Narrowband DPD Feedback Path for Wideband Multi-Channel Transmitters
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Solution Overview
Problem
Existing digital predistortion (DPD) systems face challenges in increasing bandwidth without significantly increasing complexity and cost, particularly in multi-channel wideband wireless transmitters, due to limitations in ADC sampling rates and filter requirements, which lead to higher power consumption and system complexity.
Innovation Solution
The implementation of a DPD feedback signal with a narrow band-pass filter in the feedback path, allowing for reduced bandwidth requirements in digital and analog components, and the use of direct learning algorithms to minimize the need for complex digital FIR filters and multi-pole ceramic filters, thereby extending DPD bandwidth without costly modifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the instantaneous bandwidth for DPD is increased to meet next generation wireless system requirements, then the processing speed and bandwidth capability are improved, but the system complexity, cost, and power consumption increase significantly
Solution Approach 1:
The patent segments the wideband signal processing into multiple narrowband parallel channels. Each channel is processed independently at lower sampling rates, avoiding the need for a single high-speed wideband processor. This segmentation allows the system to achieve wideband coverage through parallel narrowband processing, reducing the complexity and power consumption of individual processing units while maintaining overall wideband capability.
2Speed
If the sampling rate for DPD is increased to handle wider bandwidth, then the bandwidth coverage is improved, but the power consumption and system cost increase
Solution Approach 1:
The patent divides the wideband signal into multiple narrowband frequency segments that are processed in parallel. Each segment is processed at a lower sampling rate appropriate for its bandwidth, rather than processing the entire wideband signal at a high sampling rate. This segmentation approach reduces the power consumption of ADCs, digital signal processors, and other components while maintaining the overall wideband processing capability through parallel operation.
3Speed
If complex digital FIR filters are used to handle wideband signals, then the bandwidth处理能力 is improved, but the device complexity and cost increase
Solution Approach 1:
The patent replaces complex wideband FIR filters with multiple simpler narrowband filters operating in parallel. Each narrowband filter processes a specific frequency segment with reduced complexity requirements. This segmentation approach maintains the overall bandwidth processing capability while significantly reducing the complexity and computational load of individual filter structures.
Solution Approach 2:
The patent introduces frequency segmentation as an intermediary step between the input wideband signal and the filtering stage. By first dividing the wideband signal into narrowband segments through frequency domain decomposition or filtering, the system enables the use of simpler filters that operate on reduced bandwidth signals, thereby reducing overall system complexity while maintaining wideband processing capability.
4Reliability
If multi-pole ceramic filters are used to reduce spectral regrowth over wide frequency bands, then the linearity is improved, but the device complexity and cost increase
Solution Approach 1:
The patent segments the frequency band requiring linearization into multiple narrower sub-bands. Instead of using complex multi-pole ceramic filters to cover the entire wide frequency range, the system employs simpler filters for each sub-band processed in parallel. This segmentation approach achieves the required linearity and spectral regrowth control while reducing the complexity and cost of individual filter components.
Data Source
AI summary
A method of operating a communications system includes receiving a signal at a digital predistorter (DPD), introducing predistortion to the signal using the DPD, and converting the predistorted signal to an analog signal using a digital-to-analog converter having a first bandwidth. The method also includes amplifying the analog signal, sampling the amplified signal using an analog-to-digital converter having a second bandwidth less than the first bandwidth, and extracting coefficients of the DPD from the sampled signal.