Low-Profile Meandering Spiral Antenna Using an Absorber-Loaded EBG Cavity

This paper presents a meandering spiral antenna (MSA) with a compact absorber-loaded electromagnetic band gap (EBG) cavity. The novel EBG structure features unit cells that are implemented using two substrates connected with vias through an air gap. Inserted in the air gap is a thin layer of RF-absorbing foam utilized to improve the axial ratio bandwidth compared to an absorber-less EBG structure. The design utilized the EBG to achieve a very low cavity height of 12.8 mm which is <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.16 \lambda$</tex> at the lowest operating frequency of 3.8 GHz. Despite this compact size, the antenna maintains key performance parameters including a reflection coefficient below -10 dB from <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$3.0-8.0 \text{GHz}$</tex>, RHCP gain exceeding 0 dBic from <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$3.0-7.9 \text{GHz}$</tex> (peaking at 4.8 dBic), and an axial ratio below 3 dB from <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$3.8-6.6 \text{GHz}$</tex>. The proposed design, which combines size reductions from the MSA and hybrid EBG structure, is an innovative solution for broadband spaceconstrained antenna systems.