A Wideband Harmonic Suppression Filtering Antenna with Multiple Radiation Nulls

In this paper, a wide harmonic suppression filtering antenna with high selectivity is designed. The filtering antenna adopts dual-layer structures. By introducing four parasitic patches around the top driven patch, the impedance bandwidth is widened. Moreover, the current directions on the driven patch and parasitic patches are opposite in some frequency, so that radiation null is introduced. In addition, a rectangular split ring DGS is etched in the middle of the ground plane, a lower sideband radiation null is introduced. Two sets of dumbbell-shaped defected ground structures are etched on the ground plane of the intermediate layer. The high-order harmonics are suppressed, and another radiation null is introduced. The experimental results show that the antenna operates at 2.46-2.66 GHz; the relative bandwidth is 7.8%; the peak gain is 3.8 dBi; and the S-11 is more than -3 dB at 3-13 GHz.