Asymmetric coupled-line directional coupler for application in 4 ×4 Butler matrix

A coupled-line single-section directional coupler has been design in asymmetric multilayer dielectric structure. Since in such structures capacitive and inductive coupling coefficients are not equal, a recently developed compensation technique has been used to improve the coupler´s electrical parameters. The presented approach has been verified by simulations of a 3-dB coupled-line directional coupler operating at f₀ = 24 GHz. The designed coupler has been used as a basic component of a 4 × 4 Butler matrix. The obtained performance of the Butler matrix has been verified by EM simulation of the network.