In today's advanced electronic products such as drones, laptops, wearable devices, and medical electronics, ultra-fine coaxial cables (Micro Coaxial Cable) have become an important component for high-speed signal transmission. Known for their small size, high flexibility, and excellent electrical performance, they are widely used in systems with tight spaces and dense signals. However, many engineers often overlook a crucial detail during design or use—the impedance mismatch. This seemingly minor deviation can directly affect signal quality and system stability.
What is impedance matching?
In short, impedance matching is to keep the impedance of the signal source, transmission line, and load consistent. When the three impedances are equal, the signal can be transmitted smoothly without reflection, thus maintaining the integrity of the waveform and the stability of the system.
For extremely thin coaxial cables, the common design impedance is 50Ω or 75Ω, depending on the application scenario. Once it deviates from this range, issues such as signal attenuation, waveform distortion, and crosstalk interference may occur.
Two, the five major impacts of impedance mismatch
Signal reflection and waveform distortion
When the impedance is not matched, part of the signal energy will be reflected back, superimposed on the original signal to form waveform distortion. This not only leads to signal distortion but may also cause data errors, affecting the stability of system communication.
Signal attenuation and reduced transmission distance
Impedance differences can cause increased signal energy loss, and signal strength decays rapidly with distance. This phenomenon is particularly evident in high-speed transmission applications, which can directly shorten the effective communication distance.
Crosstalk increases, interference intensifies
In high-density cable arrangement, impedance mismatch will amplify electromagnetic interference (EMI) between adjacent cables, causing crosstalk problems, which in turn affects the normal signal transmission of other channels.
4. EMC testing is difficult to pass
Imbalance in impedance leads to the deterioration of the overall electromagnetic compatibility (EMC), making the equipment more prone to exceed EMI test standards. This not only increases the cost of rectification but may also delay the product launch cycle.
5. High-speed signal integrity damaged
In high-speed interfaces such as MIPI, LVDS, USB 3.0, and HDMI, impedance mismatch significantly affects the opening degree of the **eye diagram**, leading to increased bit error rate, which in turn affects image quality and transmission speed.
How to avoid impedance mismatch?
1. Choose high-precision manufactured Micro Coaxial Cable
High-quality wire can ensure that the impedance is controlled within ±5% range, ensuring transmission consistency from the source.
Optimize PCB and connector impedance design
Reasonably plan the wiring width, routing layer, and connection method to achieve system-level impedance matching.
Use professional testing equipment
By using instruments such as TDR (Time Domain Reflectometer) to detect cable impedance consistency, deviations can be identified and corrected in a timely manner.
Pay attention to the bending radius of the wire harness.
Over bending or sharp bending can cause impedance change, affecting signal integrity, and the minimum bending radius specifications should be followed.
Although the volume of extremely fine coaxial cables is small, their role in high-speed signal systems is crucial. Impedance matching not only relates to signal quality but also affects the overall EMC performance and data integrity of the system. Therefore, strict control of impedance matching should be maintained in all aspects of selection, layout, processing, and testing to ensure stable, efficient, and reliable transmission of the cable束.
I am Kunshan JieKangFu Precision Electronics. We have been focusing on the design and customization of high-speed signal cables and ultra-thin coaxial cables for a long time, committed to providing stable and reliable high-speed interconnection solutions to our customers. If you have any related needs or would like to learn more, please feel free to contact us:
Manager Yin 18913280527 (WeChat number the same)。
