An efficient multifunctional metasurface for cross and circular polarization conversion is presented in this letter. The metasurface acts not only as an efficient polarization converter for linearly polarized wave over frequency bands of 5.3–5.4, 7.2–8, and 12.3–13.76 GHz but also perfectly converts linearly polarized wave into circularly polarized wave over multiple bands of 5.1–5.2, 5.6–6.85, 8.8–11.2, and 14.9–20.2 GHz. The behavior of the metasurface is quite stable under oblique incidence for certain bands up to 75°. The broadband circular- polarization conversion, compactness, angular stability, and multiple functionality make it a strong candidate for many applications in the strategic C -, X -, Ku -, and K -bands.

Intelligent reflecting surfaces (IRS), also known as reconfigurable intelligent surfaces (RIS), have currently received much attention for their applications in wireless communication. The n-bit RISs presented in the literature are restricted to a single resonance and single polarization. These shortcomings create hurdles to engage more number of users and design a low-cost system (i.e., a separate hardware is required for each desired frequency band and each polarization). However, these issues can be solved if frequency reconfigurability and multiple polarization states (i.e., TE and TM) can be achieved in one structure. This paper presents a new multi-bit reconfigurable reflecting surface (RRS) with frequency-reconfigurable functionality working for both TE and TM polarized waves. The proposed design is tunable between 1.8-2.3 GHz and 2.95-3.9 GHz for TE and TM polarized electromagnetic (EM) waves, respectively. To simultaneously achieve the frequency reconfigurability and phase tailoring (varied from 0 ^$\circ$ to 315 ^$\circ$ ) in the proposed structure, the super-cell technique is used. This latter is incorporated in a phase gradient metasurface with different digital coding patterns to perform beam scanning and splitting functionalities. The simultaneous frequency reconfigurability and phase controlling for both TE and TM polarized waves, make this RRS a potential candidate for future RIS and reconfigurable devices.

In this letter, a novel bianisotropic omega frequency selective surface (FSS) is presented. The distinctive feature of the surface is that it offers simultaneous absorptive and partial reflective operation at seven frequency bands that range from the C-band to the K-Band. The maximum absorption (~ 99%) from one side is obtained at 14.312 GHz, while reflection from the other side remains between 75% and 99%. Moreover, the FSS provides the same behavior for any arbitrarily oriented linear polarized wave as well as circularly polarized waves. Furthermore, the surface is stable against oblique incidences of up to 60° at the lower frequency bands. The proposed FSS has potential applications in Fabry-Perot cavity antennas with reduced radar cross-section (RCS).

The purpose of this study was to characterize the alterations in microstructural organization of arterial tissue using higher-order diffusion magnetic resonance schemes. Three porcine carotid artery models namely; native, collagenase treated and decellularized, were used to estimate the contribution of collagen and smooth muscle cells (SMC) on diffusion signal attenuation using gaussian and non-gaussian schemes. The samples were imaged in a 7 T preclinical scanner. High spatial and angular resolution diffusion weighted images (DWIs) were acquired using two multi-shell (max b-value = 3000 s/mm²) acquisition protocols. The processed DWIs were fitted using monoexponential, stretched-exponential, kurtosis and bi-exponential schemes. Directionally variant and invariant microstructural parametric maps of the three artery models were obtained from the diffusion schemes. The parametric maps were used to assess the sensitivity of each diffusion scheme to collagen and SMC composition in arterial microstructural environment. The inter-model comparison showed significant differences across the considered models. The bi-exponential scheme based slow diffusion compartment (Ds) was highest in the absence of collagen, compared to native and decellularized microenvironments. In intra-model comparison, kurtosis along the radial direction was the highest. Overall, the results of this study demonstrate the efficacy of higher order dMRI schemes in mapping constituent specific alterations in arterial microstructure.

In this paper, a single-layer reconfigurable reflective metasurface is presented. The proposed metasurface operates at 5.4 GHz and can achieve either absorption or cross-polarization conversion corresponding at two different diode biasing states. The reflective metasurface acts as an absorber for an incident wave when the diodes are forward-biased. Similarly, it changes the polarization state of the reflected wave for a linearly polarized incident wave when the diodes are reverse-biased. The proposed structure maintains the aforementioned performance characteristics for oblique incidence, up to 60° compared to the perpendicular incidence. The proposed metasurface can achieve linear to linear polarization conversion with polarization conversion ratio (PCR) > 95% and absorption, with absorption ratio (AR) > 80% in the same frequency band just by reconfiguring the state of the PIN diodes.