A Compact Wideband Circularly Polarized Antenna Array for $C$ -band Applications

In this letter, we present a compact single-layer microstrip antenna array for applications in the C-band. The device is designed and fabricated with an overall volume of 45 mm × 45 mm × 1.6 mm, (0.86 λ0 × 0.86 λ0 × 0.03 λ0 at a frequency of 5.75 GHz), a suitable dimension for compact handhelds. The proposed array is based on a modified sequential phase network, composed of nonuniform curved transmission lines, feeding a set of 2 × 2 disc based patch elements. The proposed network has space-filling properties, and is arranged in the unoccupied area between the elements, minimizing the overall dimensions without sacrificing the operating bandwidth. Adequate agreements between the simulated and measured results validate the proposed design: a 3-dB axial ratio band of 900 MHz, meaning 15.5%, a peak gain of 8.25 dB maintained within 3 dB for 1.2 GHz, and a very wide 10-dB return loss bandwidth of 29%. This performance is unmatched for the given dimensional constraint with a single-layer via-less technology .