In this paper, the effect of a single-opening split-ring resonator (SRR) structure on the performance of ultra-wideband (UWB) microstrip patch antenna (MPA) is studied. Here a UWB MPA based on partial grounding is proposed, and the SRR structure is utilized to optimize other characteristics of the low-profile microstrip antenna while ensuring the bandwidth and gain remain unchanged. The proposed metamaterial structure, consisting of a 2×2 array of SRR, is loaded on the reverse side of the substrate. The volume of the proposed antenna is 61.6 mm×67.6 mm×1.5 mm. According to simulation and experimental results, the proposed microstrip antenna loaded with 2×2 SRRs performs better than that without SRR structure. It produces an operating band of 1.62-8 GHz while achieving circular polarization characteristics with an axial ratio (AR) bandwidth of 3.92-4.57 GHz. In addition, the performance of the proposed antenna is superior to relevant works of literature. The antenna can be widely utilized in wireless communication systems.