Broad beamwidth and circularly polarized microstrip antenna with parasitic dipoles

To broaden the beamwidth of microstrip antenna (MSA), a method of loading parasitic dipoles is proposed. Its equivalent analysis model has been proposed based on the cavity model. Numerical results reveal that the dipole can act as director or reflector according to its length and the distance between the patch and dipole. Then, the effect of parameters of a pair of parasitic dipoles on beamwidth is discussed. Finally, a circularly polarized antenna with broad beamwidth working at 8.7 GHz is designed as an example. The simulated results show that the 3dB beamwidth of the proposed antenna is 144° and good circularly polarized performance can be obtained.