converters have relatively narrow bandwidths [25; 26]. Recently, some all-metal phase-shifting structures have been proposed; these structures are either single-frequency or polarization-dependent structures. Some structures can only support waves that are either linearly or circularly polarized, due to a very limited bandwidth. However, because of the limitations of a substrate-less design, it is more difficult to simultaneously offer a set of desirable characteristics via an all-metal structure. An all-metal wideband phase-correcting structure (AWPCS), without these limitations, is generated based on the relative phase error obtained from post-processing actual near-field distributions of any EM sources [27]. However, researchers are trying to design broadband and single-layer cross-polarizers. In [28], the authors present a lightweight reflective polarizer constructed in an oval-shaped design that enables wideband CPC in the 10.2-20.5 GHz frequency range. Several effective and wideband cross-converters using a single layer have been described, including a slotted semicircle [29], a square-split-ring metasurface [30], a W-shaped metasurface [31], and a T-shaped metasurface [32]. Nevertheless, these structures only support CPC as a single operation.  
In addition, many researchers have focused on different metasurfaces to integrate many functionalities into a single structure. A polygon-shaped linear-to-circular (LP-CP) converter, with a 46% axial ratio (AR) bandwidth from 7.62 to 12.16 GHz, was recently proposed by [PERSON] et al., using anisotropic impedance surfaces in reflection mode [33]. This converter is capable of achieving both left- and right-handed circular polarization. A reflection-based single-layered multiband polarization converter in the K and Ka bands was proposed by [PERSON] et al. [34]. The structure was based on a hexagonal-shaped metal patch enclosed in a hexagonal ring, with a diagonal split only in the ring. It acts as a linear-to-circular polarization converter in dual bands, from 16.23 to 16.75 GHz and 48.6 to 48.8 GHz. The study in [35] describes a reflective multiband converter achieving maximum CPC at 13, 16, and 18 GHz. In [36], a novel polarization-twisting antenna configuration is presented that uses a linear polarization conversion metasurface to transform the radiated LP wave into an \(x\)-polarized wave. In low- and high-frequency bands, the dual linear-to-circular polarization converter can change the \(x\)-polarization wave into a left-handed circularly polarized (LHCP) wave and a right-handed circularly polarized (RHCP) wave. The limitations are that the composite structure is quite complex, large in size, and has a narrow bandwidth. A low-profile, multifunctional metasurface converter that is small in size and has both CPC and LP-CP functions is described in [37]. However, the additional air layer and the consequences of angular tolerance are not addressed. Because the designs mentioned above are unable to meet the conditions of multifunctionality and integration needed for the large-scale communication systems in use today [38], the application of polarization converters is severely limited. Today, the focus of researchers is on creating polarization converters that have multiple functions, are small in size, and have a larger bandwidth.  
In light of the above limitations of polarization converters, a new single-layer reflective multiband polarization converter for LP-CP and CPC is proposed in this paper. LP-CP conversion is realized across five distinct frequency bands, with incident vertical polarization by the metasurface converter. On the other hand, CPC is achieved across four frequency bands. To better comprehend the physical insights on the reflective metasurface and to investigate its performance, analysis of the surface current distributions has been carried out. Despite its simplicity, our design has potential applications in polarization manipulation, including antenna design and wireless communications.