Thunderbolt high-speed transmission's invisible hero: extremely thin coaxial cables

In the era of rapidly evolving high-speed interconnect technology, the Thunderbolt (雷电) interface is hailed as the "all-in-one interface" among high-performance devices thanks to its multifunctional features of compatibility with data, video, and power supply. However, the real key technology behind supporting data rates of up to 40 Gbps and even higher is not the interface itself, but the extremely fine coaxial cable (Micro Coaxial Cable) used internally. It determines whether the Thunderbolt cable can maintain stable and high-fidelity signal transmission in complex environments.

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Why high-speed interfaces need to shift from traditional cables to ultra-fine coaxial cables

With the evolution of interfaces such as USB, HDMI, and others towards higher speeds, traditional twisted pair or ribbon cables are difficult to meet the integrity requirements of tens of Gbps-level signals. As the speed increases, impedance fluctuations, crosstalk, insertion loss, and EMI can all lead to signal distortion and communication failure. Thunderbolt 3/4/5's differential high-speed signals are extremely sensitive to the transmission medium, so it is necessary to use extremely thin coaxial cables with symmetrical structure, perfect shielding, and controllable impedance to ensure clear eye diagrams and stable delay during high-speed transmission.

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The structural advantages and transmission characteristics of ultra-fine coaxial lines

Extremely thin coaxial cables can be understood as miniature versions of RF structures, consisting of multiple layers including a central conductor, insulating layer, metal shielding, and sheath. Their key advantages include:

Strong shielding capability: Multi-layer metal shielding effectively inhibits external interference and signal leakage.

Impedance consistency: Strict geometric structure control allows it to easily maintain 50 Ω or 100 Ω standard impedance.

Extremely low skew deviation: The natural symmetrical structure makes the skew of the differential signal extremely small, ensuring timing consistency.

Small in volume and high in flexibility: Can flexibly route even in compact structures such as laptops and tablets.

A lightning cable usually contains dozens of parallel independent coaxial cores, each bearing the stable transmission task of a high-speed data channel.

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The core reason why Thunderbolt must use a very thin coaxial cable

Meet the ultra-high-speed signal integrity requirements:

Thunderbolt's dozens of Gbps speed requires extremely low insertion loss, excellent impedance control, and minimum crosstalk. The coaxial structure has a natural advantage in these indicators.

Support multi-functional mixed transmission:

The lightning cable carries data, video, and power supply, with multiple signals transmitted in parallel in a compact space, which must rely on coaxial independent shielding to ensure they do not interfere with each other.

Follow the trend of slim and light devices

Extremely thin wire diameter and flexibility make it the best choice for internal wiring in notebooks, tablets, and other devices.

Future-oriented applications for higher bandwidth:
Thunderbolt 5's signal frequency has entered the tens of GHz range, and only Micro Coax can support future higher-speed, lower-loss interconnect standards such as USB4, PCIe extension, VR, and so on.

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The ultra-fine coaxial cable is the core foundation for the high-speed and stable communication of Thunderbolt 3/4/5. From signal integrity, anti-interference ability, mechanical flexibility to future scalability, Micro Coax provides indispensable support for high-speed interfaces. As data rates continue to increase and device structures become increasingly compact, such cables will continue to play a key role in more high-performance interconnection fields.

I amSuzhou Huichengyuan Electronic Technology Co., Ltd., long-term focused on the design and customization of high-speed cable harnesses and ultra-thin coaxial cable harnesses, committed to providing customers with stable and reliable high-speed interconnection solutions. If you have related needs or want to learn more, welcome to contact Manager Zhang :18913228573 (WeChat number)。