Wideband Circularly Polarized Planar U-Shaped Antenna Array for Millimeter-Wave Applications

Abstract

A wideband circularly polarized (CP) planar U-shaped antenna array is presented for millimeter-wave (mm-wave) applications. First, the antenna element consists of two tilted parasitic U-shaped patches fed by a slot etched on a substrate integrated waveguide (SIW). An improved simulated axial ratio (AR) bandwidth of 40% is achieved by stacking the slot and the patch element. Then, the right- and left-handed orthogonal unit vectors and resonant circuit technique are employed to explain the improved CP operating principle. Finally, an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8 \times 8 $ </tex-math></inline-formula> array is achieved based on the CP element, multiple SIW cavities, and a 16-way SIW feeding network using full-corporate scheme. To verify the design, a prototype is fabricated and measured, which demonstrates a wide impedance bandwidth of 40.4%, a wide AR bandwidth of 31%, a peak gain of 24.6 dBic and supporting dual-CP mode character. The proposed antenna array shows excellent performance and a novel structure, making it a promising candidate for mm-wave wireless systems.