# Eight Element Wideband Antenna with Improved Isolation for 5G Mid Band Applications
## 1 Introduction  
The Sub-6 GHz 5G technology has become a critical component in 5G deployment due to several merits other than the higher frequency (mm-Wave), like wider coverage in rural areas, lower power consumption, higher penetration, higher data rate, and mobility [1, 2]. The growing demand for such a high data rate communication system seeks a technology where multiple antennas are utilized at the transmitter as well as receiver to enhance the channel capacity of the communication link without increasing the transmission power channel the bandwidth [3, 4, 5]. MIMO technology continues to serve as the foundation for 5G wireless communication networks. In addition to the multipath characteristics of the communication channels, the performance of such a system relies on the meticulous design of the MIMO systems. Nowadays, low-profile wideband antennas are gaining popularity due to their ease of fabrication and cost-effectiveness as well as compact sizes. In this context, the design of flexible antennas needs greater attention, especially in compactdevices with space constraints where the antennas are placed closer to each other leading to strong mutual coupling between them. The extensive coupling between the inter-elements leads to low efficiency. In MIMO systems, successful communication requires isolation among elements of more than 12 dB [5]. There have been several methodologies implemented recently to reduce the coupling and thereby increase the isolation like the use of parasitic elements [6], defective ground structures [7], stubs [8], self-isolating decoupling structures [9; 10], lozenge structures [11], artificial intelligence approaches [12] and so on. In recent years, numerous flexible antennas using two ports [8; 13; 14] and four ports [11; 15; 16] have been modeled for the 5G mid-band. In [8], a compact and more isolated dual-port antenna is presented. The antenna offers good impedance matching and satisfactory omnidirectional patterns with co-cross coupling, but the bandwidth is low. A wideband wearable antenna with a neutralization line (NL) between the radiators is presented in [14]. The NL provides remarkable isolation of 32 dB for the working bands. However, the antenna is vulnerable to antenna performance degradation due to the use of textile substrates prone to absorbing moisture. A transparent and flexible two-element antenna that utilizes the wired metallic mesh is proposed in [13] for 5G internet-of-things (IoT) applications. The antenna is compact, but the gain and efficiency of the antenna are low. In [11], a four-port multiband antenna with a modified decagon substrate is examined for wireless applications. The antenna provides satisfactory gain and multiband operation. Another quad-element antenna is proposed in [16]. In the primary planes (E and H), the antenna displays good omnidirectional and bidirectional patterns, respectively. The antenna bandwidth and efficiency are good and are appropriate for the intended applications. However, the number of users that [11; 16] can support is still quite small. An increase in the number of ports can accommodate more users with enhanced channel capacity as well as higher data rates [17]. In this regard, researchers have been focusing on the development of several eight-element antennas for various 5G applications [1; 18; 19; 20; 21; 22; 23; 24]. However, all the above-specified literature lacks antenna flexibility and therefore the development of a flexible eight-element antenna for 5G mid-band needs attention. Recently, a flexible eight-element antenna for this specific band has been designed on a flexible polyimide substrate [2]. The antenna has good radiation properties and a small footprint. However, the antenna's low simulated bandwidth and gain limits its use in real-time MIMO applications.