Envelope Tracking PWM Boosting to Prevent PA Supply Clipping
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Solution Overview
Problem
In wireless communication terminals, envelope tracking modulators face clipping issues when the desired power amplifier supply voltage exceeds the available battery voltage, leading to distortion and degradation of the transmitted signal due to ACPR and EVM degradation.
Innovation Solution
A dynamic boosting system that selectively switches between the available battery voltage and a boosted voltage supply to the envelope tracking modulator, ensuring the power amplifier receives a sufficient supply voltage, thereby reducing clipping and distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the ET modulator operates with battery voltage as input supply, then power consumption is reduced, but the PA supply voltage is clipped when desired voltage exceeds battery voltage
Solution Approach 1:
The system dynamically switches between battery voltage and boosted voltage supply to the ET modulator based on the magnitude of the envelope signal. When the envelope magnitude exceeds a threshold indicating potential clipping, the system activates the boosted supply path to provide sufficient voltage headroom, thereby preventing signal distortion while maintaining energy efficiency during normal operation
Solution Approach 2:
The system changes the input supply voltage parameter to the ET modulator based on operating conditions. By monitoring the envelope signal magnitude and switching between two voltage supply modes (battery voltage and boosted voltage), the system adapts the supply voltage parameter to prevent clipping while minimizing energy consumption during normal operation
2Reliability
If a supplemental power supply is activated to provide boosted voltage, then clipping is reduced, but system complexity increases
Solution Approach 1:
A voltage selector circuit acts as an intermediary component that switches between the battery voltage and the boosted voltage from the supplemental power supply. This mediator selectively connects the appropriate voltage source to the ET modulator based on the envelope signal magnitude, enabling clipping prevention without requiring complete system redesign
Solution Approach 2:
The power supply system is segmented into two independent voltage sources: the primary battery voltage supply and the supplemental boosted voltage supply. The voltage selector circuit divides the operation into two modes, activating only the necessary supply path based on real-time envelope signal conditions, thereby reducing unnecessary complexity
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
The dynamic boosting system significantly improves ACPR performance by preventing clipping, maintaining signal quality, and reducing linearity degradation, with minimal efficiency loss.
Implementation Method 1
a pulse width modulation, PWM, generator configured to receive the envelope signal and configured to generate a PWM signal based on the envelope signal
Implementation Method 2
modulating the supply voltage input to the PA in such a way as to follow the envelope of the transmitted signal allows the PA to be operated at a higher efficiency
Data Source
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AI summary
A system, apparatus and method is described for dynamically boosting (increasing) the power supply voltage to an envelope tracking (ET) modulator within a transmitter system when the target/desired power amplifier voltage supply is above a predetermined threshold (e.g., equal to the available power supply of the system, such as a battery). By boosting the power input supply to the ET modulator, the modulated power supply provided to the power amplifier (PA) is also increased. This reduces or eliminates clipping that normally occurs when the target/desired PA supply voltage is greater than the available power supply voltage and reduces distortion in the transmitted signal.