Tuning Skew Measurement Using Programmable Clock Source
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Solution Overview
Problem
Current skew measurement methods using time-domain reflectometers (TDR) with standardized testing signals fail to accurately assess cable specifications, leading to erroneous conclusions about cable compliance with industry standards, especially in modern computing systems where data signals operate in MHz/GHz bands, resulting in unnecessary cable scrapping.
Innovation Solution
A programmable clock source is configured to generate a modified clock signal that matches the frequency profile of the target computing system, allowing for more accurate skew measurement by driving testing signals onto conductors that better represent the actual signals used in the system, thereby improving the accuracy of cable performance assessment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a standardized testing signal is used for skew measurement, then the testing process is simple and consistent, but the measurement accuracy does not reflect actual system performance
Solution Approach 1:
The patent implements a programmable clock source that can dynamically adjust its frequency response characteristics to match different target systems. Instead of using a fixed standardized testing signal, the apparatus can be configured with different frequency responses (e.g., 125 MHz, 250 MHz, 500 MHz, 1 GHz) depending on the specific application requirements. This dynamic adaptability allows the testing apparatus to achieve accurate skew measurements for various systems while maintaining a relatively simple base architecture through software-controlled configuration.
Solution Approach 2:
The patent changes the frequency response parameters of the testing signal to match the target system's operating characteristics. By adjusting parameters such as clock frequency, rise time, and spectral content, the testing apparatus can accurately measure skew for different applications (e.g., SATA, SAS, PCIe) without requiring fundamentally different hardware. This parameter-based approach resolves the contradiction by enabling high measurement precision through configurable parameters rather than complex hardware modifications.
2Reliability
If a standardized testing signal with fixed frequency response is used, then the testing apparatus is easier to operate, but it leads to erroneous conclusions about cable compliance
Solution Approach 1:
The programmable clock source allows the testing apparatus to adapt its frequency response dynamically based on the target system being tested. Pre-configured frequency response profiles for different standards (SATA, SAS, PCIe, etc.) enable reliable compliance assessment by matching actual operating conditions. The system maintains ease of operation through automated selection or simple user selection of the appropriate profile, eliminating the need for complex manual adjustments while ensuring reliable results.
Solution Approach 2:
The patent creates accurate copies of the target system's actual signal characteristics using the programmable clock source. By replicating the frequency response, rise time, and spectral content of real data signals, the testing apparatus can assess cable compliance under conditions that closely mirror actual system operation. This copying approach ensures reliable compliance assessment while maintaining operational simplicity through pre-defined signal templates.
3Measurement precision
If the testing signal frequency content does not match the target system requirements, then the testing process is faster and simpler, but the skew measurement is inaccurate
Solution Approach 1:
The programmable clock source enables the testing apparatus to quickly switch between different frequency response configurations matched to specific target systems. Pre-configured profiles for various standards allow the system to adapt to different testing requirements without manual reconfiguration, maintaining high testing efficiency. The dynamic reconfigurability ensures that each test uses the appropriate frequency content for accurate skew measurement while preserving productivity through automated configuration management.
Solution Approach 2:
The patent changes the frequency response parameters of the testing signal to match the target system's operating characteristics. By adjusting parameters such as clock frequency, rise time, and spectral content based on the specific application, the system achieves accurate skew measurements for different standards. This parameter-based approach maintains testing efficiency by allowing rapid reconfiguration through software control rather than requiring physical hardware changes or time-consuming manual adjustments.
Data Source
AI summary
Embodiments herein discuss tuning a testing apparatus to better match the input response of a target system in which a cable will be used. For example, conductors in the cable may have a different skew depending on the system in which they are used. The testing apparatus may be tuned using frequency information regarding the type of signals that will be driven on the cable when installed in the target system. In one embodiment, the testing apparatus uses the frequency information to configure a programmable clock source that can be used to shape a reference clock and control a driver to match the signals in the target system. Using the clock source to modify the reference clock results in the driver outputting a testing signal that better reflects the actual signals that will be transmitted on the cable in the target system.