Low-Profile, Small Circularly Polarized Inverted-L Antenna With Double-Folded Arms

A low-profile and small circularly polarized (CP) antenna is proposed and developed in this letter. The proposed CP antenna consists of two modified linearly polarized (LP) inverted-L antenna (ILA) elements with double-folded arms. The double-folded structure plays a significant role in improving impedance matching and radiation characteristics. By properly adjusting the lengths of two arms, quadrature currents can be produced on two orthogonal elements so that circular polarization is achieved. Since the proposed LP elements are low-profile and small in size, the proposed CP antenna is minimized to be about λ0/4 in lateral size and λ0/7 in height. In addition, the feeding configuration is simplified by using only a short vertical probe instead of an external polarizer. Good agreement is obtained between the simulated and measured results, which validate our design concept. The measured results show that the fabricated CP antenna has a wide impedance bandwidth (VSWR <; 2) of 10.4% and a 3-dB axial ratio (AR) bandwidth of 2.92%.