Highly-Isolated Unidirectional Multi-Slot-Antenna Systems for Enhanced MIMO Performance

In this article, an improved approach is presented for designing Electromagnetic Bandgap (EBG) reflectors for slot antennas by using a waveguide aperture source in simulating reflection phase test. In this manner the nonplanar nature of the near field at the location of the source, that is, antenna, as well as its loading effect on the reflector are incorporated in the design of a mushroom-type EBG structure operating at 5.3 GHz. This EBG design performs as an efficient reflector in normal wave incidence while suppressing the substrate-bound modes propagating in the azimuthal directions. The designed EBG reflector is employed in several two-slot-antenna structures to establish excellent antenna isolation of at least 25 dB and single antenna gain of 5 dB at 5.3 GHz in each scenario. To further reduce coupling, the antennas are reoriented to benefit from polarization mismatch and radiation pattern nulls, resulting in isolation values of above 40 dB for antennas spaced one wavelength apart. The two-antenna structures are also characterized for MIMO performance in a reverberation chamber and demonstrate an impressive diversity gain of better than 8 dB in a rich multipath environment. (c) 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:289-297, 2014.