Left handed materials which have both negative permittivity and permeability, have been the area of potential research over a decade. This paper elucidates antenna parameter optimization using Double Negative Group (DNG) Electric SRR, having 19.13 THz as resonant frequency forming metamaterial array embedded in antenna substrate at high frequency (THz). Ansoft HFSS has been used to design and analyse the RMPA (Rectangular Microstrip Patch Antenna) with design frequency 22.5 THz and operating range of 20 THz to 25 THz having FR4 (εr = 4.4) as substrate material. Nicolson Ross Wier (NRW) method has been used to retrieve the material parameters from transmission and reflection coefficient. Upon incorporation, remarkable enhancement in parameters is observed whereby bandwidth increases by factor of 3.75, directivity increases by 5% and front to back lobe ratio improves by 31% with ESRR metamaterial.