Where does the crosstalk in extremely thin coaxial cable bundles come from? Key factors engineers must focus on

As electronic systems continue to move towards high-speed and miniaturization, extremely thin coaxial cable bundles (micro coaxial cable) are widely deployed in camera modules, vehicle electronics, VR/AR devices, chip testing systems, and server internal interconnections, among other applications. Although it has advantages such as compact size, high bandwidth, and strong shielding performance, in actual engineering, crosstalk remains one of the design challenges that cannot be ignored.

What is crosstalk?
Crosstalk refers to the electromagnetic field from a high-speed switching signal line, which couples to adjacent conductors, causing interference signals that should not appear to be mixed into other channels. In extremely thin coaxial bundles, due to the small wire diameter, high density, and fast transmission speed, such interference is more likely to appear. Common impacts include:
1.1 Signal jitter increases, eye diagram opening decreases
1.2 Noise and spikes occur at the receiver, even error signals
1.3 System error rate increases, the reliability of the data link decreases

The main reasons for crosstalk formation
2.1 Limited line spacing: Micro cables are often highly integrated. When multiple cables are arranged in parallel, the risk of electromagnetic coupling increases.
2.2 Impedance discontinuity: In connector, solder joint, and transition board areas, impedance changes will bring parasitic effects, making the coupling problem more significant.
2.3 Inadequate return path: If multiple signal lines share a ground return path, it is easy to form common-mode coupling, leading to an increase in crosstalk level.
2.4 High signal frequency and steep edges: The faster the rise and fall edges, the richer the spectral components, and the stronger the interference on adjacent bundles.

Three, common strategies for reducing crosstalk
3.1 Material selection and shielding optimization: Use high-quality micro coaxial cables and add multi-layer shielding structures as required to enhance isolation capabilities.
3.2 Adjust wiring structure: Minimize long-distance parallel wiring, appropriately increase line spacing, or use interleaved arrangement to reduce coupling.
3.3 Optimize grounding system: Provide relatively independent stable return paths for each high-speed line to avoid common-mode interference caused by shared ground lines.
3.4 Impedance Continuity Control: Ensure smooth transition in the interface area and adopt reasonable termination methods to suppress high-frequency reflections and interference components.
3.5 Enhance Simulation and Testing: Assess the coupling trend in advance through simulation tools, and then verify and adjust by indicators such as eye diagram and bit error rate.

Extremely fine coaxial cable bundles, with their high density and high-performance characteristics, are widely used in various high-speed interconnection scenarios. However, if crosstalk issues are not properly controlled in the design, they will directly affect the stability of the system. Comprehensive optimization in the aspects of cable, layout, electrical structure, and test verification is necessary to ensure that their performance is fully utilized.
I am[Suzhou Huichengyuan Electronic], Year-round specializing in the customization and R&D of high-speed signal cable harnesses and ultra-thin coaxial cable harnesses, proficient in providing reliable and highly consistent interconnection solutions for various applications. For further consultation, please feel free to contactManager Yin 18913280527 (WeChat same number)。