Air-filled cavity-backed 28 GHz Antenna array implemented by 2.5D PCB process and Network Analysis

A 28 GHz air-filled cavity-backed microstrip antenna array, which is embedded in a polyphenyl ethers (PPE)-based multilayer printed circuit board (PCB), is presented. The air cavity is implemented by a novel 2.5D PCB process with a no-flow prepreg, to improve radiation efficiency, bandwidth, and directivity while maintaining a low profile. A four-element antenna array was designed, simulated, and measured. The measurement results yield a bandwidth of 3.8% centered at 28.5 GHz and a realized gain of 14.8 dBi with the antenna substrate thickness of
$0.035\lambda_{0}$
and the separation of
$0.8\lambda_{0}$
between elements. Network analysis for a single patch section of the designed antenna with transmission line (TL) models is discussed as well. The comparison between the analyzed, simulated, and measured input impedance shows a good agreement over the given frequency band.