A 3 × 3 mMIMO DRA Subarray for 5G IoT Applications With Reduced Number of Elements

The emergence of 5G and beyond 5G (B5G) technologies has paved the way for the interconnectivity of devices in the form of Internet of Things (IoT). This results in the transfer of huge amounts of data and requires systems (particularly antennas) capable of handling high-data rates and exhibiting large-channel capacity, high gain, and beam steerability to enhance the signal-to-noise ratio (SNR). However, many studies on antenna designs for 5G and IoT applications target some of the above properties and fail to incorporate all of them in a single design. This work proposes a massive multiple-input–multiple-output (mMIMO) subarray formed by a linear combination of four dielectric resonator antennas (DRAs) in a $1\times 4$ linear array. The DRA array is fed by three separate unequal corporate power dividers [to reduce the side lobe level (SLL)], resulting in a $3\times 3$ multiple-input–multiple-output (MIMO) array offering a three-fold increase in channel capacity as compared to the single port array. The proposed subarray can generate three high-gain beams independently steerable in the desired directions. The proposed array operates in the lower sub-6 GHz band with a measured impedance bandwidth of 900 MHz (3.0 GHz to 3.9 GHz). The three ports, P1, P2, and P3, provide a measured maximum gain of 8.2, 7.8, and 6.8 dBi, with -18 dB of SLL. The measured interport isolation is better than 15 dB for all the ports resulting in the achievement of the envelope correlation coefficient lower than 0.15 and diversity gain (DG) greater than 9.5 dB in the band of interest. Additionally, the link budget analysis confirmed that the proposed mMIMO subarray can establish a reliable link up to 230 m, 260 m, and 175 m for ports P1, P2, and P3, respectively, with an input power of 21 dBm. To the best of the author’s knowledge, this is the first mMIMO subarray that has a $1\times 4$ linear array arrangement and is fed by three independent ports, resulting in a $3\times 3$ mMIMO subarray, suitable for the base stations, femtocell, and indoor access points applications in 5G and IoT scenarios.