In the title paper, the author proposes a Ka-Band Coplanar Magic-T Based on Gap-Waveguide (GW) Technology. The major novelty claimed in the paper is the combination of ridge-gap and E-plane groove-gap waveguides for Ka-band applications. However, such combination of these two types of waveguides in GW technology was firstly proposed in 2017. This combination allows for the realization of numerous devices, and distribution networks in the millimeter-wave band. This comment aims to properly frame the evolution of the use of RGW-GGW networks and how their use can be useful for new mm-wave band devices. While the author’s Magic-T introduces a new feature by using a 4-port network, it is clear that the concept relies on previous ideas not mentioned in the manuscript and this can lead to confusion about its actual novel contributions. In addition, we intend to give the microwave community a proper perspective of the above work’s frame of reference
