Phase Delay Skew

Timing Variation

Differences in the propagation time between two or more signals on a circuit board can lead to errors in high-speed data recovery. Excessive phase delay skew occurs when the physical path lengths or the local dielectric environments of a signal pair are not identical. This mismatch causes the signals to arrive at the receiver at different times, which can close the data eye or cause timing violations.

Engineers must manage these differences in multi-gigabit interfaces like DDR memory or PCIe lanes.

Propagation Velocity

Speed of a signal is determined by the effective dielectric constant of the material surrounding the conductor. If one trace passes over a glass bundle while another passes over a resin-rich area, they will travel at different velocities. This phenomenon is known as the glass-weave effect and is a major source of timing variation in modern electronics.

Even if the traces are the exact same length, the difference in material properties can create several picoseconds of delay. Using spread glass or routing at an angle to the weave helps to average out these effects and minimize the resulting timing errors.

System Failure

Bit errors increase when the clock signal is no longer aligned with the data window. If the timing difference exceeds the margin of the receiver, the entire link may fail to initialize or maintain a stable connection.

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