Multi-Band DPD Pipelines for Shared Power Amplifier Chains
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Solution Overview
Problem
Conventional systems for digital predistortion in multi-band communications require separate transmit chains for each band, leading to high component count and power consumption, making it impractical to reuse circuitry across bands due to the wide bandwidth needed for DPD correction.
Innovation Solution
The implementation of a transmit processor with multiple DPD pipelines that include cross-modulation and inter-modulation DPD circuits, mix-and-sum circuits, and an adaptive DPD engine, which allows for shared circuitry across bands by calculating and compensating for cross-modulation and inter-modulation distortions, reducing the need for separate signal chains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate transmit chains are used for each band, then DPD correction can be performed for each band independently, but the number of components and power consumption increase significantly
Solution Approach 1:
The patent merges multiple transmit chains into a single shared transmit chain that handles multiple bands simultaneously. The key innovation is the multi-band DPD circuit that can process and correct nonlinearities for multiple bands through one shared HPA, eliminating the need for separate HPAs and DPD circuits for each band while maintaining correction accuracy through sophisticated digital signal processing
Solution Approach 2:
The shared HPA and DPD circuit are designed to be universal, capable of handling multiple frequency bands (e.g., Band A, Band B, Band C) through software-configurable parameters. The DPD circuit can be dynamically reconfigured via lookup tables and coefficient adjustments to provide optimal correction for different band combinations without requiring hardware changes
2Device complexity
If circuitry is reused across multiple bands, then power consumption and component count are reduced, but DPD correction becomes infeasible due to prohibitively wide bandwidth requirements
Solution Approach 1:
The patent segments the DPD correction process into band-specific processing stages. Each band's signal is processed independently through its own DPD pipeline (with baseband processing, cross-modulation correction, and inter-modulation correction), and the corrected signals are then combined. This allows the system to handle wide aggregate bandwidth while maintaining manageable correction rates for each individual band
Solution Approach 2:
The patent introduces a new dimension of processing by implementing cross-modulation correction that operates between different bands. The DPD circuit not only corrects inter-modulation within each band but also compensates for cross-modulation effects between bands, enabling accurate correction across the wide aggregate bandwidth through multi-dimensional signal processing
3Device complexity
If a single DPD circuit handles wide bandwidth for combined bands, then circuitry reuse is achieved, but the feedback ADC must operate at prohibitively high sampling rates requiring significant digital support hardware
Solution Approach 1:
The patent segments the feedback processing into band-specific pipelines, where each pipeline processes feedback for a specific band at its appropriate sampling rate. The feedback ADC can operate at lower rates corresponding to individual band requirements rather than the aggregate wide bandwidth, and the segmented processing preserves the ability to correct nonlinearities for each band independently
Solution Approach 2:
The system dynamically adjusts processing parameters including sampling rates, filter coefficients, and lookup table configurations based on which bands are currently active. This allows the feedback ADC to operate at optimized lower sampling rates when only subset of bands are in use, while still providing comprehensive correction when all bands are active through coordinated multi-pipeline processing
Data Source
AI summary
Traditionally, for multi-band communication systems, independent signal chains for each of the different bands are employed. By using such an architecture, there are a large number of components, and there is substantial power consumption. Here, transmit processor is provided that enables transmission across multiple bands using few components (namely, fewer signal chains), while also provided for digital predistortion.