The Si9000 frequency-dependent calculations can be refined using extended substrate data. Users can assign substrate values by frequency band to accommodate material from manufacturers who specify parameters that vary by frequency. Manufacturers may specify, for example, differing values of Er across a range of frequencies, Er = 4.2 for frequencies up to 100MHz, Er = 4.15 from 100MHz up to 1GHz, Er = 4.1 from 1GHz to 10Ghz, etc.