This work introduces a novel design for a circularly polarized monopolar microstrip antenna with an omnidirectional conical-beam radiation pattern. The antenna consists of hexagonal quasi-circular patches on the top plane, complemented by asymmetric trapezoid slots on the ground, all implemented on an FR4 substrate without the need for shorting vias. By integrating rotated asymmetric trapezoid ground slots, the antenna induces the degeneration of two adjacent TM02 resonant modes, resulting in a significant 10 dB impedance bandwidth covering 590 MHz, representing a 9.7% fractional bandwidth. The antenna achieves a radiation pattern characterized by successful Right-Handed Circularly Polarized (RHCP) co-polarization and axial ratio close to 3dB at the center frequency of 6.02 GHz. The parameters have been optimized using the finite element method-based full-wave electromagnetic simulator Ansys HFSS, ensuring precise design considerations for enhanced performance.

asymmetric trapezoid ground slots,axial ratio,circular polarization