## 1 Introduction  
Wireless sensor networks (WSNs) are used in wireless communication systems for various applications, such as smart cities, wireless monitoring, military surveillance, and medical imaging [1, 2, 3]. The polarization of an electromagnetic wave represents the direction of an oscillating electric field while traveling through any channel. Manipulation and control of the polarization state have many applications in wireless communication systems, such as satellite communication, remote sensing, and stealth technology [4]. In communication systems, the choice of antenna depends upon the applications and medium. In these systems, problems due to Faraday rotation, polarization mismatch, and multipath fading result in the degradation of the performance of channel. Therefore, circular polarized (CP) waves are used in these cases instead of linearly polarized (LP) waves; in particular, in communication systems and global navigation systems (GNSs). Obtaining CP waves in dual-wide-band for multiband operation is a challenging task. There are essentially two methods to obtain CP waves. The first is by employing CP antennas using the direct generation phenomenon. Dipoles and spiral and helical antennas are examples of such antennas [5, 6, 7]. The other method of obtaining CP waves is using a transformation method for the polarization state: so-called polarization conversion. CP antennas based on the generation phenomenon contain large and bulky elements, which are usually cascaded with built-in polarizers [8], making these antennas complex structures. Furthermore, CP antennas, once fabricated, cannot be used as other types of antennas. In contrast, obtaining CP waves using the polarization conversion method allows antennas to perform both as LP and CP antennas. If required, an LP antenna with linearly polarized characteristics alone can be used, and when CP wave characteristics are required, an LPantenna along with a polarization converter can be used. Furthermore, LP antennas are simpler to design. Conventional polarization converters (polarizers) are bulky and often have narrow operational bandwidths. These converters usually consist of birefringence wave-plates and liquid crystals [9; 10; 11; 12], which are quite complex. To simplify and miniaturize the polarizers, the concept of polarization conversion has been developed using frequency-selective surfaces [13; 14; 15], metamaterials [16; 17], and metasurfaces [18; 19]. These polarizers have also been developed based on a reflection mode, which causes feed blockages [20]. Therefore, polarizers operating in transmission mode are desired. Existing transmissive polarizers are based on a single wide-band of operations [21; 22]. In satellite communication systems with non-adjacent transmit and receive channels lying at two distinct bands, dual-band polarization conversion can play an important role. Further, the need for an orthogonal polarization direction with high isolation between the transmit and receive signals requires an orthomode transducer (OMT), which makes the system bulky. A dual-band, dual-polarized converter may be an ideal candidate for such applications, removing the need for an OMT and making the system less complex. Furthermore, a dual-band polarization conversion operation is required for the merging of multiple systems to achieve adequate volume and size reductions. Thus, in the last couple of years, researchers have worked on dual-band polarizers [23; 24; 25; 26; 27; 28; 29; 30; 31] using multi-layered [24; 29; 31], bi-metallic layered [23; 25; 26; 28; 30], and single-layered structures [27]. Different periodic-structure unit cell elements have been used for dual-band polarizers. [PERSON] et al. [28] proposed dual-band polarization converters using JC-based structures. The structures were bi-layered and dual-band performance with 24% and 11% bandwidths was achieved. [PERSON] et al. [31] reported a polarization converter in X and Ku bands using double split-ring layers with a central rectangular patch.