Analysis of circular waveguides with soft and hard surfaces realized by strip‐loaded walls using asymptotic boundary conditions

Soft and hard walls are realized for a circular waveguide with walls coated by a uniform dielectric layer of appropriate thickness and loaded with conducting strips. The strips are oriented along the waveguide axis (z‐axis) for hard surfaces or φ‐directed for soft surfaces in a periodic form. The simple approximate asymptotic strip boundary condition (ASBC) is used to analyze the structure. For the dominant mode, when the waveguide walls are hard or soft, a linear field distribution across the waveguide cross section can be obtained. Then the waveguide can be used as an antenna with good linear polarization. The characteristics of such waveguides are presented with sample radiation patterns as compared with hollow waveguide radiation patterns.