A Dual Band Circularly Polarized Antenna with Suppressed Harmonic for Tansponder System

Abstract

In this paper, a dual band circularly polarized antenna is designed to operate in S - and C -band by stacking the C-band patch and feed network on top of the S-band patch and feed network. To lower long feed line inductance, lower patch is taken as ground for top radiator and top feed network. To suppress the second harmonics of S-band radiator, its feed network is modified by adding a pair of shorted quarter wavelength stubs. To increase the mechanical stability and robustness of the antenna structure, radiating patches are supported with foam, covered by a Teflon radome and placed in a cylindrical metallic cavity enclosure. The designed dual band circularly polarized antenna provides 10 dB impedance bandwidth (BW) of 15.5% at 2.8 GHz and 25.8% at 5.65 GHz and 3dB axial ratio BW of 8.3% at 2.8 GHz and 22.5 % at 5.65 GHz with a peak gain of 7dBi and front to back ratio of more than 23 dB over the BW. The designed antenna can be integrated with a missile to monitor its trajectory and health parameters. © 2025 IEEE.