A Low Profile High Gain Ultra Lightweight Circularly Polarized Annular Ring Slot Antenna for Airborne and Airship Applications

In this paper a low profile circularly polarized annular ring slot antenna (CPARSA) with high gain is presented. An inverted U-shaped meandered slot is cut at the inner patch of annular ring to obtain the circularly polarized (CP) radiation. This annular slot loaded ground plane on a substrate thickness of 0.5 mm results in a very low profile (0.009λ
₀
) antenna in term of free space wavelength at its center operating frequency. The largest side lengths of octagonal shaped antenna are 0.89λ
₀
× 0.89λ
₀
according to its center frequency. Measured impedance bandwidth of 23.54% from 5.4 GHz - 7.0 GHz (for |S
₁₁
| ≤ -10 dB) and AR bandwidth (AR<; 3 dB) of 5.15% from 5.67 GHz - 5.97 GHz are achieved by the antenna. Meanwhile, stable radiation pattern is observed throughout the entire bandwidth with peak gain of 7.6 dBi at the center frequency of 5.8 GHz. A defected ground plane is employed in the design which results in reduction of surface waves leading towards higher gain of antenna. The proposed antenna operating at 5.8 GHz band is fabricated on low cost substrate with standard printed circuit board (PCB) process. The proposed design provides favorable characteristics for various lightweight applications including miniaturized drones and airborne applications. To validate the prototype, measured results are compared with simulation outcomes and good agreement is obtained.