Dielectric Model
Wideband modeling of frequency dependent permittivity ensures that high speed circuit simulations maintain mathematical causality and avoid non physical signal predictions. The Svensson-Djordjevic model addresses the continuous variation of dielectric constant and loss tangent across a wide frequency range in printed circuit board laminates. This modeling approach prevents artificial signal distortions that arise when simulation tools use constant, frequency-independent substrate parameters.
Mathematical Form
Analytical expressions within this model use a continuous distribution of poles to describe the relaxation behavior of dielectric materials across a broad spectrum. By linking the real and imaginary parts of permittivity through the Kramers-Kronig relations, the Svensson-Djordjevic representation ensures causal simulation responses in the time domain. Designers input the dielectric constant and loss tangent measured at a single reference frequency, and the algorithm extrapolates these values correctly down to direct current and up to tens of gigahertz.
Simulation Value
Accurate propagation delay and dispersion calculations are achieved when simulations use this causal representation for multi gigabit transmission lines. In high speed design, the model prevents phase velocity errors that would otherwise lead to incorrect eye diagram predictions. This accuracy allows signal integrity engineers to optimize layout constraints before fabricating the first prototype.
