A 6:1 Bandwidth, Low-Profile, Dual-Polarized Ring Array of Spiral Antennas With Connecting Arms

In an earlier work, the design of a 2:1 bandwidth dual-polarized phased array of Archimedean spiral antennas with cavity was presented. The reflection coefficient, circular polarization, and grating lobes goals were obtained independently in the design process. The low end of the final bandwidth was constrained to the frequency cutoff of the spiral antenna, at the low end of its bandwidth. In this communication, an extension of the bandwidth of the array is achieved by connecting the spiral antennas of the array. Hence, with the same size, the bandwidth is enlarged almost three times (a total of 6:1). The measurements confirm the simulations. The array can scan up to $\theta=30^\circ$ keeping a low reflection coefficient, good right- and left-hand circular polarization, low-sidelobe levels, and using a low-profile cavity.