A Compact Helix Antenna With Wide Axial Ratio Bandwidth Using a Spiral Microstrip Coupling Feedline for GNSS Applications

Abstract

A compact quadrangular prism-shaped slot helix antenna with wide axial ratio (AR) bandwidth using a spiral microstrip coupling feedline is presented. The proposed antenna is constructed with FR4 substrate copper-clad plate with four slots symmetrically etched on the substrate exterior surface and a spiral microstrip coupling feedline printed on the substrate inner surface. The electric field and equivalent magnetic current excited by the spiral microstrip feedline in slots are analyzed. The wide AR bandwidth is obtained. The proposed antenna has a small dimension of 0.156λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.156 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.182 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the free-space wavelength at the center frequency). Its measured -10 dB |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | bandwidths and 3 dB AR bandwidths are 1525-1662 and 1497-1630 MHz, respectively. It generates right-hand circular polarization (RHCP) without a complicated feeding network. It promises a good use in Global Navigation Satellite Systems.