An analysis of the matching and directional characteristics of waveguide and horn radiators

Using computer analysis and experimental investigation, it is shown that the solution to Lewin's problem of radiation from an open-ended rectangular waveguide with an infinite perfectly conducting flange adequately describes the radiation and reflection of electromagnetic waves from an open-ended rectangular waveguide without a flange. Lewin's theory is extended to oversized multimode waveguides and to the case where a waveguide filled with a dielectric with an arbitrary permittivity radiates into a medium with a different permittivity. The normalized complex admittances, magnitude and phase of the reflection coefficient, and radiation patterns of waveguide and horn radiators are calculated.