A Compact Low Profile Wideband CP Antenna Using MM-TL Feeding Network

The design of a wideband circularly polarized (CP) antenna with a very compact size of 0.7808λ
₀
×0.7808λ
₀
operating at the frequency of 2.4 GHz is presented. The antenna consists of a feeding network and four meandered monopoles on a substrate. The feeding network is designed using Wilkinson-power dividers and metamaterial transmission line (MM-TLs) to produce four output signals with equal power and sequential-phase difference of 90°. The four monopoles are placed in orthogonal positions and connected to the outputs of the feeding network to produce a CP signal. The wideband CP antenna is studied and designed using computer simulation. For verification, the antenna is also prototyped and measured using the Satimo Starlab system. The results in impedance bandwidth (IMBW), axial-ratio bandwidth (ARBW), radiation patterns and realized boresight gain are presented. Measured results show that the CP antenna has a very wide IMBW of 0.96~3.69 GHz (117.4%) and ARBW of 1.13~3.58 GHz (104.03%), which are larger than those of all designs found in literature, yet having a very compact size and low profile.