Clock Distribution via Common Trace for Phase Alignment
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Solution Overview
Problem
Communication equipment, such as network elements, face challenges in achieving precise phase alignment of clock signals across line cards due to varying trace sizes and environmental conditions like temperature variations, which existing static propagation delay compensation techniques struggle to address.
Innovation Solution
A method and system where a timing device distributes clock signals and request pulses using the same trace to estimate propagation delays, allowing line cards to adjust their phase delay offsets, thereby reducing errors from trace length asymmetry and environmental variations, without interrupting normal clock signal distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple traces are used to distribute clock signals to different line cards, then each line card can receive clock signals independently, but the varying trace sizes cause different propagation delays that make phase alignment difficult
Solution Approach 1:
The patent combines the clock signal distribution function and the propagation delay measurement function into a single trace. The trace serves dual purposes: distributing the clock signal to the line card and carrying the test signal for measuring propagation delay. This eliminates the need for separate measurement traces and simplifies the overall trace configuration while enabling accurate phase alignment compensation.
Solution Approach 2:
The trace is designed to perform multiple functions simultaneously: it acts as both a clock signal distribution channel and a measurement channel for propagation delay characterization. By making the trace universal, the patent reduces the total number of traces needed and simplifies the backplane configuration while maintaining the ability to achieve precise phase alignment across different line cards.
2Adaptability or versatility
If static propagation delay compensation is used, then initial phase alignment can be achieved, but environmental variations like temperature changes cause drift in propagation delays that static compensation cannot address
Solution Approach 1:
The patent implements periodic measurement of propagation delay by continuously or regularly sending test signals through the trace to characterize changes in propagation delay caused by environmental variations. This periodic characterization enables the system to adapt to temperature changes and other environmental factors that affect signal propagation, maintaining accurate phase alignment over time and across varying conditions.
3Productivity
If separate traces are used for clock signal distribution and test signal transmission, then measurement can be performed without interrupting clock distribution, but the number of traces required increases
Solution Approach 1:
The patent merges the clock signal distribution trace and the test signal trace into a single shared trace. The test signal is transmitted through the same trace used for clock distribution, eliminating the need for separate measurement traces. This reduction in trace quantity simplifies the backplane design and reduces manufacturing complexity while maintaining the ability to perform propagation delay measurements.
Solution Approach 2:
The patent uses periodic test signal transmission through the shared trace to measure propagation delay without requiring dedicated continuous measurement traces. By inserting test signals periodically into the existing clock distribution trace, the system achieves measurement functionality using the same physical infrastructure, thereby reducing the total number of traces needed while maintaining measurement capability.
Data Source
AI summary
Methods and system for clock alignment are described. In an example, a timing device can distribute a clock signal to a line card via a trace of a backplane. The timing device can further send a pulse to the line card at a first time via the trace. The timing device can further receive a return pulse from the line card at a second time via the trace. The timing device can determine a time difference between the first time and the second time. The time difference can indicate a propagation delay associated with the line card and the trace. The timing device can send the time difference to the line card. The line card can adjust a phase delay offset of the line card using the time difference.