This paper proposes wideband circularly polarized (CP) 1-D connected array antennas with slant slot feeders and gradient artificial dielectric layers (ADLs). The slant slot feeder introduces an identical electric field (E-field) along the x- and y-directions. Three slabs consisting of multiple ADLs are stacked above the slot feeder. Due to the different boundary conditions of a 1-D connected array in the zx- and zy-planes, the guided wave in the slabs exhibits different multipath lengths along the x- and y-directions, leading to a 90◦ phase difference between the Ex and Ey components. Moreover, the cascaded slabs are designed with gradient effective permittivities for a gradual impedance transition from the guided mode to the radiating mode, allowing for wideband matching and CP performance. To validate the proposed design approach, an 8 × 1 array was fabricated and measured. The antenna shows a 1.96:1 (10.1–20 GHz) impedance bandwidth (VSWR < 2) and a 1.46:1 (12–17.5 GHz) 3 dB axial ratio bandwidth in measurement. The array exhibits an average right-hand CP boresight gain of 12.39 dBic. Moreover, we produced a frequencyinvariant beam pattern with an average half-power beamwidth (HPBW) of 24.77◦ and a standard deviation below 3.63◦ over 12–18 GHz for the target pattern, with a HPBW of 26◦, demonstrating wideband electronic warfare performance using the proposed array.
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