Comments on "Coupled line 180° hybrids with lange couplers"

In the above paper, a modified coupled line 180 hybrid coupler is proposed. The modified structure introduces additional lengths in the interconnection lines between two coupled line sections for improved circuit layout flexibility. In the process, the impedance of the interconnection lines is implicitly assumed to be the same as the port impedance. This communication shows that the impedance of the interconnection lines is not limited to this single fixed value and presents more general solution for arbitrary line impedance values. The proposed solution provides much more design possibilities beyond those given in, and more design flexibility under varying design and/or manufacturing requirements. For example, some of the general solutions make it possible to design the coupler with less severe requirements on the coupling coefficients of the coupled line sections by employing interconnection lines with different impedance values from.