Yagi-Uda-Inspired Pattern Reconfigurable MIMO Antenna with Suppressed Harmonics and Minimum Parasitic Presence for WLAN Applications

In this paper, a dual port multiple-input-multiple-output (MIMO) antenna with pattern diversity, integrated with a low pass filter to eliminate higher order harmonics is presented. The operating principle of the prototype is similar to that of Yagi-Uda antennas where multiple parasitic elements loaded with single or multiple switches are utilized to achieve the desired radiation characteristics. In the present design, however, only a single parasitic element loaded with just one switch is used to obtain six different H-plane radiation patterns within 2.4GHz WLAN band (2.4GHz-2.48GHz). Since the proposed antenna has less parasitic involvement, spurious ohmic losses are also minimized. The low pass filter, integrated with the microstrip feedline of the radiator, can suppress the higher order harmonics (atleast upto 11GHz) as well as simplifies the back-end circuitry of the whole MIMO antenna system itself. The prototype is fabricated on FR4 glass epoxy substrate with 1.6mm thickness.