Single-PCB Fabricated, Ultrawideband, and Wide-Scanning Phased Array Antenna With Vertically Integrated Resistive Frequency-Selective Surface

A novel ultrawideband phased array antenna that vertically integrates a resistive frequency-selective surface (FSS) is proposed to achieve a bandwidth ratio of 15:1. This antenna operates from 0.8 to 12 GHz and is designed to be fabricated on a single printed circuit board (PCB). The active voltage standing wave ratio (VSWR) for the infinite array is lower than 3.2 at broadside. It remains lower than 2.9, 3.3, and 4.3 when scanning to 60° in E-plane, D-plane, and H-plane, respectively. At first, the tightly coupled dipole with the vertically integrated resistive FSS (RFSS) and the overlapping pad is designed to mitigate the short-circuited effect and cancel the reactance of the nearby ground plane, respectively. Then, the shorted posts are added to mitigate the non-radiating common mode, which also introduces the radiating loop mode into the proposed antenna. However, the central resonant frequency of the loop mode is far from the operating frequency bands. To address this issue, the cavity-backed overlapping pad is designed to change the loop path. By adjusting the position of the shorted posts, the central resonant frequency of this loop mode is moved to around 2 GHz. Moreover, to lower the active VSWR when scanning and then improve the radiation efficiency, the wide-scanning impedance matching FSS and the double-layer RFSS with the modified structures are employed. Finally, a
$17\times17$
array prototype is built and measured to verify these designs.