CPW Meander Line MIMO Antenna Loaded with Metallic Stubs to Enhance Isolation and Reduce Mutual Coupling

Abstract

A compact four-port MIMO antenna is proposed for the 2.4 GHz ISM band and wireless communication applications. The antenna occupies a compact footprint of 0.372λ0 × 0.372λ0 and is implemented on an FR4 substrate with a dielectric constant of εr = 4.4. Initial antenna design study for unidirectional radiation and high frequency band. Ultimately, a CPW antenna featuring with menderline is designed for unidirectional to lower frequency resonances. A coplanar waveguide (CPW) feeding scheme is employed, and inter-element isolation to enhanced through the antenna’s inherent self-isolation upto −24 dB and reduce mutual coupling. Further improved by integrating a strategically positioned parasitic element between the radiating elements, achieving a peak isolation of 27 dB. The design offers a measured peak gain of 2.83 dBi and a radiation efficiency of 96%. It covers an impedance bandwidth of 1.81–3.37 GHz with a minimum return loss of 49 dB. MIMO diversity analysis confirms an envelope correlation coefficient (ECC) below 0.01, a diversity gain (DG) of 9.99 dB, a channel capacity loss (CCL) of 0.36 bits/s/Hz, and a mean effective gain (MEG) less than −3 dB, all within standard performance limits. The fabricated prototype was experimentally validated through S-parameter, radiation pattern, and gain measurements, which exhibit good agreement with the corresponding simulated results, thereby validating the proposed antenna’s suitability for high-performance ISM-band wireless communication applications.