Power Amplifier Supply Voltage Switching for RF Linearity
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Solution Overview
Problem
Conventional wireless communication systems face efficiency issues due to the need for substantial power back-off in power amplifiers to maintain linearity, leading to reduced battery life in portable devices.
Innovation Solution
An envelope tracking technique that adjusts the drain supply voltage of the power amplifier based on the RF signal's envelope, using a detector and controller to switch between a supply voltage and a boosted voltage, optimizing power usage without requiring a continuously variable DC-to-DC converter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If substantial power back-off is applied to maintain linearity in the power amplifier, then linearity is improved, but efficiency deteriorates significantly
Solution Approach 1:
The patent applies dynamics by making the supply voltage to the power amplifier dynamic rather than static. The supply voltage is modulated to track the envelope of the RF signal, allowing the amplifier to operate efficiently across varying power levels while maintaining linearity when needed. This is achieved through an envelope detector that extracts the signal envelope and a voltage modulator that adjusts the supply voltage accordingly.
Solution Approach 2:
The patent changes the parameter of supply voltage from a constant value to a time-varying parameter that follows the signal envelope. By modifying the supply voltage parameter dynamically, the system achieves both high efficiency at low power levels and adequate linearity at high power levels, resolving the contradiction between these two requirements.
2Loss of energy
If power back-off is reduced to improve efficiency, then efficiency is improved, but linearity deteriorates
Solution Approach 1:
The patent applies local quality by providing different supply voltage conditions to different portions of the signal envelope. When the signal envelope is low, a reduced supply voltage is provided for high efficiency. When the signal envelope approaches peak levels, the supply voltage is increased to maintain linearity. This localized adaptation of supply voltage quality resolves the contradiction between efficiency and linearity.
3Loss of energy
If a continuously variable DC-to-DC converter is used to optimize efficiency, then efficiency is improved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the continuous voltage regulation function into discrete components: an envelope detector that extracts signal characteristics, a voltage modulator that generates the supply voltage waveform, and a storage element that maintains voltage during peaks. This segmented approach achieves efficient power amplification without requiring a complex continuously variable DC-to-DC converter.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances amplifier efficiency by providing sufficient voltage only when needed, reducing power consumption and extending battery life in portable devices while maintaining linearity.
Implementation Method 1
providing a boosted voltage as the drain supply voltage when the lowest occurring voltage extreme of the envelope becomes less than the predetermined voltage level by turning off the switching transistor and connecting the charge storage capacitor between the supply voltage source and the output transistor, the boosted voltage including the supply voltage plus the voltage boost value previously stored in the charge storage capacitor
Data Source
AI summary
An apparatus for controlling a power amplifier configured to amplify radio frequency (RF) signal includes a detector and a controller. The detector is configured to detect a power level of the RF signal with respect to a predetermined power threshold and to generate a corresponding detection signal. The controller is configured to provide a control voltage to an output transistor of the amplifier based on the detection signal. The control voltage has a low voltage value, which is substantially the same as a value of a supply voltage, when the detection signal indicates that the power level is below the power threshold, and the control voltage has a high voltage value when the detection signal indicates that the power level is above the power threshold. The controller generates the high voltage value by boosting the supply voltage.