Signal Displacement
High speed signaling pairs suffer when the timing of the true and complementary waves fails to arrive at the receiver simultaneously. This differential phase distortion arises from physical inconsistencies in the dielectric environment surrounding the two copper traces. It converts some of the differential energy into common mode noise, which radiates out from the board.
High frequency designs require precise symmetry to minimize the introduction of jitter. Every mismatch in local capacitance contributes to the total error at the end of the line.
Fiber Influence
Woven reinforcements inside the circuit board create a grid of high and low permittivity regions. If one trace of a pair runs over a bundle of glass while the other sits over resin, differential phase distortion becomes inevitable because the signals travel at different speeds. This variation exists regardless of how accurately the trace lengths are matched.
Designing around this requires using spread fabrics or rotating the layout. Inconsistency in the weave creates unpredictable shifts in signal arrival times.
Receiver Acceptance
Signal integrity depends on the eye diagram remaining open enough for the receiver logic to distinguish between bits. If differential phase distortion is excessive, the crossover point of the wave shifts until the signal becomes unintelligible. This loss of margin reduces the link reliability.
Proper board fabrication controls the dielectric consistency to keep these shifts within the margins defined by the hardware protocol. Performance remains stable when the substrate is homogeneous.
