Quad-Band MIMO Antenna Array for Portable Wireless Communications Terminals

A low-profile quad-band antenna array for multiple-inputmultiple-output (MIMO)-enabled wireless communication terminals has been presented in this letter. The proposed dual-element antenna array operates at the following frequency bands: 2.42.5 GHz, 3.43.6 GHz, 5.155.35 GHz, and 5.755.875 GHz. A combination of a C-shaped slot and a T-shaped slit is used to excite three current modes in a conventional single-band planar inverted-F antenna (PIFA). A $ \lambda / 4 $ resonator is integrated into the triband antenna structure in order to get an additional resonance for quad-band operation. The proposed array has been designed over a small ground plane measuring 50$\,\times\,$ 100 mm$^{2}$ , whereas each element in the array occupies a volume of 0.63 cm$^{3}$. Mean effective gain (MEG) and envelop correlation analysis have been used for the array analysis in addition to the capacity and diversity gain measurements in a reverberation chamber. The prototype array exhibits quite low mutual coupling with good input return losses at the desired four frequency bands.