Segmented Digital Predistortion for High-PAPR RF Transmitters
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Solution Overview
Problem
Conventional digital predistortion techniques suffer performance degradation when used with complex modulation schemes characterized by high peak to average power ratios (PAPR) and wide signal bandwidth, especially under dynamic conditions such as LTE-TDD mode.
Innovation Solution
The implementation of segmented digital predistortion (DPD) methods, where input sample blocks are classified based on time slice and dynamic range segments, allowing for the application of different predistortion models and coefficients to improve power amplifier linearization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional digital predistortion techniques are used with complex modulation schemes, then power amplifier linearization is improved, but performance degrades under high PAPR and wide signal bandwidth conditions
Solution Approach 1:
The patent divides the input signal into multiple segments based on signal characteristics (PAPR levels, bandwidth, modulation type). Each segment is processed by a dedicated predistortion model optimized for its specific characteristics. This segmentation allows the system to maintain high linearization performance across diverse signal conditions without the performance degradation that occurs when using a single conventional DPD model for all conditions.
2Use of energy by moving object
If conventional DPD techniques are applied, then amplifier efficiency is improved by operating at less backoff, but performance suffers under dynamic conditions such as LTE-TDD mode
Solution Approach 1:
The patent implements a dynamic predistortion system that continuously monitors signal characteristics and adapts the predistortion model in real-time. The system dynamically selects and switches between different predistortion models based on current operating conditions (modulation scheme, PAPR, bandwidth, TDD timing). This dynamic adaptation maintains amplifier efficiency under dynamic conditions like LTE-TDD while preventing performance degradation that occurs with static conventional DPD approaches.
3Device complexity
If a single predistortion model is used for all signal types, then device complexity is reduced, but performance degrades with complex modulation schemes
Solution Approach 1:
The patent creates a universal predistortion framework that can handle multiple signal types and modulation schemes through a modular architecture. The system includes a library of specialized predistortion models, each optimized for specific signal characteristics. A signal characterization module automatically identifies the current signal type and selects the appropriate model from the library. This multi-functional approach achieves high linearization performance across diverse complex modulation schemes while keeping the overall device complexity manageable through systematic organization and automated model selection.
Data Source
AI summary
In an RF transmitter, a digital predistortion circuit receives a sequence of input sample blocks, and performs a digital predistortion process to produce a predistorted output signal. The digital predistortion process includes selecting a set of predistortion coefficients for an input sample block from a plurality of different sets of predistortion coefficients. Each of the plurality of different sets of predistortion coefficients is associated with a different combination of one of a plurality of time slices within a radio frame and one of a plurality of power ranges. The selected set of predistortion coefficients is associated with a time slice within which the input sample block is positioned and a power range calculated for the input sample block based on block power statistics of the sample block. The process also includes applying the selected set of predistortion coefficients to the input sample block to produce the predistorted output signal.