Compact metal-printed filtering antenna with wideband performance

In this letter, a wideband cavity-backed filtering antenna based on 3-D printing technology is proposed for millimeter wave applications. This antenna is made up of an air-filled metal cavity, attached with two transverse slots on its upper surface. By exciting one TE110 cavity mode and two slot modes simultaneously, wideband performance can be obtained. Besides, by properly bending one slot into U-shape, two radiation nulls appear at two sides of the passband, yet causing the increase of the cross-polarization in H-plane. To remedy this, the U-shaped slot is further bent at its ends, successfully suppressing the cross-polarization by 7 dB. The final proposed filtering antenna is implemented and measured, showing a wide bandwidth of 37.3%, covering from 21.4 to 31.2 GHz. And the measured maximum gain is 6.6 dBi in band, with two radiation nulls at 14.6 and 40 GHz.