Frequency Reconfigurable Planar Filtering Dipole Antenna with Omnidirectional Radiation Pattern

A frequency reconfigurable filtering monopole antenna with omnidirectional radiation characteristics is presented in this paper. The low-frequency radiation null is introduced by a dumbbell-shaped defect ground structure. The high-frequency radiation null is obtained by adding a V-shaped slot to the monopole radiation arm. The radiation arm is divided in two parts and connected by two varactor diodes. By controlling the capacitance value of the varactor, the equivalent electric length of the antenna is changed, and the function of frequency reconfigurability of the antenna is realized. The reconfigurable filtering antenna has the advantages of small size and low-profile. The test results show that the frequency can be tuned from 2.2GHz to 2.81GHz. The maximum antenna gain is 4.31dBi.