Wideband circularly polarized patch antenna using broadband baluns

Abstract

A novel 90° broadband balun comprising a broadband 90° Schiffman phase shifter is introduced as a means of enhancing the wideband circular polarization performance of dual-fed type microstrip antennas. The proposed 90° broadband balun delivers good impedance matching, balanced power splitting and consistent 90° (±5°) phase shifting, across a wide bandwidth (∼57.5%). A circular patch antenna utilizing the proposed 90° broadband balun is shown to attain measured impedance S11 < -10 dB) and axial ratio (AR < 3 dB) bandwidths of 60.24% and 37.7%, respectively, for the dual L-probe case; and 71.28% and 81.6% respectively, for the quadruple L-probe case. © 2008 IEEE.