A dual-element miniaturized multiple-input-multiple-output (MIMO) antenna with a defected ground plane and a tapered microstrip feed line is introduced in this article. It achieves a bandwidth (BW) of 10.8 GHz (7.2-18 GHz), frequency ratio (FR) of 2.5, and average isolation of 15 dB over the entire operating band. The proposed antenna is right hand circularly polarized (RHCP) and achieves an axial ratio of < 3 dB in the frequency band ranging from 7.2 to 8.9 GHz. The performance characteristics of the proposed antenna are analyzed in terms of the envelope correlation coefficient (ECC), mean effective gain (MEG), total active reflection coefficient (TARC), isolation between the ports, and channel capacity loss (CCL), and the values obtained are 0.1607, 9.99 dB, ±3 dB, -11 dB, -7 dB, 0.20 bits/sec/Hz respectively. The proposed MIMO antenna is fabricated on an FR-4 dielectric substrate of dimension 10.6×10.3×1.6 mm3 and has good agreement between simulated and experimental results. The proposed antenna can be used for C, X, and Ku band applications.