Millimeter-Wave Gain-Enhanced Yagi–Uda Antenna Array With Third-Order-Mode Driven Dipole and Short Reflector

A millimeter-wave Yagi–Uda antenna comprising a third-order-mode driven dipole and a short reflector is proposed for gain enhancement. First, new design considerations for the director or reflector are proposed because of the reverse current along the third-order-mode driven dipole. Four schemes of the parasitic elements are analyzed when the driven dipole operates in the third-order mode. Then, a three-element Yagi antenna driven by the third-order-mode driven dipole with a short reflector as an example is designed. The measurement shows a maximum gain of 8.1 dBi over a −10 dB impedance bandwidth from 25.2 to 27.4 GHz (8.6%). After that, an array is formed using the proposed antenna. The investigation shows that compared with conventional basic-mode driven Yagi–Uda antenna arrays, the proposed third-order-mode driven Yagi–Uda antenna arrays achieve similar gains with a 40% reduction of the number of array elements. A two-element array operating at the third-order mode in the millimeter-waveband is fabricated and measured. The array gets a peak gain of 11.2 dBi, with measured
$|\text {S}_{11} | < -10$
dB from 25.0 to 27.2 GHz (8.5%).