A simple evaluation of losses in thin microstrips

A simple modification of Wheeler´s incremental inductance rule is presented which allows the extention of the use of this rule for the evaluation in quasi-TEM operation of losses in thin microstrips (i.e., when the Wheeler´s rule is considered no longer applicable). A good agreement of the proposed formula with available numerical results is obtained when thickness is comparable with skin depth. A comparison is also made with two approximate formulas proposed by some authors. The proposed modification to Wheeler´s rule should be useful for computer-aided design (CAD) of monolithic microwave integrated circuits (MMIC´s)