Mutual coupling reduction between pattern reconfigurable antenna arrays using electromagnetic band gap

Antenna is a widely used device in wireless communication system to transmit and receive the electromagnetic wave. Sometimes the antenna faces difficulties to perform well with signal reception because of the interferences caused by the unwanted signals. To overcome this problem, the radiation pattern reconfigurable (RPR) antennas have been widely used. This antenna has a capability to alter the radiation pattern which steers towards a desired signal. On the other hand, due to increasing of high demand from the user, researcher came out with multiple-input-multiple-output (MIMO) antenna. This is because, in earlier time the internet and data usage are still new, thus the demand was not high. However, in this new era of technology the internet and data usage increase tremendously and have improved without a limit. Most of the existing research focuses on frequency reconfigurable MIMO antenna that specifically used for mobile terminal application. Limited studies were conducted regarding pattern reconfigurable MIMO antenna. The mutual coupling caused by MIMO system may not only affect the S21 performance, but could further affect the beam steering performance of the RPR antenna. A comprehensive analysis is conducted in the proposed work to identify the challenges of implementing the RPR antenna as MIMO. Hence, this thesis mainly focuses on the following: analyze the beam steering performance of RPR antenna when implemented as MIMO; and to reduce the mutual coupling effect towards the beam steering performance, an hexagonal split ring resonator (SRR) electromagnetic band gap (EBG) is proposed. First, to enhance capability of the antenna to serve more users the RPR antenna is implemented as MIMO, taking RPR-MIMO as the design name. The RPRMIMO antenna is designed to operate at 3.5 GHz with S11 < -10 dB, S21 < -15 dB, steered angle of more than 20° and minimum average gain of 5 dBi at all steered directions. The RPR-MIMO was modelled in, three configurations, namely configuration 1, 2 and 3. From analysis, configuration 3 was identified that gives minimal effect to the RPR beam steering performance and mutual coupling in terms of S21. On the other hand, the proposed SRR-EBG produced band-gap region from 3.3 GHz frequency to 3.6 GHz frequency. The EBG based RPR-MIMO (RPR-MIMO-EBG) helps to improve the steering angle. Then DC biasing was applied to the RPR-MIMO-EBG antenna before fabrication was carried out. The experimental verifications have demonstrated that the measured results agree well with the simulation. The future work may consider implementing the embedded system with the proposed RPR-MIMO to monitor and track the high demand of network user and will serve toward accordingly.