The real invisible killer of high-speed signals: not the chip, but the harness

Today, with the widespread use of high-speed interfaces, engineers increasingly encounter problems such as signal jitter, bit errors, and unstable links. Many people intuitively suspect chip, motherboard design, or protocol settings, but the root cause of the failure of high-speed links is often hidden in the most unobtrusive part—the cable assembly. Especially in the era of high-speed signals with frequencies as high as GHz, old-style cable assemblies are no longer capable of handling high-integrity transmission tasks.

---

Why Have Old Wiring Harnesses Become the Hidden Weakness of High-Speed Systems?

Traditional wiring harnesses had very simple requirements in the low-speed era, just needing to "conduct electricity." Therefore, the wire diameter was thick, the structure was loose, the shielding was rudimentary, and impedance was uncontrollable, none of which affected 40-50 MHz signals. However, when the system is upgraded to several Gbps or even higher-speed links, any impedance突变, shielding缺失, or poor crimping can cause reflections, crosstalk, and eye diagram collapse. An old wiring harness that has been in use for many years may become a fatal weakness for the entire high-speed link.

---

Why ultra-fine coaxial cable becomes the best solution for high-speed signals

To achieve high bandwidth transmission in compact spaces, ultra-thin coaxial cables (Micro Coax) have emerged. They consist of multiple layers including a central conductor, insulation layer, metallic shielding, and outer sheath, which can provide stable characteristic impedance and excellent anti-interference capability within an extremely small diameter. Today, camera modules, AI mainboards, autonomous driving systems, MIPI, and USB4 devices almost all regard micro coax as a standard. However, many devices only replace the module but not the cable harness during upgrades. The new module is designed at the GHz level, while the old cable harness still adheres to the MHz standard, resulting in significant loss of high-speed signals during transmission, leading to a substantial decrease in performance.

---

The real problem is not the chip, but the weakest link in the link.

When a high-speed link is abnormal, it is most likely to be misdiagnosed as insufficient chip performance or a motherboard design flaw. However, in engineering practice, a large number of issues originate from cable aging, connector reflections, impedance discontinuities, or improper shielding. If the cable itself limits the bandwidth, even the most advanced chip is of no help. Worse still, the grounding and shielding layout of old-style cables is chaotic, which can even cause crosstalk, further deteriorating the overall link quality. Therefore, when troubleshooting high-speed issues, the cable is often the most critical part to check first.

---

As high-speed systems develop towards higher frequencies, the requirements for cable performance become more stringent. An old-style cable can be the biggest obstacle to the stability of a high-speed link. Therefore, engineers must consider cable upgrade as a key step when performing system upgrades or new platform verification, and prioritize the use of micro coax or high-shielding structures to ensure impedance continuity, effective shielding, and proper connectors. In the world of high-speed signals, details determine success or failure, and cables are the most easily overlooked detail that requires the most attention.

I am[Suzhou Huichengyuan Electronic Technology]Long-term focused on the design and customization of high-speed signal cables and ultra-fine coaxial cables, committed to providing stable and reliable high-speed interconnection solutions. If you have related needs or want to learn more, please contact Manager Zhang:18913228573 (WeChat number)。