Vertically Polarized Broadband Gain Stable Yagi– Uda Antenna for Millimeter-Wave Applications

A millimeter-wave endfire Yagi–Uda antenna based on a monopole fed by a substrate-integrated waveguide (SIW) line is presented in this letter. The antenna consists of two substrates assembled perpendicularly in a 3-D configuration. The vertical plane supports the driven monopole antenna and a group of passive parasitic monopoles, all printed as conductor strips. The horizontal layer contains the SIW feeding line, where the top metallic face acts as a mirror for the monopoles. According to the beam direction and the achieved gain, a parametric study is conducted to determine the number of elements. Two versions are proposed, studied, and experimentally validated. The first version with one arm achieved a $-$ 10 dB impedance bandwidth of 23.5% (27.4–34.7 GHz) with a peak gain of 13.8 dBi. The second version with three arms of directors is proposed to achieve a stable gain of 15.1 $\pm$ 0.5 dBi over 16% (27.1–32 GHz). The performance of the proposed antenna with relatively compact size makes it suitable for millimeter-wave systems.