An Aperture-Shared High-Isolated MIMO Antenna Design Using Quarter-Wavelength Monopole as Differential-Mode Antenna

An aperture-shared high-isolated MIMO antenna design is proposed in this letter for mobile terminals. A 1/4 λ monopole antenna is utilized as the differential-mode antenna to avoid using the complex balanced-feeding structures, while a 1/2 λ loop antenna is adopted as the common-mode one. Different from the existing differential-common modes MIMO antenna designs, the differential-mode antenna in the proposed design is of 1/4 λ, and the geometrical asymmetry is exploited to compensate for the current asymmetry. Moreover, lumped elements are loaded at the end of antennas to miniaturize the antenna size, and a transmission-line model is presented to analyze the miniaturization principle. For validation, a self-decoupled MIMO antenna design working from 3.4 to 3.6 GHz is presented using the proposed scheme. Results show that the isolation between the antenna pair is better than 21.7 dB, and the envelope correlation coefficient (ECC) is lower than 0.002 across the working band with only a 0.1 λ₀ size.