# Pentaband Dual-Polarized Antenna for Multiservice Wireless Applications
## 1 Introduction
In another design, a square-ring slot radiator was used to develop a triple-band antenna for 4G and 5G mobile terminals, achieving 16 dB isolation [25]. Similarly, an asymmetric co-planar strip G-shaped structure was proposed for another triple-band antenna with 18 dB isolation [27]. Additionally, a four-element antenna for quad-band applications that used meander-line-based radiators exhibited more than 22 dB isolation [28]. Another approach involves the use of decoupling networks to improve isolation between antenna elements. For example, a six-element four-band MIMO antenna was proposed for IoT/WLAN/Sub-6 GHz/X-band applications, utilizing a decoupling network [29]. However, this design achieved a low level of isolation. It is important to note that all the approaches mentioned above employed linear polarization (LP). Recently, circular polarization (CP) has gained attention as a promising technique to enhance the performance of MIMO antennas in wireless communications. CP MIMO antennas have been reported to offer advantages such as reduced fading and better channel capacity compared to LP MIMO antennas [30]. Therefore, developing CP MIMO antennas with high isolation is a promising avenue for future research. Several CP MIMO antennas have been proposed in the literature, including dual circular polarization [31; 32]. However, there are only a few research papers that demonstrate simultaneous LP and CP in single multiband MIMO antennas [33; 34; 35]. Dual-polarization antennas enable multiband operations with high isolation between nearly radiating bands, leading to better reception. For instance, a tri-band MIMO antenna was proposed to cover the LP GSM band, WLAN band, and WiMAX band with CP [33]. In another triple-band MIMO design, the first two bands use LP, and the third band uses CP [34]. Furthermore, a meander-line pentaband MIMO antenna with circular polarization was proposed for mobile satellite services and internet-of-things applications [35]. However, despite these advancements, there is still a need to provide dual polarization that covers other frequency bands. This can be achieved through further research and development of CP MIMO antennas with high isolation, which will lead to better performance in wireless communication systems [33; 34; 35]. In the search for high-performing antennas for wireless communication applications, a new design has emerged that offers both circular polarization and multiband capabilities. The proposed design presented in this study offers a simple yet effective solution to achieving pentaband coverage with dual circular polarization. The design uses a rectangular patch with an asymmetric edge slot, truncated to create a triple band, and an annular ring slot with stepped apertures of different sizes to achieve pentaband coverage. This design is a significant improvement over previous designs that have only demonstrated either LP or CP in single- or dual-band MIMO antennas. For instance, the proposed design covers navigation, WLAN, and fixed/mobile satellite communication applications with a slight deviation in the resonance frequency without disrupting the bands. Moreover, the proposed design is also extended to quad-port MIMO, where a ground slit is incorporated to achieve over 20 dB of isolation. The diversity parameters of the proposed dual-polarized antenna design, such as the envelope correlation coefficient (ECC) and diversity gain (DG), show that the design is well-suited for MIMO applications. A comparison of the proposed design with existing cited references is provided in Table 1.  
The table compares various dual-polarized antennas with the proposed design in terms of dimensions, operating bands, number of ports, polarization, and isolation. The antennas in the table operate with dual-, triple-, quad-, and pentaband coverages and have LP or CP polarizations. The proposed design is a pentaband dual-polarized antenna with 4 ports and achieves an isolation of 21 dB. The dimensions of the proposed antenna are 62 \(\times\) 62 \(\times\) 1.6 mm\({}^{3}\).