SIW Cavity-Fed Filtennas for 5G Millimeter-Wave Applications

In this article, novel millimeter-wave (mmWave) filtennas (filtering antennas) are proposed to realize compact size and low insertion loss for 5G applications. It is achieved by employing eighth-mode substrate-integrated waveguide (EMSIW) cavities fully shielded by metallized vias and cover as resonators, which are named as fully shielded EMSIW (FSD-EMSIW) cavities. Interdigital coupling between cavities is introduced in order to obtain higher coupling strength for wideband operation. The proposed single-polarized antenna consists of a feeding stripline, two FSD-EMSIW cavities, and two stacked square patches, generating the four-order filtering antenna response. Furthermore, this design has been extended to realize a dual-polarized filtenna by employing double sets of feeding network. For demonstration, single-/dual-polarized filtenna prototypes were fabricated and measured, the measured results show that the 5G mmWave band (24.25-29.5 GHz) can be covered with average gains of 4.5 dBi. Good bandpass filtering response is also observed. Finally, to validate the proposed idea in array applications, a 16-element filtenna array is designed and measured with good performance.