Design of a Low-Profile Omnidirectional Dipole Antenna with Filtering Function

A low-profile omnidirectional dipole antenna with filtering function is presented. The proposed antenna consists of a dipole patch antenna, feeding network with slots and parasitic structure. An open stub and a U-shaped slot are elaborately designed so as to realize filtering function. The open stub is used be a stepped impedance resonator (SIR) to generate radiation null at the upper band while the U -shaped slot is used to realize high pass filtering. It exhibits the impedance bandwidth can reach 45.2% (from 3.18 to 5.04 GHz) by using the proposed method. The proposed antenna has a gain variation in the passband, with a peak gain of 2.44dBi. Two radiation nulls are generated at lower and upper stopband which can reach 25.9 dBi and 18.3 dBi. Moreover, it also maintains uniform omnidirectional radiation characteristic and low cross-polarization characteristic.