Design of a Kind of Combined Antenna with Wide Band for Passive Radar Application

The wide band antenna is a key technique for the passive radar. This paper proposed a new kind of wide band antenna combined with the Archimedean spiral and hemispherical helix for passive radar application. For the new antenna, the planar Archimedean spiral is mounted on the top of the hemispherical helix, and it is fed at the center of the Archimedean spiral. An antenna with specific structure and parameters was designed and simulated to obtain its radiation performances over the operating frequency range from 2GHz to 10GHz. For entire operating frequency range, the simulated gain is greater than 5 dBi and the voltage standing wave ratio (VSWR) is less than 2 when the characteristic impedance of transmission line at the terminal is 240Ω. Wide beam and approximately circular polarization characteristics are also observed. The simulation results demonstrate that the new kind of antenna has wide band radiation performances, which can be used in passive radars. Furthermore, the proposed antenna has simple structure and low cost, so it is suitable for mass fabrication.