Characteristic Impedance of a Wide Slotline on Low-Permittivity Substrates (Short Paper)

Computed results on the characteristic impedance of wide slots etched on an electrically thin substrate of low dielectric constant epsilon_r are presented. These results combined with those in [1] provide design data for these slotlines. Curves are presented for epsilon_r= 2.22, 3.0, 3.8, and 9.8. Comparison is shown for the characteristic impedance between the present calculations and those available in the literature for high-epsilon_r substrates. Empirical formulas, based on least-square curve fitting, are presented for the normalized slot wavelength lambda´/lambda₀ and the characteristic impedance Z₀ over the range 0.0015<=W/lambda₀<=1.0, 0.006<=d/lambda₀<=0.06, 2.22<=epsilon_r<=9.8.