Planar Quasi-Isotropic Antenna and Its Implementation of Filtering Response

Two planar quasi-isotropic antennas are presented in this letter, and the filtering response is implemented on the second antenna. First, a printed shorted patch which can be equivalent to a magnetic dipole is utilized with a fan-shaped monopole serving as an electric dipole to achieve quasi-isotropic radiation. A lumped capacitor, a pair of near-field parasitic elements and a slot are introduced to improve the roundness. Ultimately, the gain deviation is reduced to 3.5 dB. Furthermore, a half-mode substrate integrated waveguide is applied to achieve the magnetic dipole for the second antenna. The filtering response is obtained by introducing a uniform impedance resonator. A radiation null is obtained above the operating band, whereas a quasi-isotropic radiation is achieved in band with a gain deviation of 7.3 dB.