Comments on “Quasi-Arbitrary Phase-Difference Hybrid Coupler”

A novel hybrid coupler with nonstandard phase difference has been reported recently by Wong in 2012, which shows promising potentials in applications like the feeding networks for phased array antenna. However, it is found that the design equations of Wong are incomplete because of the neglect of an interrelated constrain between the design parameters (Z₂ and θ₂) and a constant relationship between the parameters (Z₂ and Z₃). This letter rectifies the design formulas for this phase-difference hybrid coupler and demonstrates that the analytical solution for electrical parameters can be uniquely obtained to a certain phase-difference value. The bandwidths of the different phase variations for general phase-difference coupler are presented. In addition, the analysis for the arbitrary coupling level and arbitrary phase-difference hybrid coupler is proposed and closed-form design equations are given.