Wideband Differentially Fed Circularly Polarized Antenna Array Based on Higher Order Mode Substrate Integrated Waveguide

This paper presents a wideband differentially fed circularly polarized (CP) antenna array based on higher order mode substrate integrated waveguide (SIW). First, a novel CP element is proposed. It employs TE
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mode SIW as the feeding network to realize the differential feed and uses a pair of L-shape-like strips to attain CP radiation. Because of the stable differential characteristic over a wide frequency range provided by the higher order mode SIW, the proposed element is able to achieve a wide axial ratio bandwidth (ARBW) of 18.2%. With the same principle, the design is extended to a 2 × 2 array. Study found that the 3-dB ARBW and gain bandwidth of the proposed array are 17.3% and 24%, respectively. The peak gain is 14.19 dBic.