adjusts the supply voltage to allow the amplifier to operate near saturation when signal power is high, rather than being permanently backed off. This dynamic operation maintains linearity when needed while maximizing efficiency during low-power periods, resolving the productivity efficiency issue.
Solution Approach 2:
The power supply system automatically adjusts itself to provide optimal voltage based on the signal envelope, enabling the amplifier to self-regulate its operating point. This eliminates the need for fixed backed-off operation and allows the system to achieve high efficiency while maintaining linearity through the intelligent power supply control.
Data Source
AI summary
An apparatus includes an envelope tracking power supply configured to control a power amplifier. The power supply includes a first amplifier configured to receive an input voltage and generate a supply voltage for the power amplifier. The power supply also includes a second amplifier configured to receive a shifted input voltage. An output of the second amplifier is coupled to the first amplifier. The first amplifier is configured to maintain an operational mode of the power amplifier. The power supply could further include a third amplifier. An output of the third amplifier is coupled to an input of the second amplifier, and the third amplifier is configured to receive a second shifted input.