Modeling of Unshielded Suspended and Inverted Substrate Microstrip Lines

Microstrip transmission lines have an important rule in designing microwave integrated circuits. In this paper, we will illustrate modeling of unshielded microstrip lines using finite element method (FEM). We specifically determine the capacitance per unit length, inductance per unit length, and characteristic impedance of unshielded suspended and inverted substrate microstrip lines. We compare our results with those obtained by other methods and found them to be in agreement.