Circularly Polarized Slot-type MIMO Antenna for USB Dongle Applications

Abstract

Here we have proposed an L-shaped slot-type MIMO antenna with pattern and circular polarization diversity for WLAN applications. In order to maintain low profile, the pattern and polarization diversities have been achieved without using additional supporting structures. Both the antenna elements have been located at the corners of the same side of the ground plane. One of the antenna elements produces left hand circularly polarized (CP) waves whereas the other element produces right hand CP waves in (front) +z-direction. The sense of polarizations are opposite in (backward) –z-direction. CP waves have been generated using the two orthogonal current modes, excited by locating the slot on the corner of the ground plane. The quadrature phase difference between the modes has been employed using the slot geometry. In other directions, the antenna correlation has been reduced using pattern diversity. The measured results confirm the simulation results. The measured axial ratio bandwidth (< 3dB) and the matching bandwidth (<−6dB) were 380 MHz and 110 MHz, respectively. The envelop correlation coefficient was less than 0.1 in the operating band.