Stacked frequency reconfigurable Yagi‐like MIMO antenna system

Abstract

In this work, a 2‐layer frequency reconfigurable Yagi‐like multiple‐input–multiple‐output (MIMO) antenna system is proposed based on a closed pentagonal slot‐loop excitation. The MIMO system consists of 4 identical active antenna elements reactively loaded with varactor diodes to achieve frequency reconfigurability over a band from 1.5 to 2.1 GHz. The distinguishing feature of the proposed work is achieving Yagi‐like directional characteristics over a very wide frequency band. The conventional omni‐directional pattern of a slot antenna is made directional by using a parasitic metallic reflector layer below the substrate. By using the reflector element, the back‐lobe radiation is highly suppressed and a front‐to‐back ratio of 5–13 dB is achieved within the entire frequency band of operation. The proposed design is compact with an overall size of 100×100×20thinmathspacenormalmm3, and a reflector size of 110×110thinmathspacenormalmm2. A single element has a maximum peak gain of 4 dBi and total measured radiation efficiency of 76%. The antenna system also shows good MIMO performance with high port isolation of 11.3 dB and very low envelope correlation coefficient values within the operational band.

Frequency Reconfigurable Quad-Element MIMO Antenna with Improved Isolation for 5G Systems

“…However, these antenna configurations demonstrated a lower level of inter-element isolation and fixed-band operation. Dual-port MIMO antennas with frequency diversity were investigated in [26][27][28][29][30][31][32]. In ref.…”

“…In ref. [31], a Yagi-Uda antenna integrated with a varactor diode was investigated. But, the double-layer fabrication adds complexity and limits the practical applications of the presented antenna.…”

“…[34,35], four-element MIMO antennas with frequency diversity were designed, where varactor diodes and RF MEMS were implanted in SRR and rectangular slots for frequency diversity. However, the above-reported [29][30][31][32][33][34][35] antenna configurations required more substrate volume, a greater number of active elements/switches, which complicates antenna design, and high interelement coupling. Poor isolation implies that adjacent resonators are correlated, resulting in poor antenna performance.…”

Graphene based Adaptable Frequency Stack Antenna with Common Ground for Cognitive Radio Application

“…Aperture coupled stack antenna with PIN Diodes is presented in [13], where the biasing of the diodes on the feed network were changed for frequency switching. Stacking with varactor diode is used for frequency recon gurable MIMO antenna [14]. Stacking with mechanical rotation for frequency switching was discussed in [15], where the upper layer is rotated for frequency recon guration.…”