Empirical Relations for Capacitive and Inductive Coupling Coefficients of Coupled Microstrip Lines

Empirical relations for inductive and capacitive coupling coefficients are proposed. The functional relationships are based on the physical mechanism of coupling in microstrip lines. Values of coupling coefficients computed from even- and odd-mode impedances and phase velocities, available in the literature, are compared with those computed from the proposed relations. Microstrip couplers have been designed on the basis of coupling coefficients to meet the desired coupling and isolation.