Multilayer Planar Transmission Lines

This chapter discusses the single‐layer reduction (SLR) formulation applicable to the multilayer planar transmission lines. It presents the basic formulation of the SLR applied to the multilayer microstrip lines to compute dispersion, dispersive characteristic impedance, dielectric loss, and conductor loss. The concept of the effective relative permittivity converts the inhomogeneous medium microstrip to an equivalent isotropic homogenous medium microstrip line. The SLR process is also applicable to reduce the multilayer lossy symmetrically coupled microstrip lines to an equivalent single‐layer substrate. Two separate equivalent substrates, the even‐mode equivalent substrate and the odd‐mode substrate, could be obtained to compute the dispersion, frequency‐dependent characteristic impedance, dielectric and conductor losses of both the even and odd modes. The chapter also presents the basic formulation of the SLR applied to the multilayer asymmetric coplanar waveguide (CPW)/CPW structures to compute dispersion, dispersive characteristic impedance, dielectric loss, and conductor loss.