To assistance of several multimedia services, have higher data rate to wireless communication system. The necessity of high bit error rate (BER) wireless communication with high channel capacity and reliability, multiple-input multiple-output (MIMO) system is a desired method. In the multifunctional wireless communication application, MIMO antenna system should have compact structure and high isolation [2]. Numerous technique have been proposed for enhance isolation between the elements of a MIMO antenna because MIMO antenna system requires high isolation. The function of MIMO antenna depends on the inter-element spacing, aperture area, radiation pattern of single antenna element, array geometry and number of antenna elements. However, designing MIMO antenna over wide bandwidth is challenging tasks due to the tradeoff between inter-element spacing and mutual coupling. Mutual coupling and radiation patterns are governed by electrical separation between elements, which varies significantly with frequency over wide bandwidth. Larger inter-element spacing results in lower mutual coupling, but the size of the antenna becomes large which is not …show more content…
The geometry of the proposed MIMO antenna is illustrated in Fig. 1. The MIMO antenna printed of two symmetric U- shaped branch 30mm × 50mm × 1.6mm on FR-4 substrate with partial ground plane and micro strip-fed through ports 1 and 2.The spacing between of antenna elements λ/4(0.270 ) over UWB. Different types of MIMO antenna systems have been proposed for UWB applications. The designed systems show good impedance characteristics in the frequency band of 3.1-
10.6 GHz, Thus fulfilling the FCC requirements for UWB communications. These systems also have very low mutual coupling and correlations, so they provide good diversity performance. These MIMO Antennas are composed of identical stepped patch elements. In fig.8 reflection coefficient of UWB MIMO antenna is presented, there has ≤ -20 dB isolation which resonant at 3.7, 4.7 and 6.4 GHz all over UWB (3.1- 10.6GHz). B. Effect of Ground and Stub
For better isolation over wideband stub in ground proposed for the UWB antenna elements. Due to the inserting stub in ground plane of antenna there is increased in isolation over UWB. Edge to edge separation between elements is d (0.270