Remote Unit DPD Timing Alignment for PA Linearity Control
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Solution Overview
Problem
Remote units in wireless communications systems face challenges in satisfying regulatory and operational requirements due to unwanted distortion terms like third-order intermodulation distortion (IMD3), which affect adjacent channel power ratio (ACPR) and power amplifier efficiency and linearity.
Innovation Solution
Incorporating a digital predistortion (DPD) circuit with a DPD front-end circuit that generates a digital training signal with a predefined waveform pattern to accurately determine timing offset, allowing the DPD circuit to add an artificial distortion term that cancels unwanted distortion terms in the RF signal, thereby improving power amplifier efficiency and linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If digital predistortion circuit is used to cancel unwanted distortion terms, then power amplifier linearity and regulatory requirements compliance are improved, but device complexity increases
Solution Approach 1:
A DPD front-end circuit is introduced as an intermediary component between the digital signal source and the DPD circuit. This front-end circuit generates training signals with predefined waveform patterns and provides timing alignment, enabling the DPD circuit to accurately determine timing offsets and effectively cancel distortion terms without requiring complex processing in the main remote unit architecture.
Solution Approach 2:
The DPD front-end circuit performs preliminary actions by generating training signals with known waveform patterns before the main DPD processing occurs. This preliminary timing alignment and signal preparation enables the DPD circuit to accurately determine timing offsets and create effective predistortion, simplifying the overall system complexity while maintaining compliance with regulatory requirements.
2Measurement precision
If training signal with predefined waveform pattern is used for timing alignment, then timing offset determination accuracy is improved, but device complexity increases
Solution Approach 1:
The DPD front-end circuit changes the signal parameter by generating training signals with predefined waveform patterns (such as specific frequency sequences or time-domain patterns). These known patterns enable the DPD circuit to accurately determine timing offsets through correlation or matching operations, achieving high measurement precision without requiring complex synchronization protocols.
Data Source
AI summary
Digital predistortion (DPD) timing alignment in a remote unit(s) for a wireless communications system (WCS) is disclosed. In examples discussed herein, a remote unit includes a power amplifier (PA) configured to amplify a radio frequency (RF) signal before transmission. The RF signal may include an unwanted distortion term and a DPD circuit is provided in the remote unit to create an artificial distortion term to help cancel out the unwanted distortion term. The remote unit includes a DPD front-end circuit configured to generate a digital training signal corresponding to a predefined waveform pattern. The DPD circuit can be configured to perform a DPD timing alignment based on the predefined waveform pattern to determine a timing offset that is need to create the artificial distortion term. As such, it may be possible to effectively cancel the unwanted distortion term in the RF signal to improve efficiency and linearity of the PA.