Millimeter-Wave Wideband Endfire Magnetoelectric Dipole Antenna Fed by Substrate Integrated Coaxial Line

Abstract

A wideband endfire magnetoelectric (ME) dipole antenna fed by substrate integrated coaxial line (SICL) is presented. Endfire radiation is achieved by the combination of a horizontally oriented quarter-wave shorted patch and a dipole array loaded at the patch aperture. A direct-feeding mechanism based on the SICL structure is developed to excite the ME-dipole antenna. The proposed feeding method provides a simple yet effective mean of wideband impedance tuning. The antenna exhibits a wide impedance bandwidth of 77%, covering from 23.1 to 52 GHz, and a small lateral size of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.32\lambda _{0}$ </tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{0}$ </tex-math></inline-formula> refers to the wavelength in free space at the center frequency, i.e., 38 GHz). In addition to its wideband performance and compactness, highlights, including a stable gain of around 5.5 dBi, low backward radiation, and low cross polarization, are also achieved. In particular, the proposed design outperforms most state-of-the-art millimeter-wave endfire antennas with a notable bandwidth.