Reduction of Correlation Coefficient Using Frequency Selective Surface for Multi-band MIMO Antenna

Abstract

Multiple-Input Multiple-Output (MIMO) system is an important enabling tech nology for the current 4G and 5G systems to achieve reliability and high data rates. Also, due to the size limitation in today’s communication systems, MIMO plays an important role in achieving the required data rate and throughput by placing multiple antenna elements in a single package. It also mitigate fading effects in communication systems because of availability of multiple channels. Among the other parameters, correlation coefficient (CC) is one of the important evaluation parameters for a MIMO system. CC accounts for the correlation induced among the channels of MIMO system due to radiation patterns of the antenna elements. For better performance in MIMO systems, a low value of correlation coefficient is desired. Achieving a low value of CC for antennas in a small form factor is a challenge for antenna designers. Communication systems are becoming compact and compact with each passing day, with increase in limitations of size. To cater for these limitations multi-band antennas has been in use as a solution. As one multi-band antenna is equal to two single band antennas of different frequencies. Moreover data can be transmitted at different frequencies using a single multi-band antenna through which the data rate can be increased. So, this increase the need and necessity of multi-band antenna in today’s communication systems. Recent literature shows that a lot of work is ongoing to reduce the value of CC. One of the efforts focused on decreasing the value of CC, by altering and de-correlating the radiated fields of radiating elements for single band MIMO antenna. This thesis presents a design for reduction of CC for a multi-band MIMO antenna configuration. The presented design includes a dual-band Frequ (FSS) placed upon a dual band MIMO antenna in a Fabry-Perot (FP) cavity configuration, to tilt the beam of antenna elements away from each other hence de-correlating the radiated fields. The operating frequencies of presented design are 2.8 GHz and 5.6 GHz. Full wave simulations along with measurements of fab ricated prototype are performed. CC reduction was observed in both frequency bands. Maximum reduction of 73.4% in CC value is achieved by placing partially reflective surface (PRS) over multi-band MIMO antenna . The design is suitable for applications in sub 6-GHz 5G and WLAN frequency bands