Ten key design challenges must be overcome to optimize products for high-speed data transmission: 1. TRANSMISSION LINE The loss of the cable connection affects signal transmission. The higher the signal frequencies, the stronger the loss. As the maximum required frequency (fMAX) of a signal goes high compared to the distance that it needs to travel, simplified lumped circuit models need to be replaced with their high-frequency counterparts, such as transmission line formulation or even full wave Maxwell’s equations. The DC connectivity of metallic surfaces can no longer guarantee high- speed connectivity. 2. SIGNAL DEGRADATION Reflection and attenuation are the two main mechanisms of signal degradation. Degradation can occur at the intersection of the transmitter
and connector. If the input impedance of the transmitter is different from the input impedance of the connector, part of the input energy will reflect towards the transmitter. Some of the remaining energy will be lost in the connector due to metallic or dielectric loss, and the wave will reach the other side of the connector. While reflection is the most important mechanism of loss of signal at the connector, attenuation is the main mechanism of loss in the cable. Apart from these two effects, noise and crosstalk by other pairs can also cause problems. 3. IMPEDANCE MATCHING To optimize impedance matching (ratio of V/I or E/H), factors such as diameter of contact, distance between contacts, contact form factor, and type of materials for all components should be considered. The design of a connector can affect NEXT and FEXT performances, and the connector must also be optimized against these constraints.
Signal degradation due to attenuation and impedance mismatch: a) on the transmitter side, b) on the cable and receiver side.
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