Comments on "Near-zone gain of open-ended rectangular waveguides" [with reply]

The author comments that formulating the problem of radiation from open-ended rectangular waveguides (OEG) using an electric field integral equation (EFIE), Kawalko and Kanda (see ibid., vol.39, p.408-13, 1997) present results for the near-zone gains as a function of both the frequency and distance from the OEG aperture. These values can be considered to be exact. On the alternative methods, this paper observes that the approximate formulas need the measured values of the aperture reflection coefficient and the total radiated power. Kawalko and Kanda reply that the formula for the on-axis gain presented by Selvan (see Inst. Electron. Telecommun. Eng. J. Res., vol.43, p.61-4, 1997) certainly has an advantage over Yaghjian's formula (1984) in that it does not require knowledge of the total radiated power or the reflection coefficient at the aperture. However, this formula still does not account for all of the diffraction effects that occur at the aperture of the OEG.