Dual-band MIMO Antenna Using a Symmetric Slotted Structure for 4G USB Dongle Application

A compact dual-band MIMO antenna using a symmetric slotted structure is proposed for next generation USB dongle applications. The proposed MIMO antenna consists of two printed dual-band PIFAs with a symmetric slotted strip. The first resonance frequency is controlled by the total length of the main radiating strip with coupling slot (W(1) = 2 mm and W(2) = 2 mm) has a length of 70 mm, which is about 0.18 wavelengths at 0.77 GHz, but it can easily generate a resonant mode to cover LTE band 13 (LTE Band 13; 0.746-0.787 GHz) and the second one is tuned by the width of the slot (W(1) and W(2)) and the position of the port 1 and 2 (P(1) and P(2)) to cover mobile world interoperability for microwave access band (M-WiMAX Band; 2.5-2.69 GHz). In order to improve the isolation characteristic at the LTE and M-WiMAX bands, 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 20 dB at LTE band 13 and the envelope correlation coefficient (ECC) of the two antennas is less than 0.2 over the whole LTE band 13. To evaluate the performance of the proposed antenna, key performance parameters such as the total efficiency, ECC, mean effective gain (MEG), MEG ratio and actual diversity gain are analyzed.