Design of a MIMO Open-Slot Antenna Module with Dual-Band Circular Polarization

A multi-input multi-output (MIMO) open-slot antenna module with dual-band circular polarization has been presented in this work. Two horizontal and stepped-impedance (SI) open-circuited slot structure as the radiator are etched in the ground plane and two T -shaped microstrip lines as the feeding line are placed above the horizontal open-slots. A vertical and SI open-circuited slot is also embedded in the ground plane to excite circular polarization around 2.4 GHz and to improve mutual coupling between the two horizontal open-slots. To enhance circular polarization at 5-GHz band, two pairs of two closed slots are etched in the upper and lower parts of the ground plane. From the measured results of the proposed antenna module, the −10 dB impedance bandwidths range from1.72 to 3.93 GHz and from 4.67 to 6.39 GHz. In addition, the in-band isolation is larger than 16 dB. The proposed antenna provides dual-band circular polarization, which covers the triple-band wireless local area network (WLAN) applications, including 2.4, 5.2, and 5.8 GHz. The bandwidths of the simulated axial-ratio (AR) values less than 3 dB are 2.21-2.55 GHz and 5.09 – 6.33 GHz.