Differentially-Fed Millimeter-Wave Yagi-Uda Antennas With Folded Dipole Feed

Differentially-driven Yagi-Uda antennas have been developed for millimeter-wave applications. The antennas are built on both sides of a Teflon substrate(εᵣ = 2.2). A key design aspect is the use of a folded dipole feed which increases the input impedance from 18Ω(standard dipole case) to 150Ωand is compatible with coplanar strip lines. A 7-element design results in a gain of 8–10 dB at 22–26 GHz and a cross-polarization level of< - 22~ dB. The differentially-fed Yagi-Uda antenna with folded dipole results in high radiation efficiency (> 90%at 22–26 GHz) and is suitable for mm-wave point-to-point links communication systems.