Compact, Highly Efficient Huygens Antenna Array With Low Sidelobe and Backlobe Levels

Abstract

An innovative Huygens antenna array is reported. It has a compact cross section and simultaneously exhibits high aperture and radiation efficiencies and low sidelobe level (SLL) and backlobe level. The fundamental system consists of a collinear <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1 \times 4$ </tex-math></inline-formula> magnetic dipole (MD) array unified with an in-phase collinear <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1 \times 4$ </tex-math></inline-formula> electric dipole (ED) array. The MD array is realized as TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5.0</sub> -mode SIW waveguide sections with seamlessly integrated phase inverters. The ED array is accomplished with two metal plates orthogonally connected to the waveguide aperture. Low sidelobes are realized, thanks to a natural magnitude taper of the fields radiated by each Huygens section located further from the waveguide center where its excitation resides. This fundamental array is easily expanded to a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\,\times \,4$ </tex-math></inline-formula> array facilitated by an amplitude-weighted 1-to-4 microstrip feed network. An X-band prototype operating at 10 GHz was fabricated and tested. The measured and simulated results are in very good agreement. The measured <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert \text{S}_{11} \vert $ </tex-math></inline-formula> bandwidth is 570 MHz from 9.63 to 10.2 GHz. The measured realized gain is stable across the entire bandwidth with a 17.5 dBi peak value. All measured SLL and backlobe levels are less than −20 dB. The measured realized aperture efficiency is 67.0% and the simulated radiation efficiency reaches 92%.