This article proposes the design of a three-layered balanced circularly polarized (CP) antenna using two tightly stacked conventional single-ended CP slot antennas. With a 180° delay line inserted into one of the two feeding microstrip lines that form the balanced feedline, differential-mode (DM) input signals can excite CP radiation in the broadside directions with a measured (simulated) axial ratio of as low as 1.3 (0.86) dB. Common-mode (CM) input signals can be well rejected with a measured (simulated) CM return loss of <0.4 (0.5) dB in the DM impedance band. In addition, only a very small proportion of the CM (DM) input signal is converted into a DM (CM) reflected one. These nice properties of the possibly first reported balanced CP antenna were all achieved without placing before the radiation element a CM-suppression filter.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Atomic and Molecular Physics, and Optics
- Condensed Matter Physics
- Electrical and Electronic Engineering