International audienceA wideband circularly polarized, four-arm Archimedean spiral antenna backed by a low-profile metallic cavity of 15 mm (0.03λ at the lowest frequency) with a 8:1 bandwidth from 0.6 GHz to 5 GHz is presented. A feed network comprising of a 90° wideband hybrid connected to two 180° hybrids excites the spiral antenna in the fundamental mode. For the entire 8:1 bandwidth, the measured input return loss of the system is more than 11.4 dB. Despite the low-profile cavity, the measured boresight gain and axial ratio of the antenna is -1 to 8.7 dBi and less than 2 dB respectivel
International audienceA wideband dual-polarization, low-profile cavity backed four-arm Archimedean spiral antenna is first presented. This is further extended to a linear array of spiral antennas. Beamforming capability of the linear array for both polarizations is measured and presented for a 4:1 bandwidth
International audienceA wideband dual-circular unidirectional four-arm Archimedean spiral antenna operating from 0.6 to 2.4 GHz is presented. Without a cavity, the antenna radiates bi-directionally and the dual-circular polarisation of the spiral antenna at boresight is limited to a frequency range from 0.6 to 1.5 GHz. After adding a low-profile, 15 mm deep metallic cavity, the dual-circular polarisation at boresight is extended to more than 2.4 GHz and uni-directional radiation is realised. The four-arm spiral antenna is excited through a feed network consisting of a wideband four-way power divider and four wideband digital 2-bit phase shifters. This feed network facilitates instantaneous switching between right hand circular polarisation and left hand circular polarisation. The measured input return loss of the system is more than 10 dB for the entire two-octave bandwidth. The measured boresight gain from 0.6 to 2.4 GHz is −2.8 to 11.2 dBi and −3.1 to 8.7 dBi for RHCP and LHCP, respectively
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