Circularly Polarized Dipole-Loop Antenna

This paper presents a circularly polarized antenna composed of a dipole and a modified square loop structure. A T-type open stub structure is added into each of the two edges which adjoin the feeding side of the square loop. The dipole structure is arranged perpendicularly in the center of the square loop structure. The coplanar strips which are transitioned from CPW, are directly fed into the modified square loop. From the feeding side of the modified square loop, a novel balanced-type using broadside coupling strips is adapted to feed the dipole. For circular polarization applications, the electrical length of the broadside coupled strips circuit is adjusted to produce a phase delay of 90 degrees compared with that of the feeding point of the modified square loop. The simulated and measured results are also shown to demonstrate this design.