Accurate approximations for a function appearing in the analysis of microstrip

A simple, accurate, closed-form approximation is given for the function Q(x), which appears in formulas for several properties of microstrip transmission lines. The approximation is then used to obtain simple expressions for certain line parameters associated with microstrip structures. The study is motivated by the consideration that if Q could be approximated in closed form using only elementary functions, the expressions for line capacitance, inductance, and edge admittance for microstrip would become quite simple. These expressions would then be more attractive for design work on small calculators.