Dielectric loaded circular waveguide feeds

In this paper, dielectric loaded circular waveguide feeds are designed and investigated for radiation pattern equalization. The small diameter circular waveguide feed has unequal radiation patterns in the principal planes, which are not suitable for prime focus reflectors. To make the pattern equalization, the dielectric rod is used inside the waveguide. It further reduces the overall diameter of the waveguide. The antenna is designed at 10 GHz, with dielectric constant ε_r = 2.5 and loss tangent 0.002. The numerical result shows that the radiation patterns are symmetrical in the principal planes with 10-dB beamwidths of 126°, cross-polarization level is -27.6 dB, and back lobe level is -31.4 dB, when the dielectric rod is extended by a 0.5 λ₀ from the aperture with a rod radius a = 0.3 λ₀. The S₁₁ of the antenna is also investigated and it is below -10 dB within the frequency band of 8 to 12 GHz.