Metasurface absorbers have shown significant potential in stealth applications due to their adaptability and capacity to reduce the backscattering of electromagnetic (EM) waves. Nevertheless, due to the materials used in the terahertz (THz) range, simultaneously achieving excellent stealth performance in ultrawideband remains an important and difficult challenge to overcome. In this study, an ultrawideband absorber is proposed based on indium tin oxide (ITO) and polyethylene-terephthalate (PET), with a structure thickness of only 0.16λ. ITO sheets are utilized to achieve broad-spectrum, optical transparency and flexibility of the metasurface. The results show that absorption higher than 90% can be achieved in the frequency band ranging from 1.75 to 5 THz under normal TE and TM polarizations, which covers a wide THz band. The structure is insensitive to polarization angles and exhibits 97% relative bandwidth above 90% efficiency up to an oblique incident angle of 60°. To further validate the efficiency of the absorption performance, the radar cross-section (RCS) reduction investigation was performed on both planar and conformal configurations. The findings show that under normal incidence EM waves, both flat and curved surfaces can achieve RCS reduction of over 10 dB, covering an extremely wide frequency range of 1.75 to 5 THz. The metasurface presented in this study exhibits significant potential for use in several THz applications, including flexible electronic devices and stealth aircraft windows.

Multifunctional integrated meta-devices are the demand of modern communication systems and are given a lot of attention nowadays. Most of the research has focused on either cross-polarization conversion (CPC) or linear-to-circular (LP–CP) conversion. However, simultaneously realizing multiple bands with good conversion efficiency remains crucial. This paper proposes a multiband and multifunctional dual reflective polarization converter surface capable of converting a linearly polarized (LP) wave into a circularly polarized (CP) wave, in frequency bands of 12.29–12.63 GHz, 16.08–24.16 GHz, 27.82–32.21 GHz, 33.75–38.74 GHz, and 39.70–39.79 GHz, with 3 dB axial ratio bandwidths of 2.7%, 40.15%, 14.6%, 13.76%, and 0.2%, respectively. Moreover, the converter is capable of achieving CPC with a polarization conversion ratio (PCR) that exceeds 95%, within the frequency ranges of 13.10–14.72 GHz, 25.43–26.00, 32.46–32.56 GHz, and 39.14–39.59 GHz. In addition, to identify the fundamental cause of the CPC and LP–CP conversion, a comprehensive theoretical investigation is provided. Furthermore, the surface current distribution patterns at different frequencies are investigated to analyze the conversion phenomena. A sample prototype consisting of 20 × 20 unit cells was fabricated and measured, verifying our design and the simulated results. The proposed structure has potential applications in satellite communications, radar, stealth technologies, and reflector antennas.

Modern and fast developments of wireless technologies have directed to a great demand for resources. It can be seen in the study that the range of existing spectrum is not used effectively, therefore the frequency band should be observed to ensure proper usage and to have the information of primary or licensed user is very much essential. In this research work uplink of LTE (Long-Term Evolution) is observed through MF (Matched Filter) spectrum sensing technique of CR (Cognitive Radio) network. This method examines the existence of signals in minimum possible time, reduces the hindrances between secondary users, increases accurateness of sensing and provides finest choice of threshold. In Uplink the System model which is used is known as SC-FDMA (Single Carrier Frequency Division Multiple Access). Entire simulation/results are prepared in MATLAB environment. This study also provides graphical contrast of simulated and theoretical results of matched filter and energy detection technique.

The basic stealth technology techniques are often limited to single frequency bands or single functionality, presenting a challenge for achieving superior stealth performance. In this study, an optically transparent coding metasurface (OTCMS) is designed based on glass and indium tin oxide (ITO) to realize dual-polarization conversion along with radar cross section (RCS) reduction at different frequencies. The fundamental unit, “meta-0,” consists of a diagonal I-shaped ITO resistive pattern that converts linearly polarized incident wave into its orthogonal component in two frequency bands (9.46–11.63 GHz and 15.86–17.28 GHz) with a fractional bandwidths of 21% and 9% respectively, whereas linear polarized incident wave is converted to circular polarized reflected wave in the 12.50–15.26 GHz band, with a fractional bandwidth of 20%. Next, the Pancharatnam–Berry (PB) phase is utilized to generate “meta-1” by simply rotating the “meta-0” with 90° to achieve a 180° phase difference between them. The “meta-0” and “meta-1” are arranged in an array using an optimized coding sequence to form OTCMS for RCS reduction. A reduction of more than 10 dB in RCS has been achieved across dual frequency bands for linearly polarized incident wave from 8.9–11.6 and 15.9–17.7 GHz. A prototype has been fabricated, and experimental outcomes align well with simulated results. This work opens avenues for the development of multifunctional and low-profile devices for applications in stealth jet windows, optical communication, microwave screening and beyond.