A Dual Polarization Phased Array with Connected Spirals
R. Guinvarc'h (1), Randy L. Haupt (2)
(1) Supelec/SONDRA, Gif Sur Yvette, France, (2) The Pennsylvania State University, Applied Research Laboratory, State College, PA, USA
A spiral antenna is a broadband element exhibiting circular polarization: right hand circularly polarized (RHCP) or left hand circularly polarized (LHCP) depending on its winding. An array of spirals with dual polarization must therefore have spirals winding both right and left. A simple configuration alternates every other RHCP element with a LHCP element. In that case, the spacing is such that the frequency at which the grating lobes appear (so the maximum frequency of the array) is lower than the minimum frequency of the spiral (and, so, of the array, with a return loss less than -10dB). This paper describes how to modify a spiral array to greatly improve its behavior at low frequency, without modifying the spirals themselves. The technique consists of connecting adjacent cross polarized spirals. Thus, the currents travel from one spiral to the next instead of being reflecting from the end of the arms. In addition, the currents transmitted to the neighboring spirals radiate the same polarization, due to their geometry.
IEEE Antennas and Propagation Society International Symposium (APSURSI)
2010
July
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