Duong Thi Thanh Tu, Nguyen Gia Thang, Nguyen Thi Bich Phuong, Vu Van Yem

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A structure, the proposed MIMO antenna is compact in size and designed on FR4 substrate with total dimension of 37 x 43.6 x 6 m3. At first, a single PIFA antenna is presented using U-shaped slots in radiating patch which puts forward the antenna resonant in three frequencies: 2.4GHz, 3.5GHz and 6.3GHz with bandwidth of 8.87%, 18.29.% and 2.53 % respectively for Wi-Fi, Wimax/LTE and Direct Broadcast Satellite DBS of C channel applications. Good reflection coefficient, antenna gain, and radiation pattern characteristics are obtained in the frequency band of interest.  Secondly, the paper has put forward another single type of tri-band PIFA which uses double rectangular shape of Defected Ground Structure (DGS) technology. This helps increasing the antenna efficiency at all frequencies as well as enhancing antenna gain of the PIFA. Finally, a MIMO PIFA antenna is constructed by placing two single antennas side by side at close distance of 4 mm. The MIMO antenna also gets high gain and radiation efficiency at all frequencies. To reduce the mutual coupling between antenna elements, a combination of two “slot and variation” structures of DGS is proposed. Moreover, these DGS structures have enhanced MIMO antenna bandwidth at all three bands, especially at 3.5GHz resonant frequency.