Design of Vivaldi antennas with embedded reconfigurable stopband filter

This paper addresses the design of Vivaldi antennas with embedded reconfigurable stopband filters, to allow simultaneous multi-standard communication while rejecting interferers. Three designs targeting different band stop bandwidths are presented, all of them featuring wideband matching and large rejection-frequency tuning range. The bandstop filters are formed by microstrip resonators coupled to the Vivaldi slot and terminated by varactor diodes. The major benefits of this solution are a continuous reconfiguration of the stopband, the absence of DC bias network, a quasi zero DC consumption, and the fact that resonators and diode ohmic losses positively contribute to the filtering capability. For the potential use in vehicular communications a halved Vivaldi placed over a ground plane is proposed, but the same concept directly applies to standard complete Vivaldi antennas.