ISI Cancellation Circuit for Data and Zero-Crossing Sampling
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Solution Overview
Problem
Conventional CDR circuits fail to systematically address inter symbol interference (ISI) at zero crossings, leading to uncontrolled ISI effects that compromise bit error ratios and eye margin stability, necessitating a method to minimize ISI at both data and zero crossing points simultaneously.
Innovation Solution
An apparatus comprising an ISI cancellation circuit and a detector circuit configured to minimize ISI at data and zero crossing sampling points within a symbol interval, using shared or sequential architectures to generate data and crossing samples, thereby balancing vertical and horizontal eye margin optimization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional DFE equalization is used to minimize ISI at data samples, then vertical eye margin is maximized, but ISI at zero crossings remains uncontrolled
Solution Approach 1:
The patent divides the ISI cancellation function into two separate cancellation circuits: one dedicated to data sampling points and another dedicated to zero-crossing sampling points. This segmentation allows each circuit to independently optimize for its specific sampling point type, resolving the contradiction between vertical and horizontal eye margin maximization.
Solution Approach 2:
The patent applies local quality by designing different cancellation circuits with tailored feedback waveforms suited to specific locations in the signal. The data ISI cancellation circuit uses feedback waveforms optimized for data sampling points, while the crossing ISI cancellation circuit uses feedback waveforms optimized for zero-crossing points, ensuring each location receives appropriate ISI compensation.
2Manufacturing precision
If feedback waveform magnitude is optimized for data samples, then data ISI is minimized, but feedback magnitude at zero crossings becomes uncontrolled
Solution Approach 1:
The feedback control function is segmented into two independent circuits: the data ISI cancellation circuit controls feedback magnitude for data samples, while the crossing ISI cancellation circuit controls feedback magnitude for zero crossings. This segmentation provides systematic control over feedback at each location without increasing overall system complexity.
Solution Approach 2:
The patent implements feedback mechanisms in both cancellation circuits, where the detected symbols are fed back through appropriately shaped waveforms to cancel ISI. The feedback is systematically controlled at both data sampling points and zero-crossing points, ensuring predictable and reliable ISI cancellation at both locations.
Data Source
AI summary
An apparatus comprising an inter symbol interference (ISI) cancellation circuit and a detector circuit. The inter symbol interference (ISI) cancellation circuit may be configured to minimize ISI at data sampling and crossing sampling points in a symbol interval of an input signal. The detector circuit may be configured to generate data samples and crossing samples at the data sampling and crossing sampling points in the symbol interval of the input signal.