# Designed Circularly Polarized Two-Port Microstrip MIMO Antenna for WLAN Applications
## 1 Introduction  
In current communication systems, multiple-input multiple-output (MIMO) antennas are used to send and receive multiple data signals over the same radio channel [1]. MIMO antennas are important components in current wireless communication systems as they can reduce interference, and enhance connection quality and channel capacity without requiring more bandwidth. Electromagnetic wave interactions between near elements, which impact antenna parameters, such as bandwidth and radiation pattern, are a major challenge in MIMO antenna design [2, 3]. There are multiple antennas in base stations and devices. A sufficient distance between nearby patches is required to reduce mutual coupling [4]. To solve this problem, several methods have been explored to reduce mutual coupling, such as an electromagnetic band gap (EBG) structure [5, 6, 7], defected ground structure (DGS) [8, 9], neutralization lines [10], stub loading technique [11], slots [12], meta-material [13], and resonator structures [14]. A wide-band two-port circularly polarized MIMO printed antenna is obtained by designing the ground plane and employing asymmetric Z-shaped radiating patches to improve isolation [15]. To attain good MIMO properties, these approaches are frequently coupled. Antennas are used in a variety of wireless communications applications, including the short-range wireless local area network (WLAN) application [16]. WLAN MIMO systems are of interest to scientists that use them to increase wireless communications between electronic devices (such as PCs, laptops, and smartphones) [17]. WLAN systems use base stations or access points to deliver connectivity to wireless devices [18; 19]. In [20], the authors present a design of a leaky-wave antenna (LWA) array capable of generating six simultaneously-scanned directive beams when connected to a MU MIMO 802.11 ax base station Router WiFi for indoor smart wireless access point applications. In [21], the authors proposed a new full-rate coding scheme for MIMO-OFDM systems operating over slow-fading wireless channels. The scheme consisted of a block code sent over transmit antennas, OFDM tones, and radiation states of reconfigurable antennas. The transmit or receive antenna radiation patterns can be dynamically changed to improve system performance in a dynamic radiation pattern diversity (DRPD) MIMO system [22]. Several MIMO antenna systems for WLAN applications have been presented in recent years, with much of the research focusing on ways to reduce the mutual coupling result and to attain high isolation among antenna units because lesser dimensions and areas are limited when organizing antennas. However, some MIMO antennas are designed for the WLAN band (2.4/5.8 GHz) [23; 24; 25; 26]. Polarization and pattern diversity, on the other hand, appear to be promising techniques for decreasing the correlation between antenna far-fields without increasing the circuit dimension. Reduced signal attenuation, multi-path fading, and absorption losses are advantages of circularly polarized (CP) antennas [27; 28]. When compared to LP antennas, the CP MIMO antenna, extends wireless coverage, minimizes the polarization mismatch effect, and distributes power uniformly between feed points [29]. In terms of improving diversity gain (DG) or channel capacity (CC), CP antennas have been investigated as viable candidates for MIMO applications. Truncated corner metallic radiators are used along with periodic parasitic elements to make the CP MIMO antenna, to improve the isolation and axial ratio [30]. The antenna was designed with truncated corner square patches, and the parasitic element technique was also used for BW enhancement. The MIMO antenna in [31] was formed by two diagonally slotted square patches and four parasitic elements for performance improvement. The MIMO antenna attained good isolation of more than 18 dB while fitting on a board measuring 30 \(\times\) 30 \(\times\) 1.6 mm.