Design of Bi-Level-Microstrip Quadrature Directional Couplers with Indirectly Coupled Lines

In the paper the design of coupled-line directional couplers is presented in which the lines are not directly coupled. Instead an additional conductor is utilized to provide the coupling between the two transmission lines. The proposed realization technique is easily applicable in practical designs and the design procedure does not require advanced analysis of multi-conductor coupled lines, instead a simple calculator for single microstrip line is required.