Compact Wide Upper Stopband Suppression Filtering Antenna for Aerospace Applications

This article presents a novel wide stopband suppression millimeter wave (mmWave) filtering antenna (filtenna). A three-order resonance substrate integrated waveguide (SIW) topology structure, including a driven patch and a radiation patch, is applied to enhance the bandwidth. In contrast to traditional stacked patch antennas, this design modifies the driven and radiation patches in different shapes. The full mode SIW (FMSIW) cavity is adopted due to its high-quality (high-Q) factor, which effectively improves the antenna’s selectivity. Besides, the generation of main upper band radiation nulls is attributed to the designed FMSIW cavity. Four parasitic vertical dumbbell structures are added to increase the stopband bandwidth. A pair of U-shape slots are etched on the driven patch to generate a lower band radiation null. A polycyclic structure rather than a single radiation patch can generate another lower band radiation null. To reduce the effect of the antenna element on the ground area and increase the isolation between elements, a via array is added around it, which also slightly enhances the sideband suppression of the antenna in the upper sideband. For verification, a filtenna working for the N258 band (24.25–27.5 GHz) is designed, fabricated, and measured. The measured results show that a measured −10-dB impedance bandwidth covering from 24.25 to 29.06 GHz is successfully implemented. The average realized gain can reach 5 dBi, and the lower and upper band suppression can reach more than 30 and 19.1 dB, respectively. Furthermore, the upper stopband achieves wide suppression from 30 to 50 GHz. Overall, this filtenna is a competitive candidate for 5G mmWave applications.