Half-Mode Cavity-Based Planar Filtering Antenna With Controllable Transmission Zeroes

A two-pole half-mode substrate integrated waveguide (HMSIW) cavity-based filtering antenna is presented. The HMSIW cavity is used as a radiating resonator with a conventional substrate integrated waveguide (SIW) cavity functioning as a high- $Q$ resonator of the filter, leading to its compact size. The concept of source-load coupling is introduced for filtering antennas, which allows for the presence of two controllable transmission zeroes (TZs) in the frequency response of proposed design. This is accomplished by using electric coupling between two resonator cavities and a combination of microstrip/coaxial line to feed the antenna. The single-layer printed circuit board structure provides a broadside gain of 4.3 dBi at the operating frequency of 5.5 GHz. Gain curves are plotted at the broadside of the antenna, clearly showing a quasi-elliptic response and a 3-dB bandwidth of 2.6%.