Design and Investigation of Differential-Fed Ultra-Wideband Patch Antenna with Polarization Diversity

A novel single- or dual-polarized ultra-wideband (UWB) patch antenna fed by coupled feeding mechanism is proposed. The single-polarized antenna consists of a square ring patch and two ?-shaped patches which are coupled to the radiating patch. The vertical portions of the ?-shaped patches are connected to the microstrip lines which are printed on the bottom layer of the grounded FR4 substrate. To realize the differential feeding mechanism for enhancing the polarization purity, a tapered balun is employed to excite the antenna. Further to provide dual linear orthogonal polarizations, another pair of ?-shaped patches is added in the single-polarized UWB antenna. The dual-polarized UWB antenna prototype can achieve two orthogonal polarizations with an impedance bandwidth (?dB) of 113% and isolation of over 25?dB across the entire frequency band.