Baseline Wander Correction Loop With Adaptive Amplitude Estimation
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Solution Overview
Problem
Conventional methods for correcting baseline wander in communication systems, such as those used in SDI video applications, suffer from inaccuracies due to rail out and non-idealities, leading to increased bit errors, and feedforward circuits are ineffective in accurately canceling baseline wander.
Innovation Solution
A baseline wander correction scheme utilizing an equalization adaptation engine, specifically an SS-LMS equalization adaptation engine, is employed to estimate signal amplitude only when pathological data patterns are not detected, combined with a high-gain dual-feedback loop and amplitude estimation loop to correct baseline wander, ensuring accurate amplitude estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a quantized feedback loop with analog amplitude estimation is used to correct baseline wander, then baseline wander correction is achieved, but rail out occurs in the presence of offset due to positive feedback leading to increased bit errors
Solution Approach 1:
The patent employs a feedback loop that continuously monitors the output signal and adjusts the baseline wander correction accordingly. The feedback mechanism compares the actual output with the desired output and modifies the correction signal to prevent rail out while maintaining accurate amplitude estimation, thereby reducing bit errors without causing saturation.
Solution Approach 2:
The patent introduces an intermediary signal processing stage between the baseline wander correction and the output amplifier. This intermediary circuit acts as a buffer that prevents direct coupling of the correction signal from causing rail out, while still allowing effective baseline wander cancellation through controlled signal injection.
2Measurement precision
If energy detection filters and rectifiers are used for amplitude estimation, then amplitude estimation is achieved, but inaccuracies occur due to offsets, data patterns, and other non-idealities
Solution Approach 1:
The patent extracts the amplitude estimation function from the conventional energy detection path and implements it separately using a dedicated estimation loop. This separation allows the estimation circuit to operate independently from the main data path, preventing offsets and data patterns from corrupting the amplitude measurement while maintaining continuous monitoring capability.
Solution Approach 2:
The patent changes the operating parameters of the amplitude estimation circuit by using a controlled feedback mechanism that adjusts the estimation bandwidth and gain based on detected signal conditions. This dynamic parameter adjustment allows the system to maintain accurate amplitude estimation across varying data patterns and offset conditions by adapting the estimation process to current signal characteristics.
3Object-affected harmful factors
If a feedforward circuit is used to replace quantized feedback, then rail out is prevented, but accurate baseline wander cancellation cannot be achieved
Solution Approach 1:
The patent merges the advantages of both feedback and feedforward approaches by combining a feedforward baseline wander correction path with a feedback amplitude estimation loop. The feedforward path provides immediate correction without risk of rail out, while the feedback loop continuously refines the correction accuracy by monitoring output conditions and adjusting the estimation parameters accordingly.
Data Source
AI summary
Systems, circuitry and methods correct baseline wander while reducing amplitude difference between the input signal to a data sampler and the output signal of an output-swing-controlled buffer. Example baseline wander correction circuitry comprises a baseline wander correction loop that receives an equalized data signal, a feedback signal and a buffer control signal, and corrects baseline wander in the data sampler input signal. Baseline wander correction loop generates the buffer output signal based on the data sampler output signal and the buffer control signal. Baseline wander correction circuitry also comprises a feedback circuit that receives the data sampler output signal and generates the feedback signal, and an amplitude estimation loop that receives the data sampler input and output signals and outputs the buffer control signal to control the peak-to-peak swing of the buffer output signal.