The effect of Micro Coax cable length difference on high-speed signal synchronization

In high-speed electronic systems, extremely fine coaxial cable bundles (Micro Coaxial Cable Bundle) are widely used for digital signal transmission, differential signals, and high-speed clock distribution. Due to their small diameter, high flexibility, and good shielding effect, they are very suitable for applications with tight spaces and weight sensitivity. However, when multiple extremely fine coaxial cable bundles are used together, the influence of length differences is often overlooked, but it is crucial for the synchronization of high-speed signals and system stability. This article will analyze the impact and countermeasures of length differences in detail, providing a reference for engineering design.

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The relationship between signal delay and line length

The propagation speed of a signal in a coaxial cable is determined by the dielectric constant of the material and is usually lower than the speed of light. When there is a difference in the length of the line, even if the difference is only in the millimeter range, it can cause a picosecond-level time delay, which is very sensitive in high-speed systems. For example, in a 10Gbps system, a bit period is about 100ps. If the length difference between extremely thin coaxial cables causes a 5ps delay, it is equivalent to 5% of the bit period and is sufficient to affect signal alignment and lead to data sampling errors.

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The main influence of the length difference in ultra-fine coaxial beam

1. Multi-channel synchronization issue: In parallel interfaces or multi-channel sampling scenarios, the different channels may have different arrival times due to length differences, which can lead to the system being unable to process data correctly within the same clock cycle.

Differential signal integrity degradation: When two coaxial cables form a differential pair, length differences can cause positive and negative signals to be out of sync, reducing interference resistance, and may convert to common mode noise, increasing electromagnetic interference (EMI).

Error rate increases: Timing skew causes the eye diagram at the receiving end to shrink, reducing the time margin, resulting in a significant increase in bit error rate (BER), which affects system stability.

The environmental and structural superposition effect: extremely thin coaxial cables are very sensitive to temperature, bending radius, and manufacturing tolerances. Even if the length is strictly controlled at the factory, changes in the application environment may still cause additional delay differences.

 

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How to reduce the impact of length differences

Strictly control the line length: Ensure that the lengths of multiple coaxial cables are as consistent as possible during the design phase, especially for paired differential lines.

2. Adopt the delay matching process: by selecting coaxial products that provide phase matching or delay matching, the delay error can be controlled within an extremely small range.

Reasonable wiring and fixation: Avoid excessive bending or looping of cables during system assembly, ensuring that the routing path is as symmetrical as possible.

System-level compensation: For high-demand applications, delay calibration mechanisms can be added at the circuit or chip level to further eliminate offsets caused by physical line length differences.

In high-speed signal systems, the length difference of extremely thin coaxial cable bundles directly affects signal synchronization, differential integrity, and system error rate. As the signal rate continues to increase, designers have more stringent requirements for cable length matching. Only by paying attention to cable length consistency throughout the design, manufacturing, and application processes, and taking measures such as delay matching and reasonable wiring, can the stability and reliability of high-speed systems be ensured.

I amSuzhou Huichengyuan Electronic Technology, Focus on the design and customization of high-speed signal cable harnesses and ultra-fine coaxial cable harnesses for a long time, committed to providing stable and reliable high-speed interconnection solutions. For technical consultation or more information, please contact:Manager Yin 18913280527 (WeChat number the same)。