A Millimeter-Wave End-Fire Antenna Array

This paper presents a millimeter-wave end-fire antenna array design with improved compactness and broad-band performance. The proposed architecture introduces a pair of horizontally symmetric two-terminal open-circuit U-shaped dipoles as an alternative to conventional folded dipoles. A half-wavelength resonator excitation is implemented to overcome the characteristic high input impedance of folded dipoles, resulting in dual reflection zeros that enable broadband operation. The miniaturized planar antenna element array measures 0.43λ<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> × 0.25λ<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf>. Experimental measurements of a fabricated 1 × 4 array with directors demonstrate excellent performance characteristics, including 10 dB impedance matching over a frequency range of 24-34 GHz and a consistent average gain of 10.1 dBi.