Wideband band-notched monopulse antenna design utilizing differential mode and common mode radiations

This letter proposes a dual-port wideband monopulse Vivaldi antenna based on a new perspective of common mode and differential mode radiations. To realize the sum and difference patterns utilizing the differential and common mode radiations, a metallic wedge is introduced in the center of the Vivaldi antenna, the effect of the virtual magnetic wall disappears, and the realistic electric wall plays the dominant role, fulfilling the boundary condition for difference beam under common mode excitation. Meanwhile, the sum beam is kept unchanged under differential mode excitation. The desired sum and difference radiation patterns are realized in a single Vivaldi antenna under differential mode and common mode excitations, respectively. Moreover, a notched band is introduced for interference suppression, and the notched frequency can be easily controlled by adjusting the microstrip feeding stub without loading an extra resonator. Measured results show that the proposed monopulse antenna exhibits 101 % fractional bandwidth from 2.2 GHz to 6.7 GHz, in which a notched band is from 3.75 GHz to 4.3 GHz. Across the operational band, the average gain of the sum pattern is 8 dBi, and the null depth of the difference pattern is below −15 dB. Measured results agree well with the simulated ones.