Comments on “Branch-Line Couplers Using Unequal Line Lengths”

In the above paper
[1]
, Toker
et al.
proposed a general solution of branch-line coupler which is a perfect design. Since this paper was published, it has been widely cited by and referenced in the other papers and patents. However, when we referred to it, we found a wrong equation. The expression in
[1, eq. (4)]
is as follows:
\begin{equation} A^{o}=D^{o}=\cos \theta _{1} +\frac {Z_{1} \sin \theta _{1}}{Z_{2} \sin \frac {\theta _{2}}{2}}. \end{equation}