Compact Quad-band MIMO Antenna Array with Low Mutual Coupling for Mobile Terminal

A low mutual coupling multiband two element antenna array for the mobile terminal is proposed. This array consists of two symmetrical antenna elements with grounded branches and a slot in between the microstrip feed lines in the ground plane. The working mechanism is explained by analysing the S-parameter and surface current plots. The measured -10 dB impedance bandwidth of a fabricated prototype covers from 824-894 MHz (GSM850), 1427.9-1495.9 MHz (LTE1500), 1575.42 MHz (GPS-LI), 1710-1880 MHz (GSM1800), 1850-1990 MHz (GSM 1900), 1921-2170 MHz (UMTS), 3400-3600 MHz (LTE- 42), 3550- 3700 MHz (CBRS-citizen broadband radio services), 3600-3800 MHz (LTE-43), 4800-5000 MHz (proposed for 5G), 5725-5875 MHz (WLAN -5.8 GHz) and 5855-5925 MHz (V2X) band. Mutual coupling in all the frequency bands is found to be less than-16 dB while maintaining 27 mm (0.076 times free space wavelength at 850 MHz) edge to edge inter-element spacing. The measured S-parameters and radiation patterns are found to be matching with the simulated results.