Design of balanced CPW-Fed L-shaped CP antenna

Abstract

In this paper, a balanced CPW-fed circularly polarized (CP) antenna is proposed. The antenna consists of two L-shaped monopole radiating elements which are deployed perpendicular to each other to excite orthogonal radiation fields. A 90° delay line section is embedded in one of the differential feedlines to provide 90° phase difference between signals fed to the two input ports. The combination of the above designs were verified to give good CP radiation field patterns. In addition, to suppress the common-mode signals, a half-wavelength CPW line section is connected between the two feedlines for producing a transmission zero in the DM passband under CM operation. For the designed balanced CP antenna, Measurement shows that the |S 11 dd| ≤ −10dB DM operating band covers a frequency range of 2.04–2.87 GHz. Very good CM suppression was observed with the measured CM reflection coefficient greater than −3 dB for 2.1–2.86 GHz. The simulated 3-dB axial ratio band is 2.38–2.54 GHz.