Isolation enhanced compact dual-band quad-element MIMO antenna with simple parasitic decoupling elements

Abstract

In this work, a simple parasitic decoupling structure integrated compact dual-band quad-element Multiple-Input Multiple-Output (MIMO) configuration with improved isolation is proposed for 3.5 and 5.8 GHz bands of Worldwide Interoperability for Microwave Access (WiMAX) and Wireless Local Area Network (WLAN) applications. The lower and higher frequency bands accomplish an impedance bandwidth of 400 MHz (3.35 – 3.75 GHz) and 450 MHz (5.6 – 6.05 GHz), respectively. A slot integrated curve-shaped compact (11 × 20 mm2) dual-band monopole antenna is explored to implement the proposed compact MIMO configuration. A parasitic decoupling structure comprising T and inverted L-shaped thin metal strips is introduced between the orthogonally placed antenna elements. It exhibits dual stopband characteristics to enhance the isolation significantly at the targeted frequency bands despite the compact footprint (34 × 34 mm2) of the MIMO geometry.The optimized decoupling structure improves the isolation between the elements by 31.5 and 32 dB in the lower and higher bands than the MIMO geometry without decoupling elements. The antenna provides good radiation characteristics with peak gains of 4.18 and 3.62 dBi within the bands. The computed diversity metrics, such as envelope correlation coefficient (< 0.01), diversity gain (> 9.93 dB), mean effective gain ratio (-0.13 to 0.16 dB), channel capacity loss (< 0.4 b/s/Hz), and total active reflection coefficient (< -10 dB), ensures good diversity performance. The fair agreement between the simulated results using HFSS EM solver and the measured results on the fabricated prototype validated the proposed MIMO configuration.