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This letter introduces a novel four-arm planar spiral antenna which provides a perfect circular polarization radiation for Global Navigation Satellite System applications. The antenna mainly consists of four parts: an Archimedes spiral radiation area, an impedance matching area composed of an appropriately sized metal coupling disc and quasi-coaxial structures, a wideband four-output-ports feed network with equal magnitude and consistent 90&#x00B0; phase shift, and a set of chokes with unequal height. The metal coupling disc and quasi-coaxial structures are used as an impedance transformer to provide broadband matching between the <inline-formula> <tex-math notation="LaTeX">$50\Omega $ </tex-math></inline-formula> input impedance and the high impedance of the radiation area. The novel choke can ensure the radiation characteristics and stable phase center of the antenna in broadband range. Based on these designs, the proposed four-arm planar spiral antenna shows the impedance bandwidth (VSWR &#x003C; 1.5) and 3-dB axial ratio bandwidth of 1.1&#x2013;1.7GHz, and simultaneously realizes radiation gain greater than 7.4 dBic and phase center deviation (PCD) less than 1.5mm.

A Novel Four-Arm Planar Spiral Antenna for GNSS Application