Equiangular Spiral Antenna Design Embedded in a Launcher Fuselage for S-Band Communications

An improved equiangular spiral antenna with circular polarization is proposed as the radiating element for a phased array antenna intended for new generation space launchers. The spiral has been designed in printed technology to achieve a low-profile configuration capable to be embedded in the launcher fuselage. The bidirectional radiation of the spiral is converted into unidirectional by introducing the antenna in a metallic cavity. Furthermore, an absorber ring is added inside to maintain the radiation characteristics of the antenna without increasing its size as well as to adjust the axial and impedance ratio produced by the cavity. The antenna has been simulated and fabricated to validate its performance. Besides the array will operate from 2.0 to 2.3 GHz, wideband results of the spiral antenna have been obtained. The antenna, with a diameter of 0.6 wavelengths at 2.0 GHz, provides a 52% relative bandwidth (2.0-3.4 GHz) with a pure circular polarization.