In this research, we present the reflective cross-polarization conversion metasurface operating in the X- and Ku band of microwave frequencies. The proposed polarization converting device comprises a cross-shaped meta-structure surrounded with a split ring resonator. We have numerically calculated and showed that the proposed metasurface manifests 90% PCR in the operating band from 8.5-16 GHz. It is noticed that the outer split ring resonator is the main contributor in enhancing the cross-component of the reflected wave, which rotates the incident wave into its orthogonal counterpart. Furthermore, it can also be scalable to other operating bands by carefully selecting the materials and optimizing the design parameters. This kind of reflective meta-device would be prudent for the applications of beam reflectors, antennas, and holography. Keywords metasurface, microwave frequency, polarization conversion, symmetry breaking I. INTRODUCTION After the primary effort by Landy et. al. in 2008 on single and narrow-band Gigahertz (GHz) perfect absorber, an enormous emphasis awakened of the optics and photonics researchers towards this stimulating area [1]. Thereafter, a variety of metasurface based EM and optical components has been realized including single, dual, triple, multi-band, wide-band, single- and multi- layer etc. ranging from the microwave-infrared range. In addition to meta-absorbers, polarization converters had also gained huge significance owning to their many applications in antennas, holograms, transmissive surfaces, beam splitters, wireless communication and imaging etc. Previously, polarization conversion phenomena can be obtained by using the conventional approaches of optical grating, dichroic crystals and birefringence effect etc. These methods limit the practicality in real applications due to the bulky weight, narrow bandwidth and costly fabrication process. In recent years, a new class of two dimensional (2D) surfaces also called metasurfaces have been broadly employed to model various microwave and optical components including sensors, antennas, waveguides, absorbers and polarization converters etc. These 2D planar surfaces are composed of man-made artificially fashioned meta-molecules possesses different rotation, shapes, size and materials etc. Through these metasurfaces, electromagnetic (EM) waves can be manipulated by altering their periodic elements and design parameters to achieve exotic and unusual features which cannot be realized with natural materials. Polarization conversion metasurfaces can be modeled in two different operation modes, reflection mode and transmission mode. In reflection mode, anisotropic resonators play a role to control the EM reflection of the incident waves and to rotate into its orthogonal component. A lot of research has also been conducted in anisotropic reflective metasurfaces to attain cross- and circular polarization conversion. In transmission mode, chiral structures are used to alter the transmission of incoming EM waves and to use them in achieving the polarization transformation. Similarly, people also implemented chiral metasurfaces in different configuration including single- and multi- layer etc. Most of the implemented devices rely on multi-layer and multi-faceted arrangements [2]. Advanced and modern communication systems demand highly efficient, broadband and single-layer polarization conversion metasurface. In this paper, authors’ motive to investigate highly efficient wideband metasurface which can transform the linearly polarized EM waves into its counter orthogonal component. Our reported meta-device converts the linearly polarized waves into its cross component over a broad spectrum of 8.5 to 16 GHz. The proposed metasurface operates in the reflection mode having efficiency of more than 90%. The designed configuration possesses three-layer scheme, i.e., top anisotropic metasurface, middle lossy dielectric spacer and bottom ground film. Furthermore, the proposed architecture can also be scalable to mm-wave and terahertz band. This kind of reflective meta-device would be prudent for the applications of antennas, imaging and beam generations. Fig. 1. Schematic of the proposed symmetry breaking metasurface along with its geometric characteristics, where P = 8 mm, R = 3.14 mm, W = 0.9 mm, G = 0.8 mm, W1 = W2 = 1.6 mm, L1 = 1.7 mm, L2 = 1.5 mm, S = 0.25 mm, td = 2 mm and tm = tg = 0.035 mm (a) front view and (b) prospective view II. DESIGN TECHNIQUE The meta-unit cell is composed of a + sign shaped patch antenna surrounded with a circular split-ring resonator. The design procedure, modeling and simulation are carried out by employing the frequency-domain EM tool CST studio [3, 4]. To export its electromagnetic features, as shown in Fig. 1. The proposed meta-design is analyzed by considering the easily available EM solver, CST-Studio, which uses unit-cell boundary excitations across the x-y direction and open along the z-axis. The linearly x-polarized electromagnetic wave (EM) is taken as an input source to excite the symmetry breaking polarizing metasurface. The reflected co- component along with cross-polarized reflection parameter are computed and depicted in Fig. 2. It has been observed in Fig. 2 that the cross-polarized parameter is approaching its maximum value for the operating frequency from 8.5 GHz to 16 GHz, whereas the co-polarized reflection component attains its minimum value (ref. Fig. 2). Fig.2. Simulated reflection features of the proposed symmetry breaking metasurface III. RESULT AND DISCUSSION When an EM wave falls on the top surface of the metamaterial, its overall absorption is determined from the following equation (1) Where, and are the transmitted and reflected energies of the designed metasurface. The subscript (xx) and (yx) depict the co- and cross components respectively. The transmitted energy demolishes due to the inclusion of thick metallic sheet at the bottom, so, the total absorption is mainly dependent on the reflection component of the proposed metasurface. The actual absorption of the designed metasurface is below 10% because the designed has a large cross-reflection component as depicted in Fig. 2. The actual absorption of the metasurface is below 10% from 8.5-16 GHz. 24681012141618-60-50-40-30-20-100ReflectionFrequency (GHz) rxx ryx The capability to convert the EM waves into its cross-polarizing can be measured in terms of its polarization conversion ratio (PCR), stated as. (2) Figure 3 demonstrates the converting efficiency of the proposed symmetry breaking metasurface as more than 90% across the large operating band (8.5-16 GHz). Therefore, the proposed symmetry breaking anisotropic device can be treated as a broadband polarization converter rather than a meta-absorber. Further, we can predict that the anisotropic structures can give us the polarization conversion features and they are very suitable for the implementation of polarization conversion metasurfaces in advanced systems. As it has a very large cross-component of reflection, so it gives a very poor absorption results. Fig. 3. Simulated conversion efficiency of the proposed symmetry breaking metasurface. In this section, we verify the reflective cross-polarization conversion metasurface working in the X and Ku band of microwave frequencies spectrum. We have numerically designed and revealed that the proposed metasurface displays 90% PCR in the operating microwave frequencies from 8.5-16 GHz. Furthermore, its geometry can also be ascendable to other operating frequencies band by carefully picking the materials and adjusting the design parameters. This kind of reflective meta-device would be prudent for the applications of beam reflectors, antennas, and holography. IV. CONCLUSION In summary, a highly efficient wideband linear reflective polarization rotator was investigated in this study. This meta-device possesses three-layer device configuration, top and bottom metallic layers and middle lossy dielectric spacer. The PCM illustrated more than 90% efficiency over a broad spectral range ranging from 8.5-16 GHz. Moreover, the proposed reflective meta-device can also be extended for other operating regimes, i.e., THz and IR, if we carefully chose the constitutive materials and geometric parameters.