Greetings, In continuation to the above, I look forward for clarifications on the abrupt reason behind the degradation in the efficiency parameter of MIMO antenna post usage of metamaterial as isolation element in MIMO antenna to, prior usage of the same in MIMO antenna is awaited. since, it is well know fact that the performance of MIMO antenna with usage of decoupling element will be good comparing to the one without using the same. But, in many articles come across that the efficiency parameter alone seems to be poor in MIMO antenna with usage of decoupling element (especially metamaterial as decoupling element, but not restricted with metamaterial alone) comparing the one without usage of decoupling element. Discussion with appropriate reference articles are awaited.