A Miniaturized Ultra-Wideband Vivaldi Antenna With Low Cross Polarization

A miniaturized ultra-wideband Vivaldi antenna is proposed in this paper. Optimized slots are inserted in the radiation patches to obtain a low frequency resonance. Two substrates with radiation patches are put back to back, forming a double-layered structure. Thus, the transverse E-field of the double-layered structure is significantly reduced due to this symmetric treatment, which gives rise to very low cross polarization. The measured results show that an enhanced impedance bandwidth of approximately 126% in the range of 2.5-11 GHz (S-11 < 10 dB) is achieved. The dimensions of the proposed antenna are 36 mm x 32 mm x 2 mm, and the relative dimensions are 0.3 lambda(0) x 0.26 lambda(0) x 0.02 lambda(0), where lambda(0) is the free-space wavelength at the lowest operating frequency. Furthermore, the cross polarization is 40 dB over the bandwidth. The time-domain behavior of the Vivaldi antenna is tested, and the results show a low cross polarization in the time domain and admirable time-domain responses.