A Filtering Patch Antenna With Flexibly Controllable Radiation Nulls

A filtering patch antenna with flexibly controllable radiation nulls is investigated in this letter. By implanting a band -stop structure on the microstrip antenna, filtering function is acquired. Firstly, the F-type probe structure is proposed, which feeds the microstrip patch to form cross-coupling. A lower out-band null is generated. Subsequently, (Defected Ground Structure)DGS is implanted in the antenna. By changing the current distribution on the metal ground, the upper radiation null is generated and the out-of-band radiation is suppressed. Two radiation nulls are flexibly controlled by different units, and there is almost no interference between them. For demonstration, a prototype is fabricated and measured. The simulation results are in great agreement with the measured values. The antenna operates at 2.33 GHz and achieves a gain of about 7.1dBi in the flat band. The relative bandwidth is 9.8%, and the out-of-band suppression level is greater than 24 dB.