Envelope Tracking PWM with Dynamic 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 limited output voltage, resulting in ACPR and EVM degradation.
Innovation Solution
A dynamic boosting mechanism is implemented, where a boost circuit generates a higher supply voltage for the envelope tracking modulator when the desired power amplifier supply voltage exceeds a predetermined threshold, allowing the modulator to input either the available or boosted voltage, thereby reducing clipping and distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the battery voltage is used as the supply voltage for the envelope tracking modulator, then the power consumption is reduced and the system is simplified, but the supply voltage is clipped when the desired power amplifier supply voltage exceeds the battery voltage, causing distortion and ACPR degradation
Solution Approach 1:
The system dynamically switches between battery voltage mode and boosted voltage mode based on the desired power amplifier supply voltage requirements. The envelope tracking modulator receives either the battery voltage or a boosted voltage from a voltage boosting circuit, controlled by a voltage selection mechanism that adapts to real-time operating conditions, thereby preventing voltage clipping while maintaining energy efficiency.
2Reliability
If a voltage boosting circuit is always enabled to provide higher supply voltage, then the clipping is eliminated and signal quality is improved, but the power consumption increases and device complexity increases
Solution Approach 1:
The voltage boosting circuit is dynamically controlled and only activated when the desired power amplifier supply voltage exceeds the battery voltage. A voltage selection mechanism monitors the operating conditions and switches between battery voltage mode and boosted voltage mode, ensuring signal quality is maintained while minimizing power consumption by avoiding unnecessary boosting.
Solution Approach 2:
The system changes the supply voltage parameter dynamically based on operating conditions. When high output power is required and the battery voltage is insufficient, the boosting circuit increases the supply voltage parameter; when lower power is sufficient, the system reverts to using the battery voltage directly, thus adapting the voltage parameter to match the actual operational needs.
3Device complexity
If the battery voltage is used as the supply voltage for the envelope tracking modulator, then the device complexity is reduced, but the supply voltage is clipped when maximum output power is required, causing ACPR degradation
Solution Approach 1:
The system employs a dynamic voltage selection mechanism that switches between battery voltage and boosted voltage based on the desired power amplifier supply voltage. This controlled complexity is introduced only when necessary (during high power transmission) to maintain ACPR performance, while keeping the circuit simple during normal operation.
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 solution effectively reduces clipping and distortion, improving the ACPR performance by 4-5 dB, ensuring the power amplifier supply voltage is not limited by the battery voltage, and maintaining acceptable signal quality.
Implementation Method 1
A boost circuit is coupled to the power terminal and configured to generate a boosted supply voltage greater than the available supply voltage
Implementation Method 2
modulating the supply voltage of the power amplifier (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.