This paper presents a new gain-enhancement technique for a compact dipole-Yagi antenna operating at 28 GHz for millimeter-wave 5G applications. Unlike conventional Yagi–Uda antennas, in which director elements are arranged only along a single plane in front of the driven element, the proposed design employs symmetrically paired directors placed on both the top and bottom layers of the antenna structure. Moreover, these director pairs are deliberately positioned away from the conventional central front region of the dipole, resulting in enhanced electromagnetic field confinement and stronger end-fire radiation. Comprehensive parametric studies and full-wave electromagnetic analyses demonstrate a notable gain improvement compared to traditional single-layer Yagi antennas of similar size, while maintaining a compact form factor. Based on the proposed gain-enhancement concept, a four-element end-fire array antenna is designed, fabricated, and experimentally validated. The measured reflection coefficients, radiation patterns, and realized gain show good agreement with simulation results, confirming stable impedance matching and high directional performance across the 28 GHz band. Furthermore, the multiple-input multiple-output (MIMO) performance of the four-element array is evaluated for smartphone applications indicates satisfactory performance of the designed array antenna for cellular user equipment. Owing to its high gain, compact size, and favorable MIMO behavior, the proposed antenna represents a promising solution for next-generation 28 GHz 5G user equipment.
Basherlou et al. (Mon,) studied this question.