Comments on “Two Novel Reconfigurable PDs Based on Cascaded Transmission Lines”

In the mentioned article, Peng
et al.
proposed a three-port power divider (PD) and four-port coupler with tunable power division ratio based on: 1) cascade connection of 3-dB in-phased PD, matched tunable difference phase transmission lines (TLs), and 3-dB quadrature branch line coupler (QBLC) and 2) cascade connection of QBLC, mismatched in-phased TLs, and QBLC. However, the proposed four-port coupler provides an undesired phase difference of 90° between the output signals. Also, the scattering parameter analysis of the second design seems to be incorrect. In this letter, a correct approach is provided to analyze S-parameters.