Isolation and Gain Improvement of Multiple Input Multiple Output Antenna Using Frequency Selective Surfaces

Abstract

|This letter addresses a new approach to improve the gain and isolation of a multiple input multiple output (MIMO) antenna. A C-shaped printed antenna with both ends terminated by a small rectangular section is designed as the basic antenna element for a 2 element MIMO antenna of size 0 : 8 (cid:21) (cid:2) 0 : 67 (cid:21) (cid:2) 0 : 04 (cid:21) ( (cid:21) , corresponding to the lowest operating frequency) which operates over the X band with the peak gain of 3 dBi. By introducing a double layered frequency selective surface (FSS) of unit cell dimension 0 : 2 (cid:21) (cid:2) 0 : 2 (cid:21) (cid:2) 0 : 0375 (cid:21) between the two antenna elements as an isolation wall and additionally by placing a 5 (cid:2) 3 array of FSS geometry as a re(cid:13)ector below the antenna, the isolation and gain of the two element MIMO antenna are improved by 37 dB and 3 dBi, respectively. The proposed FSS loaded MIMO antenna provides very high isolation about (cid:0) 51 dB (measured) and a very low envelope correlation coefficient (ECC) of 0.000177282 (simulated) using far (cid:12)eld approach and 0.000000033414 (calculated measured) using scattering ( S ) parameter approach. Further, MIMO parameters like diversity gain (DG), total active re(cid:13)ection coefficient (TARC), mean effective gain (MEG), and channel capacity loss (CCL) have been evaluated. The radiation pattern is unidirectional in nature with a peak gain about 6 dBi. The letter also presents detailed design guidelines for the proposed FSS loaded MIMO antenna along with their veri(cid:12)cations for Ku and K bands. The proposed structure can also be scaled up to a 4 element MIMO antenna.