Bandwidth Enhancement of Aperture Feed by an Air Rectangular Cavity Backing in a LTCC Post-Wall Waveguide

Abstract

The aperture feed with an air cavity in a LTCC (Low Temperature Co-fired Ceramics) post-wall waveguide with dielectric constant ε_r more than 5 is proposed for bandwidth enhancement in the millimeter wave band. A rectangular cavity is adopted because only one mask pattern of a rectangular can be used for each layer of LTCC for reducing the number of the design parameters and the cost. The fabrication limitation such as the spacing between the post edge and the aperture edge reduces the bandwidth. The feeding structures are designed at 61.25GHz for a range of ε_r from 2.0 to 9.0. In the case of ε_r =7.0, the bandwidth for reflection below -15 dB with the air cavity is 4.25 times that without the air cavity in simulation, and 3.10 times in measurement.