Envelope Shaping in ET Power Amplifiers for OFDM Linearity
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Solution Overview
Problem
Envelope Tracking (ET) Power Amplifiers (PAs) used in conjunction with Orthogonal Frequency Division Multiplexing (OFDM) signals face efficiency and linearity issues due to high Peak-to-Average Power Ratio (PAPR) characteristics, leading to poor performance and unpredictable distortions.
Innovation Solution
The method involves performing envelope shaping on reference envelope signals in the time domain, followed by signal quality control in the frequency domain to reduce PAPR and improve efficiency, using techniques such as de-trough shaping and corrective signal processing to maintain signal quality and linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If envelope tracking is applied to OFDM system to enhance PA efficiency, then power amplifier efficiency is improved, but signal linearity and EVM performance deteriorate due to high PAPR characteristics
Solution Approach 1:
The patent applies preliminary action by performing envelope shaping on the envelope signal before it is used to control the PA power supply. The shaping operation modifies the envelope signal in advance to prevent excessive PAPR from causing distortion, thereby maintaining both efficiency and linearity. This is achieved through time-domain shaping and frequency-domain quality control operations that prepare the envelope signal beforehand.
Solution Approach 2:
The patent employs parameter changes by modifying the envelope signal characteristics through shaping operations. The envelope signal parameters (amplitude, timing) are adjusted to reduce PAPR while maintaining the desired power amplification. The frequency domain quality control further adjusts spectral parameters to ensure signal linearity requirements are met.
2Loss of energy
If power supply voltage is constantly adjusted to ensure peak efficiency, then PA efficiency is improved, but PA operating point changes dramatically causing gain collapse and unpredictable distortions
Solution Approach 1:
The patent applies preliminary action by pre-shaping the envelope signal to prevent extreme variations before they occur. The shaping operation smooths out rapid transitions and limits the range of power supply voltage changes, thereby preventing the PA from entering unstable operating regions. This proactive approach maintains operating stability while preserving efficiency benefits.
Solution Approach 2:
The patent implements beforehand cushioning by introducing smoothing and limiting operations on the envelope signal that cushion against abrupt changes. The frequency domain quality control acts as a buffer that prevents harmful spectral components from causing instability, thereby protecting the PA from gain collapse and unpredictable distortions.
3Loss of energy
If envelope shaping operation is performed on reference envelope signals in time domain, then PAPR is reduced and efficiency is improved, but signal quality may deteriorate requiring frequency domain control
Solution Approach 1:
The patent merges time-domain envelope shaping with frequency-domain quality control into a unified envelope signal processing system. The time-domain shaping reduces PAPR for efficiency, while the frequency-domain control restores and maintains signal quality. Both operations work together synergistically to achieve both efficiency improvement and signal quality preservation simultaneously.
Solution Approach 2:
The patent implements feedback by using the frequency domain quality control to monitor and correct the output of the time-domain shaping operation. The quality control measures signal quality metrics and adjusts the envelope signal accordingly to compensate for any degradation caused by shaping, thereby maintaining overall signal quality while preserving efficiency gains.
Data Source
AI summary
The subject matter described herein relates to envelope shaping in envelope tracking power amplification. A method, apparatus and computer storage medium are provided for envelope shaping in envelope tracking power amplification. In an embodiment, the method comprises performing an envelope shaping operation on reference envelope signals in a time domain to obtain shaped envelope signals; performing a signal quality control on the shaped envelope signals in a frequency domain; and converting the shaped envelope signals from the frequency domain into the time domain to obtain resulting shaped envelope signals. In such a way, a better signal quality can be provided without any modifications to the receiver side. And in turn, the PAPR of the envelope signal may be reduced before entering into a supply modulator and the efficiency of the ET supply modulator could be improved. As a result, the ET PA system performance can be enhanced.