Differentially Fed Directional Couplers With Coupled-Conductors of Unequal Widths

In this letter, coupled-line directional couplers with differentially excited balanced coupled lines are considered in which balanced lines having different widths are proposed. Different conductor widths allow for coupling control within a chosen dielectric stack-up and give design freedom in terms of coupling adjustment. The theoretical analysis is confirmed by experimental verification, in which a broadband asymmetrical 3-dB two-section directional coupler has been designed and measured.