Multiband MIMO antenna using a symmetric slotted structure for next generation USB dongle application

A compact multiband MIMO antenna using a symmetric slotted structure is proposed for next generation USB dongle applications. The proposed MIMO antenna consists of two triple-band PIFAs with a symmetric slotted structure. The first resonance frequency is controlled by the total length of the main radiating strip with coupling slits (slit 1 and slit 2), which has a length of 70 mm (about 0.18 wavelengths at 0.77 GHz). The second one can be obtained by inserting on additional slit (slit 3) for WCDMA band. Moreover, the third resonance frequency can be tuned by the width of coupling slits (slit 1 and slit 2) and the position of the port 1 and 2 (P₁ and P₂) to cover M-WiMAX Band (2.5-2.69 GHz). To obtain a high isolation characteristic between two antennas, a symmetric slotted structure and the jointed shorting line are used to reduce the interaction between the two PIFAs. The proposed MIMO antenna has an isolation of approximately 15 dB and the envelope correlation coefficient (ECC) of the two antennas is less than 0.2 over the whole wanted frequency bands.