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 (??r = 2.2). A key design aspect is the use of a folded dipole feed which increases the input impedance from 18 ?? (standard dipole case) to 150 ?? and 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.