Contactless Air-Filled Substrate Integrated Cavity-Backed Slot Antenna Array With Improved Printed Ridge Gap Waveguide Feeding Network

A contactless air-filled substrate integrated cavity-backed slot antenna array is designed utilizing gap waveguide (GW) technology in this article. To enhance realized aperture efficiency, a contactless air-filled substrate integrated waveguide (CLAF-SIW) is implemented to construct a TE210-mode resonance cavity for feeding 2
$\times $
2 slot elements. Moreover, an improved printed ridge GW (I-PRGW) is proposed for the first time to achieve the feeding network for feeding each air-filled resonator cavity uniformly with the same amplitude and phase. In order to mitigate the sensitivity of the antenna to the relative position between the coupling slot and the feed transmission line, the shielded stripline is integrated on the same dielectric layer as the coupling slot. Furthermore, the shielded stripline serves as the transition from the I-PRGW to the grounded coplanar waveguide (GCPW) for measurement. A physical prototype of the antenna array, comprising 4
$\times $
4 slot elements, is manufactured. The experimental results demonstrate that the proposed antenna array, incorporating the transition structure, exhibits a wide impedance andwidth ranging from 28.3 to 40 GHz with a reflection coefficient better than −10 dB, corresponding to a fractional bandwidth of 34.3%. The maximum realized boresight gain is measured to be 20.02 dBi at 38 GHz while achieving a maximum realized aperture efficiency of 67.8%.