Log-periodic slot antenna with modified cavity

A cavity-backed log-periodic slot antenna which operates in 1-4.5GHz is presented. The antenna is fed by a special coplanar waveguide(CPW) that is gradual-changed and ultrawideband matched. Normal cavity is a high-Q resonator and will break the resonance of the antenna, especially at lower frequencies. A novel design of the cavity here is proposed to yield desired VSWR characteristics which is below 2.5 through the whole operation frequency band. The radiation patterns are unidirectional and quite stable within the band, which makes the antenna suitable for the applications in guidance, detection and UWB radar.