Page 9 - Power & Data Connectivity Expand Electronic Capabilities eBook
P. 9

Low skew
Electricity flows through a wire at a finite speed, defined as the propagation velocity of the signal. If a signal is flowing at the same speed through different wire lengths, the signal will not take the same time to pass through each wire. This results in skew. The wires’ insulation materials also impact the propagation velocity. If a cable is designed with wires made with different insulating materials, a skew can appear regardless of the different lengths of wire. The skew is a key parameter because high speed networking technologies use several wires/pairs in the cable. If the skew is significant between each wire/pair, signals sent at the same time from one end of the cable may arrive at a different time to the receiver. In this case, the receiver does not correctly interpret the original signal. Several solutions exist to minimize skew in a cable:
• Use two coaxial cables
• Use parallel pair (with no twist, skew is limited)
• Change the configuration and the geometry of the cable
• • • • • • • • •
» Comparison of two eye patterns (same media, same data rate): good skew on the left hand side, bad skew on the right hand side
Low crosstalk between ways
Crosstalk occurs in any system with two or more conductors. Each wire segment acts individually as an inductor and a capacitor. Consequently, a signal transmitted through one circuit or transmission line creates an undesired effect in another circuit or transmission line. Crosstalk must be reduced to guarantee good signal integrity.
    Non-optimized connector
Optimized connector
» Crosstalk measurements for optimized Axon’ MicroMach connector and a non-optimized connector. The lower the crosstalk, the better the link.
» Axon’ male MicroMach made with four differential contact pairs

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