Receiver Clock Phase Tuning for Maximum Vertical Eye Opening
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Solution Overview
Problem
Conventional digital data receivers face challenges in accurately sampling high-speed serial data streams without a clock signal, as channel effects can distort the eye diagram, leading to suboptimal sampling points that do not maximize the vertical eye opening, resulting in increased bit error rates.
Innovation Solution
A method and apparatus that generate a clock signal and iteratively adjust its phase to maximize the vertical eye opening of the signal, using a phase shifter and controller to determine the optimal sampling time, even in asymmetrical eye diagrams, thereby improving signal-to-noise ratio and reducing bit error rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the midpoint of the bit period is used for sampling as determined by conventional clock recovery, then the sampling process is simple and straightforward, but the sampling point may not maximize the vertical eye opening when channel effects distort the eye diagram, resulting in increased bit error rates
Solution Approach 1:
The patent implements feedback by measuring the vertical eye opening at the sampling point and using this measurement to adjust the sampling phase. The eye opening measurement feeds back to the phase adjustment mechanism, creating a closed-loop system that continuously optimizes the sampling point to maximize eye opening and minimize bit error rate.
Solution Approach 2:
The patent transforms the static sampling point (fixed at midpoint) into a dynamic sampling point that can be adjusted based on eye opening measurements. The sampling phase becomes variable, allowing the system to adapt to channel conditions and find the optimal sampling point that maximizes vertical eye opening.
2Adaptability or versatility
If the sampling phase is fixed at the midpoint determined by clock recovery, then the receiver operation is simple, but it cannot adapt to asymmetrical eye diagrams caused by channel effects, leading to suboptimal signal-to-noise ratio
Solution Approach 1:
The receiver performs self-adjustment by automatically measuring its own eye opening and using this measurement to correct its sampling phase. The system serves itself by generating the correction signal internally from its own performance metric (eye opening measurement), eliminating the need for external calibration or complex adaptive algorithms.
Solution Approach 2:
The patent replaces complex adaptive signal processing mechanisms with a simpler measurement-and-adjustment approach. Instead of using sophisticated equalization or adaptive filtering algorithms, the system uses direct eye opening measurement to drive phase adjustment, substituting mechanical/simple measurement feedback for complex computational methods.
3Reliability
If iterative phase adjustment is performed to maximize vertical eye opening, then bit error rate is reduced and signal quality is improved, but the processing time and computational complexity increase
Solution Approach 1:
The patent performs preliminary eye opening measurements during an initialization or training phase before normal data reception. By conducting the iterative phase adjustment and convergence process beforehand, the system establishes the optimal sampling point in advance, allowing subsequent data reception to use the pre-determined phase without requiring continuous iterative adjustment during critical data transmission.
Data Source
AI summary
A clock generator generates a clock signal used for sampling a received signal by a comparator which compares the received signal to a reference. A phase shifter adjusts the phase of the first clock signal and a controller adjusts the phase of the clock signal to maximize the vertical eye opening of the signal at the sampling time. In an example embodiment, the phase of the clock signal is adjusted in a first direction and a measure of vertical eye opening of the signal is compared to a previous measure. If the measure of vertical eye opening has increased the signal another phase adjustment is made in the same direction and if the vertical eye opening of the signal has decreased a further phase adjustment in the opposite direction is made. By increasing the vertical eye opening of the signal the signal-to-noise ratio of the received signal is improved.