Two Decoupled LTE Low-Band Conjoined-Loop MIMO Antennas along the Short Edge of the Metal-Framed Smartphone

Two decoupled antennas to suit in the short edge of the metal-framed smartphone with a continuous frame section of 72.4 mm (approximately 0.22 λ at 900 MHz) are presented. The two conjoined-loop antennas are used for multi-input multi-output (MIMO) operation in the long-term evolution (LTE) low band for 880 MHz ~ 960 MHz. The two metal-frame MIMO antennas share a common capacitor-loaded shorting strip to the system ground plane of the smartphone. The addition of a capacitor in the shorting strip is able to decrease the mutual coupling between the two conjoined-loop MIMO antennas, which results in good isolation in the LTE low band. Details of the two conjoined-loop LTE low-band MIMO antennas are addressed. Experimental results of the fabricated antennas are also discussed.