CPW Feed for Millimeter-Wave SIW-Based Antipodal Vivaldi Antenna

An improved broadband antipodal Vivaldi antenna(AVA) is proposed in this letter. The coplanar waveguide feeds (CPW) are applied and the substrate integrated waveguide (SIW) is used to realize the transition from the coplanar waveguide to the AVA. The antenna size is 79.9mm×24mm. The final design operates over 18-40 GHz with return loss <;_ 10 dB. The antenna gain is relatively stable and the cross-polarization level is lower than -15 dB. It can be used as a feed antenna for millimeter wave imaging systems and can be well matched to various applications of millimeter wave frequencies.