Comments on "Aperture Coupling Between Microstrip and Resonant Cavities" [Letters]

In the above paper, the authors have considered the case of coupling between two identical microstrips in Section II-B. The equivalent model of parallel plate waveguide with magnetic side walls (Fig. 3) has been used for the determination of normalized reactance of a small aperture. The notations and relations of [1] have been used directly for analyzing this equivalent model. It may be noted, however, that the case considered in [1] is of transmission through a transverse plane while the case considered by the authors of the above paper is transmission through broad wall of the guide Fig. 2(b). Therefore, the end result obtained in Section II-B is not convincing.