Wideband Circularly Polarized 1-D Connected Array Antennas with Slant Slot Feeders and Gradient Artificial Dielectric Layers

Abstract

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 z(x)- and z(y)-planes, the guided wave in the slabs exhibits different multipath lengths along the x- and y-directions, leading to a 90 degrees phase difference between the E-x and E-y 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 x 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 frequency-invariant beam pattern with an average half-power beamwidth (HPBW) of 24.77 degrees and a standard deviation below 3.63 degrees over 12-18 GHz for the target pattern, with a HPBW of 26 degrees, demonstrating wideband electronic warfare performance using the proposed array.