DAC LUT Compensation for Dynamic Distortion in High-Speed Transmitters
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Solution Overview
Problem
High-speed transmitters face dynamic distortion, which is influenced by both precursor and postcursor symbols, and existing compensation methods are inadequate, leading to signal degradation and increased power consumption.
Innovation Solution
A digital compensation technique using a lookup table (LUT) and shift registers to adjust input values for a digital-to-analog converter (DAC), combined with methods like equalization and amplitude scaling, to address dynamic distortion by iteratively updating LUT values until desired signal characteristics are met.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional compensation methods are used, then device complexity is reduced, but dynamic distortion compensation effectiveness deteriorates
Solution Approach 1:
The patent segments the dynamic distortion compensation into multiple independent LUTs, where each LUT handles a specific precursor or postcursor symbol. This segmentation allows the system to address dynamic distortion from multiple symbols simultaneously without requiring a single complex compensation device, thus improving compensation effectiveness while maintaining manageable device complexity.
Solution Approach 2:
The patent transitions from traditional time-domain equalization to a multi-dimensional approach by incorporating both temporal dimension (precursor and postcursor symbols) and amplitude dimension (multiple LUTs for different amplitude levels). This dimensional expansion enables comprehensive dynamic distortion compensation that accounts for interactions between multiple symbols at different amplitude levels.
2Productivity
If high-speed transmission is implemented, then data transfer rate is improved, but dynamic distortion increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing compensation values in LUTs before actual data transmission. The LUTs are populated with compensation values that account for dynamic distortion effects of precursor and postcursor symbols, allowing the system to compensate for high-speed transmission distortion without real-time complex calculations, thus maintaining high data transfer rates while reducing dynamic distortion.
3Reliability
If multiple LUTs are used for comprehensive distortion compensation, then distortion compensation effectiveness is improved, but device complexity increases
Solution Approach 1:
The patent applies local quality by assigning specific LUTs to handle specific aspects of dynamic distortion - separate LUTs for precursor symbols, postcursor symbols, and different amplitude levels. Each LUT is optimized for its specific function rather than using a single general-purpose LUT, improving overall compensation effectiveness while keeping each individual LUT relatively simple.
4Measurement precision
If iterative LUT updating is performed, then compensation accuracy is improved, but power consumption increases
Solution Approach 1:
The patent implements periodic action by performing iterative LUT updating only during calibration phases rather than continuously during data transmission. The LUTs are updated periodically to adapt to changing conditions, achieving high compensation accuracy while minimizing power consumption by avoiding continuous real-time updates during high-speed data transmission.
Data Source
AI summary
A device and method of operation for digital compensation of dynamic distortion. The transmitter device includes at least a digital-to-analog converter (DAC) connected to a lookup table (LUT), a first shift register, and a second shift register. The method includes iteratively adjusting the input values via the LUT to induce changes in the DAC output that compensate for dynamic distortion, which depends on precursors, current cursors, and postcursors. More specifically, the method includes producing and capturing average output values for each possible sequence of three symbols using the shift register and LUT configuration. Then, the LUT is updated with estimated values to induce desired output values that are adjusted to eliminate clipping. These steps are performed iteratively until one or more check conditions are satisfied. This method can also be combined with techniques such as equalization, eye modulation, and amplitude scaling to introduce desirable output signal characteristics.