SerDes Baseline Wander Compensation Before ADC Sampling
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Solution Overview
Problem
High bit error rates in gigabit rate links due to baseline wandering caused by AC coupling components, which introduce frequency variations and distortions in analog signals, complicating data integrity and requiring inefficient ADCs with wide dynamic ranges.
Innovation Solution
A transceiver system that compensates for baseline wandering in the analog stage by using an AC coupler, analog to digital converter, digital equalizer, slicer, subtraction block, digital to analog converter, low pass filter, and signal summation circuit to remove baseline wandering before digital conversion, thereby reducing power consumption and thermal noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If AC coupling components are used in gigabit rate links, then data transmission is enabled, but baseline wandering causes frequency variations and distortions that increase bit error rates
Solution Approach 1:
The patent applies preliminary action by compensating for baseline wandering in the analog stage before the ADC converts the signal to digital. The system uses a feedback loop with a slicer, DAC, and low-pass filter to generate a baseline wandering estimate that is subtracted from the analog signal prior to ADC conversion. This preliminary compensation prevents baseline wandering from degrading signal quality before digital processing, thereby maintaining data integrity at gigabit transmission rates
2Reliability
If ADCs with wide dynamic ranges are used to compensate for baseline wandering, then data integrity is maintained, but power consumption increases
Solution Approach 1:
By performing baseline wandering compensation in the analog domain before ADC conversion, the patent reduces the dynamic range requirement for the ADC. The feedback loop generates an estimate of baseline wandering that is subtracted from the analog signal, thereby removing the low-frequency wander component that would otherwise require the ADC to handle with extended dynamic range. This preliminary removal of baseline wandering allows the use of lower-power ADCs while maintaining data integrity
Solution Approach 2:
The patent replaces the traditional approach of using high dynamic range ADCs (digital domain compensation) with an analog domain compensation approach using a feedback loop. Instead of relying on the ADC to handle baseline wandering through wide dynamic range, the system substitutes a continuous-time feedback mechanism that actively removes baseline wandering before conversion, thereby reducing power consumption
3Reliability
If baseline wandering is removed in the digital stage, then data integrity is improved, but thermal noise and power consumption increase
Solution Approach 1:
The patent removes baseline wandering in the analog stage before ADC conversion rather than in the digital stage. This preliminary removal in the analog domain prevents baseline wandering from being converted to digital noise, thereby avoiding the generation of additional thermal noise that would occur with digital stage compensation. The feedback loop continuously estimates and removes baseline wandering, preventing it from degrading the signal before digital conversion
Data Source
AI summary
A transceiver system compensates for baseline wandering in an analog signal in the analog stage before sampling the analog signal and processing the analog signal in the digital stage. The transceiver system includes an analog to digital converter that samples the analog signal after baseline wandering compensation, a digital equalizer to condition the digital samples, and the slicer to determine transmitted symbols from the digital samples. The transceiver system includes a subtraction block that determines the difference between an input and an output of the slicer, a digital to analog converter that converts a difference between the input and the output of the slicer, a low pass filter that filters out high frequency components of the difference between the input and the output of the slicer thereby to extract out the baseline wandering, and a signal summation circuit that subtracts the baseline wandering from the analog signal.