A Compact Eight-arm Spiral Slot Antenna with Cross-coupled Feeding

keywords:coupling feeding  crossed dipole  eight-arm spiral slot antenna  satellite navigation terminal  circular polarization

Abstract:A compact cross-coupled feed eight-arm spiral slot antenna for satellite navigation terminal is proposed. Eight slit spiral arms are used as the radiating units of the antenna and are etched on the outer surface of a square columnar structure formed by an FR4 dielectric substrate. The feed network is a cross-dipole microstrip line structure with upper and lower mutually orthogonal three-quarter circles, which extends to the outer surface to realize cross-coupled feed. The size of the antenna is 0. 082 λ0 × 0. 082 λ0 ×0. 130 λ0(λ0 is the free-space wavelength corresponding to the center frequency of 1. 561 GHz), and the test results show that the antenna has a -10 dB impedance bandwidth of 1. 554 GHz~1. 591 GHz and a 3 dB axial ratio bandwidth of 1. 535 GHz~ 1. 594 GHz. The gains reach 2. 56 dBi and 2. 75 dBi at the center frequency of the Beidou navigation satellite system B1 band (1. 561 GHz) and the center frequency of the global positioning system L1 band (1. 575 GHz), respectively. The antenna adopts a structure combining a crossed dipole arm coupled feed and an eight-arm slit helix to achieve a better circular polarization performance with broadband and compact size characteristics.