DC Limit of Microstrip Analysis Using the Spectral Domain Approach With Both Transverse and Longitudinal Currents

The spectral domain approach (SDA) is a full-wave analysis method, which is used to obtain the effective dielectric constant of the microstrip. When the operating frequency decreases to zero, by introducing the normalized transverse current, this method reduces to a generalized eigenvalue problem. In order to obtain an accurate relative dielectric constant, the normalized transverse current should be considered. The Chebyshev polynomials with edge singularity are used as the basis functions for both the normalized transverse current and the longitudinal current. The SDA at dc and the variational method can lead to the same result.