A monolithically printed filtering waveguide aperture antenna

This letter presents the design of a 3 ^rd order filtering waveguide aperture antenna based on coupled cavity resonators. Three offset-coupled rectangular waveguide cavities are employed in the design realizing two nested loaded-stubs without costing extra structure and size. The loaded-stubs introduce two controllable transmission zeroes and enhance the out-of-band realized gain selectivity. To validate the predicted results, a prototype operating at the X- band frequencies has been fabricated monolithically using the 3-D selective laser melting printing technique. The measured results are in very good agreement with the simulated results, showing a flat gain response of 7.0 ± 0.2 dBi from 9.5–10.5 GHz with very good out-of-band selectivity. The fractional bandwidth is about 10% at 10 GHz when S ₁₁ = -20 dB. Compared to the previously designed filtering antennas, the proposed design has the advantages of stronger out-of-band gain selectivity and low profile.