Contents I. Introduction
For multi-band applications, mobile communication systems need to have a large band width [1]–[2]. In order to fulfill the demand, Technology from SISO to SIMO to MISO to MIMO wireless communication systems have advanced [1]–[4]. A high need for data transmission rate, high reliability, and channel capacity increase are also necessary. The MIMO technology has been studied [5]. This technology requires the use of multiple transmitters and multiple receivers to send and receive the data also for improving the high data rates and channel capacity [5]–[6]. Although the MIMO system likewise enhances the single element performance into multiple element performance, the micro strip patch antenna has its own benefits, including simplicity of fabrication, compactness, and ease of integration with wireless devices [7]–[8]. Integration of many antennas is utilized in conjunction with low mutual coupling and reduced multi path fading to increase the MIMO technology's performance [9]–[10]. Since November 2017 [11], China has allotted the sub-6GHz frequency bands (3.4-3.6 GHz and 4.8-5 GHz) for 5th generation mobile communications. Since each antenna in a MIMO system must function independently in order to guarantee the MIMO system's functionality, isolation and ECC (envelop correlation coefficient) of two or more antennas play a critical role in MIMO systems [12]. To achieve improved isolation between the producing elements (Antennas) during antenna design is the main challenge in MIMO systems, according to [13]–[14]. In the recently reviewed literature for isolation, a variety of decoupling procedures are used [16]. They consist of a flawed ground substrate, a split ring resonator, a parasitic strip, and others [15]. A select number of the literary works reported in [17] are relevant to various wireless applications. Less research has been done on MIMO antennas for X-band (8–12 GHz), Ku band (12–18 GHz), and K band applications (18 to 27 GHz). MIMO wireless communications use multiple antennas at both the originator (transmitter) and final location (receiver) [18]. By letting data to pass through several signal paths at once, the antennas at each end of the communications circuit are merged to reduce mistakes, increase data speed, and increase radio transmission capacity [19].
