Filtering Antenna With Quasi-Elliptic Response Based on SIW H-Plane Horn

A filtering antenna with a quasi-elliptic response based on the substrate-integrated waveguide(SIW) H-plane horn is presented. It is mainly composed of two symmetrical horn elements embedded with the trapezoidal dual-mode cavity. By exploiting the cross couplings of the dual-mode cavity, two radiation nulls are introduced on the gain curve showing a quasi-elliptic filtering response without the increase of horn size. Then, a modified transition is printed in front of the horn aperture on both sides of the substrate, which acquires wider impedance bandwidth and maintains a low backlobe radiation throughout the bandwidth. Besides, the proposed antenna is designed, fabricated, and measured at Ku-band. Two measured radiation nulls can be observed at 14.02 and 17.98 GHz, where the gain drops significantly to below -28 and -38 dBi, leading to high frequency selectivity. A wide measured impedance bandwidth of 12.2% and a large front-to-back ratio of more than 20 dB are achieved. To the author's best knowledge, it is the first time that the filtering horn antenna with radiation nulls, wide bandwidth, and excellent radiation is designed.