In the paper, a wideband circularly polarized (CP) filtering antenna is proposed, which is composed of four bent Vivaldi elements excited with sequential-rotated feeding technique. Since the Vivaldi element has the advantages of high gain and wide bandwidth, it is selected as the radiation element. On this basis, two cross slots are etched on the Vivaldi antenna to increase the gain at lower frequency band, and bent method which has less effect on the overall performance is applied for lowing the profile of the antenna. To realize filtering characteristic, the quadrature four-feed network consisting of one modified miniaturized filtering rat race coupler (FRC) and two compact wideband quadrature couplers is utilized as the sequential-rotated feeding for the Vivaldi elements. Design procedures of the Vivaldi antenna, the modified filtering FRC and the quadrature four-feed network are given. For validation, a prototype is fabricated and measured. Results show that more than 60% fractional bandwidth (FBW) is achieved under the criterions of more than 10 dB return loss and less than 3 dB axial ratio. Within the AR bandwidth, the gain is in the range of 7.5 dBic~10.1 dBic. Out of the operation band, the gain sharply decreases to be lower than -5 dBic with a rectangle coefficient (|Normalized Gain-10-dB/Gain0-dB|) of 1.25, which indicates good filtering performance.
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