A Low-Profile and High-Aperture-Efficiency Hexagonal Circularly Polarized Microstrip Antenna Array

Abstract

In this letter, a high-aperture-efficiency (η <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">AP</sub> ), right-hand circularly polarized (RHCP), sequentially rotated hexagonal microstrip antenna array, working at GPS L1 band, is proposed. The proposed antenna design is placed on the hexagonal top of a floating sensor node for ocean and marine monitoring applications. To use the hexagonal area effectively and maximize the η <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">AP</sub> , CP microstrip antenna elements have been distributed centrosymmetric about the origin on the hexagonal substrate. Typically, the η <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">AP</sub> is enhanced by using thicker substrates, particularly with air gaps. Here, we show a high η <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">AP</sub> on a very low-profile substrate (0.011 λ for the lowest operating frequency) by properly choosing the distance of the antenna elements from the center of the array. The proposed design, based on H-shaped aperture-coupled circular patches, demonstrates a measured gain of 12.4 dBi and an η <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">AP</sub> of 101%, which is one of the highest reported η <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">AP</sub> for one of the lowest profile sequentially rotational array.