Signal Loss
High speed signal transmission through internal circuit board layers experiences a reduction in amplitude as the signal propagates along a trace. This power reduction is called stripline attenuation, and it is governed by both the electrical properties of the surrounding dielectric and the resistance of the copper conductor itself. Unlike microstrip traces that run on the outer layers, a stripline trace is embedded between two continuous ground planes, which increases the capacitance and influences the loss characteristics.
Designers must model this reduction to ensure that signals arrive at the receiver with sufficient voltage margin.
Material Impact
Dielectric absorption is a major contributor to high-frequency losses as the frequency of operation rises into the gigahertz range. Choosing a low-loss resin system can minimize the dielectric contribution to the stripline attenuation, though this often increases material costs. Roughness of the copper foil on the trace boundaries also increases conduction losses due to the skin effect at high frequencies.
Geometric Influence
Trace width and copper thickness are important layout parameters that affect the electrical resistance of the transmission line. A wider trace reduces the conduction loss and decreases the overall stripline attenuation, though it requires more space and changes the trace impedance unless the dielectric thickness is adjusted. Balancing these geometry choices is a critical step in multi-layer board design.
