Comments on “Coupling Coefficient Reconfigurable Wideband Branch-Line Coupler Topology With Harmonic Suppression”.

In the above paper two equivalent circuits of $L_{T}-$ and $\Pi $ -types for a 90° transmission-line section (TL) are suggested only for $N = 1$. However, the design formulas for $N= n$ , where $n\ge 1$ and integer, are already published for $L_{T}$ -types and for $\Pi $ -types [3, Fig. 6(c) with $\Theta _{a}= 0^{\circ }$ ], , and the advantages for $N \ge 2$ are verified for $L_{T}$ -types in and $\Pi $ -types , , as well. [ABSTRACT FROM AUTHOR]