Remotely Controlled Reconfigurable MIMO Antenna for Wireless Communication Applications

In this paper, a frequency-reconfigurable dual-element MIMO antenna is designed and developed. The antenna is implemented on the modified FR-4 substrate of size 30×50×1.6 mm³. Resonance and stimulus tuning under the sub-6 GHz working frequencies were also improved using the iterative design process in four phases. The first iteration added a second coupler but did not resonate due to the saturation of the ground plane. In later iterations, slot modifications, half-ground structures, parasitic loops, and Defected Ground Structures (DGS) were introduced with the objectives of achieving better impedance matching and overall frequency response. The result for the last version from a staircase ground plane with a T-shaped stub leaded to resonances at the following frequencies: 3.6, 3.9, 4.8, 5.9 and a broadband response among 6.15 and 6.5 GHz, with return losses from - 14 dB to - 33 dB. The proposed antenna features two PIN diodes for frequency reconfigurability and, therefore, has four operating modes. Depending on the states of the diodes, the antenna actively tunes its resonance frequencies to different bands from 3.72 GHz to 6.35 GHz with desirable return losses. All configurations of the antenna exhibit an omnidirectional radiation pattern with a 5 dBi average gain and an efficiency of 75% in broadside directions. These PIN diodes were wirelessly operated using the Node-MCU module, eliminating the manual tuning. Thus, the suggested MIMO antenna can be a good candidate for future wireless communication systems, which also include applications, such as 5G and sub-6 GHz.