A Circularly Polarized Quasi-Loop Antenna

Abstract—This paper presents a circularly polarized (CP) GPS/DCS loop-like antenna with a microstrip feed. The proposed antenna comprised of a quasi-C antenna, an inverted-L sleeve strip connected with the ground plane and an L-shaped slit embedded in the ground plane. The C-like antenna generates a resonant mode with a poor impedance matching condition. The inverted-L grounded strip and the embedded L-slit are not only capable of modifying two orthogonal electric fields with equal amplitude and phase difference of 90 degree for radiating circular polarization at 1.575 GHz, but the impedance characteristics is also improved and the operating frequency is reduced. Both simulated and measured results are provided to validate the impedance and CP performance of the proposed antenna. For the optimized antenna case, the measured bandwidth with an axial ratio (AR) of less than 3 dB is larger than 19 % and the measured impedance bandwidth of reflection coefficient S11 < −10 dB is about 30.1%. 1.