A Tilted-D-Shaped Monopole Antenna With Wide Dual-Band Dual-Sense Circular Polarization

In this letter, a tilted-D-shaped monopole antenna with wide dual-band dual-sense circular polarization is proposed. The tilted-D-shaped radiator is designed by combining the inverted-C-shaped (ICS) and tilted-I-shaped (TIS) structures. The proposed radiator is attached to a 50 Omega line through an impedance transformer. The proposed design is compared with two of its variants, which concludes that the wide 3 dB axial ratio bandwidth (ARBW) in both bands is achieved due to the contributions from the ICS and TIS structures. Besides, the lower and upper bands radiate left-handed circular polarization and right-handed circular polarization, respectively. A prototype of the proposed antenna is fabricated, and its performance is experimentally verified. The measurement results show that the proposed antenna exhibits a wide impedance bandwidth for vertical bar S-11 vertical bar < -10 dB of 104.54% (3.47-11.07 GHz) entirely covering both circularly polarized bands with 3 dB ARBWs of 31.16% (4.28-5.86 GHz) in the lower and 22.62% (7.49-9.4 GHz) in the upper band. In broadside direction, the measured gain varies between 1.26-3.58 dBic and 3.85-6 dBic in the lower and upper bands, respectively.