A Miniaturized Vivaldi Antenna in Fan-out Wafer-Level Package for 5G Millimeter Wave Applications

In this letter, a miniaturized Vivaldi antenna based on fan-out wafer-level packaging (FOWLP) process with a single redistribution layer (RDL) is proposed. A step-by-step design procedure for the proposed antenna is presented. By introducing the slots and semicircular-shaped loads, its low-end cut-off frequency is extended from 35.28 to 24.04 GHz, leading to a size reduction by 31.8% when normalized to the lowest operating frequency. Moreover, a wideband low-pass coplanar waveguide to slotline transition is proposed for antenna feeding, in which a folded split ring resonator and etching periodic slots are added to reduce the transition insertion loss above 40 GHz. Prototypes of the proposed antenna and back-to-back coplanar waveguide to slotline transition were fabricated and measured. The measured return loss of the BTB transition is better than 13.4 dB from DC to 67+ GHz, and the insertion loss of a single transition is below 0.95 dB. The measured |S11| of the proposed antenna is less than -10 dB from 23 to 67+ GHz with 4.5-7.1 dBi measured gain and >84% simulated efficiency.