Halved Vivaldi Antenna With Reconfigurable Band Rejection

This letter presents a Vivaldi antenna having the capability of dynamically rejecting interferers, mainly aiming at multistandard communication with dynamic frequencies allocation. Only half of the Vivaldi is used and placed over a ground plane, which is suitable to vehicular communication. The rejection filter is integrated to the antenna real estate and consists of two microstrip resonators and two varactor diodes coupled to the slot of the Vivaldi. It is simply biased by applying the control voltage at the antenna RF port. Good matching is achieved from 2.5 to 8 GHz while rejecting a band whose central frequency can be tuned from 1.8 to 5.8 GHz. Simulated and measured return loss, gain, and radiation patterns are presented. The measured gain rejection in the direction of the radiation maximum is about 20 dB or better in the entire tuning range.