In the field of high-speed interconnects, the USB interface is undergoing a rapid evolution from USB 3.0 to USB 4. With data transfer rates crossing over from 5Gbps, 10Gbps to 20Gbps, 40Gbps, and even higher, the electrical performance and structural design of cable systems have become particularly crucial. To achieve stable high-speed transmission within limited spaces, extremely thin coaxial cables (micro coaxial cable) have gradually become the mainstream solution for USB high-speed interconnect design. Its advantages in impedance control, shielding capability, high bandwidth, and flexible cabling provide a reliable guarantee for high-performance USB systems.
Part 1: Structure and Characteristics of Ultra-Fine Coaxial Beam
A super-thin coaxial cable assembly is a miniature coaxial cable structure designed for high-speed signal transmission, consisting of a central conductor, insulating medium, outer shielding layer, and protective sheath. The multicore bundle is used for high-speed internal interconnection within equipment. Compared with traditional twisted pair cables or FFC flexible flat cables, it has significant advantages:
Excellent impedance consistency, reducing signal reflection and echo loss
Excellent high-frequency performance, low insertion loss, low latency, supporting signal transmission of tens of Gbps
3. Strong anti-interference ability, complete shielding layer effectively resists external EMI, and simultaneously suppresses inter-channel crosstalk
High flexibility and small size, suitable for internal wiring of compact equipment
These characteristics make ultra-fine coaxial cables widely used in high-speed interfaces such as USB4, MIPI, HDMI, and PCIe.
The core challenges of USB3~USB4 transmission
USB4 achieving stable transmission of 40Gbps requires balancing signal integrity and electromagnetic compatibility, with main challenges including:
Impedance mismatch leads to signal reflection and eye diagram closure, increasing the bit error rate.
High-frequency attenuation becomes more obvious as the cable length increases and the frequency becomes higher.
Interference and EMI interference, the impact of signal interference between channels in high-speed multi-channel transmission affect stability
4. Mechanical and thermal stress, long-term bending or temperature changes of compact internal wiring may lead to failure of connection points.
Controlling impedance, loss, and shielding performance is a key factor in the design of USB4 high-speed cables.
Advantages of High-Speed Transmission of Ultra-Fine Coaxial Beam
Extremely fine coaxial bundles have many advantages in high-speed transmission:
Precision impedance control, ensuring the signal and ground distribution are concentric, reducing reflections and jitter
Low loss and high bandwidth, using silver-plated conductors and low dielectric constant materials, maintaining good performance above 16GHz
High shielding against interference, outer metal braiding or foil layer provides 360° shielding, reducing external interference and crosstalk between channels
Flexible wiring and reliable connections, adaptable for wiring in confined spaces, and can be paired with miniature connectors to achieve high-density modular connections
Through reasonable design and selection, high-speed USB3~USB4 signals can be realized with low error rate and high stability in extremely thin coaxial cable bundles.
As USB interfaces move towards higher bandwidths, ultra-thin coaxial cable bundles, with their excellent electrical properties and structural flexibility, have become the key carriers for stable transmission of USB3 to USB4. It solves issues such as high-speed signal attenuation, interference, and impedance matching, while also meeting the requirements of miniaturization and high integration within devices. In the future, ultra-thin coaxial cable bundle design and process optimization will still determine the performance ceiling of high-speed interconnect systems in USB4, Thunderbolt, DisplayPort, and other high-speed interfaces.
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Suzhou Huichengyuan Electronic Technology, Long-term focus on the design and customization of high-speed signal cable harnesses and ultra-fine coaxial cable harnesses, committed to providing stable and reliable high-speed interconnection solutions. For more information, please feel free to contact
Yin Manager: 18913280527 (same WeChat number)。
