Multi-Channel DPD Feedback for Wideband Linearization
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Solution Overview
Problem
Existing digital predistortion (DPD) systems face challenges in achieving wider bandwidth without increasing complexity and cost, particularly due to limitations in ADC sampling rates and filter requirements, leading to higher power consumption and system complexity.
Innovation Solution
Employ a DPD feedback signal with a narrow band-pass filter and utilize the filtering properties of a duplexer to reduce the bandwidth requirements, allowing for a direct learning algorithm and shared digital FIR filters, thereby reducing the need for costly ceramic filters and high sampling rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If ADC sampling rate is increased to support wider DPD bandwidth, then DPD bandwidth is improved, but power consumption and system complexity increase
Solution Approach 1:
The patent segments the wideband signal processing into multiple narrowband channels, each processed independently at lower sampling rates. This allows the overall system to achieve wideband DPD performance while each individual ADC operates at a manageable sampling rate, reducing complexity and power consumption.
Solution Approach 2:
The patent transforms the problem from a single wideband processing dimension to multiple narrowband dimensions by decomposing the wideband signal into frequency-subband components. This dimensional transformation allows parallel processing of multiple narrowband signals at lower rates rather than one wideband signal at high rate.
2Speed
If ADC sampling rate is increased to support wider DPD bandwidth, then DPD bandwidth is improved, but power consumption increases
Solution Approach 1:
The patent segments the wideband signal processing into multiple narrowband channels, each processed independently at lower sampling rates. This allows the overall system to achieve wideband DPD performance while each individual ADC operates at a manageable sampling rate, reducing complexity and power consumption.
Solution Approach 2:
The patent applies partial action by processing only the necessary frequency subbands at full resolution while other subbands use reduced resolution processing. This selective approach reduces overall power consumption while maintaining adequate DPD performance across the complete bandwidth.
3Reliability
If ceramic filters are used to reduce spectral regrowth, then linearity is improved, but cost and device complexity increase
Solution Approach 1:
The patent replaces the mechanical ceramic filter system with a digital signal processing-based DPD system. Instead of using physical filters to reduce spectral regrowth, the invention uses digital predistortion algorithms that compute and apply correction signals, eliminating the need for costly and complex ceramic filters while achieving comparable or superior linearity performance.
4Reliability
If digital predistortion is applied to compensate for nonlinearities, then linearity is improved, but computational complexity increases
Solution Approach 1:
The patent segments the DPD computation into multiple narrowband processing channels, each with its own simplified predistortion model. This segmentation reduces the computational complexity of each individual processing path while maintaining overall linearity performance across the complete wideband signal through the combination of all narrowband processed channels.
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.