IMPS College of Engineering and Technology (or Impscet) is an engineering and management college located in Malda, West Bengal, India. The college was established in 2003. It provides engineering, technological and management education. The college is an AICTE-approved institution and is affiliated to the West Bengal University of Technology.
Metamaterial absorbers (MMA) have emerged as viable options for electromagnetic wave manipulation owing to their compact design, tunability, and high absorption efficiency. This work presents the design and analysis of a switchable MMA that incorporates vanadium dioxide (VO2) to achieve thermally tunable absorption characteristics. The structure consists of a polyimide layer serving as the dielectric substrate, a gold-based ground plane, and a top surface of VO2. This designed MMA produces a 9.7 THz bandwidth by keeping absorption levels over 92% in the 4.5-14.2 THz band with a fractional bandwidth (FBW) of 103.74%. The absorption peak consistently rises from 2% to 99.3% with changes in conductivity of VO2 from 200 to 2 & times; 105 S/m. This changeover allows thermal tunability between highly reflecting and extremely absorbent phases. In order to analyze the absorption response of the proposed MMA, many dielectric layers are considered, including polyimide, lossy silicon, Al2O3, Quartz lossy, and SiO2. Additionally, the absorption response of the MMA is also evaluated using various conductive materials (aluminium, gold, copper, iron) apart from VO2. An analysis on the effects of incidence and polarization angles on absorbance in TE and TM modes is performed in order to confirm the polarization insensitivity of the designed MMA. The suggested MMA has a wide range of possible terahertz-based uses, including biosensing, medical imaging, cloaking, EMC and optical switches.
We report a SIW-based Terahertz (THz) array antenna that integrates graphene filters, photonic bandgap (PBG) structures, and a power splitter circuit. The intended design is simulated on a 10-mu m-thick fused quartz substrate, and both the ground and patch layers are made using gold with a thickness of 0.6 mu m. The proposed SIW array antenna exhibits multi-band resonances at 0.042 THz, 0.0842 THz, 0.19 THz, 0.306 THz, 0.616 THz, and 0.754 THz, achieving impressive reflection coefficients (S11) lower than -27 dB across all bands. The corresponding gain values are 10.1 dBi, 10.3 dBi, 10.9 dBi, 11.1 dBi, 11.5 dBi, and 11.7 dBi, respectively. The maximum radiation efficiency achieved by the design is reported to be 80 %. At the lowest operating frequency, the electrical size of the recommended structure is 0.3063 lambda x 0.14 lambda. To enhance performance, a graphene-loaded filter is integrated between the antenna and the power divider, which improves return loss characteristics, and the maximum gain reaches 11.7 dBi at 0.754 THz. The addition of the graphene filter also effectively suppresses unwanted harmonic frequencies generated within the antenna structure. The proposed design is highly suitable for advanced applications in the THz spectrum, including sixth-generation (6G) satellite communication systems and future-generation mobile phones.
This study introduces a reconfigurable and switchable terahertz metamaterial absorber (MMA) based on vanadium dioxide (VO2), exploiting its thermally induced phase-transition properties. The geometry of the proposed MMA is configured using three-layered Metal-Insulator-Metal (MIM) topology, by implying VO2-based metal layer of closed hexagonal ring resonators (CHRRs) on the top surface, then an insulating middle layer of paper substrate, and a perfect conducting bottom surface of gold. The phase transition of VO2 enables dynamic tunability and switching of the absorber in the terahertz regime. The designed MMA achieves near-perfect absorption of 99.99% at 4.667 THz with a bandwidth of 0.204 THz (4.601-4.805 THz). The resonance frequency shifts with variations in the surrounding refractive index, yielding sensitivities ranging from 0.195 to 0.255 THz/ RIU. Owing to this sensitivity, the absorber can distinguish six types of human cancer cells, including breast, cervical, blood, tongue, adrenal gland, and skin cancers. Furthermore, machine learning (ML) techniques are employed to optimize absorber parameters and predict reflection and absorption characteristics with high accuracy, which is validated using regression metrics. These results demonstrate the potential of the proposed VO2-based MMA for terahertz biomedical sensing and cancer detection applications.
A novel triple-band THz metamaterial heat absorber based on symmetrical circular and rectangular stubbed resonators (SCRL-SR) is proposed for high-sensitivity dielectric characterization. The design employs VO2-based resonators on a polyimide substrate within a compact unit cell of 9.6 mu m & times; 9.6 mu m. It exhibits three distinct absorption bands at 21.24 THz, 23.61 THz, and 25.59 THz with near-perfect absorptions of 99.99%, 99.20%, and 99.88%, respectively. The electromagnetic response is validated using Mode Coupling Theory (MCT) and Transmission Line Model (TLM), showing strong agreement with finite element method (FEM)-based simulations. The absorber maintains polarization independence and stable performance for incidence angles up to 90 degrees (TE) and 60 degrees (TM). Dynamic tunability is achieved through the thermally induced insulator-to-metal phase transition of VO2 near 340 K, modeled using temperature-dependent conductivity and permittivity. This transition introduces switching behavior governed by heat conduction across the VO2 substrate interface and external thermal excitation resulting in modulation of resonant peak absorption. Thermal diffusion within the thin film further influences the transition dynamics. In addition, mass transfer effects such as gas absorption and analyte interaction modify the local refractive index, enhancing sensing performance. The sensor demonstrates high refractive index sensitivity, with responsivities of 1.725 THz/RIU, 0.4125 THz/RIU, and 0.6375 THz/RIU, along with quality factors of 15.39, 71.54, and 50.17. These combined electromagnetic, thermal, and physicochemical interactions establish the SCRL-SR absorber as an efficient and highly responsive THz sensing platform that can be used for gas spectroscopy, chemical detection, biomedical diagnostics, and environmental monitoring.
This article presents a compact UWB monopole antenna based on a decagonal ring, in which a set of fractal-inspired slots is introduced to broaden the operating bandwidth while maintaining a compact structure. These slots are added primarily to increase the electrical path without increasing the overall radiator size, thereby making the antenna easy to integrate when space is limited. A prototype is fabricated on a standard FR4 substrate with dimensions of 40 & times; 30 & times; 1.6 mm3. The proposed design is first optimized using full-wave simulations and then experimentally tested. The antenna operates continuously from 2 GHz up to 11.20 GHz, with a peak gain of about 5.5 dBi and a radiation efficiency close to 95.6%. Simulated and measured results show a satisfactory agreement over the whole operating range. Besides the wide frequency span, the antenna also maintains stable radiation patterns and satisfactory time-domain behavior, often challenging to obtain in compact UWB designs. Its compact footprint and simple fabrication make easy integration into different wireless systems. Owing to its compact, optimized design, wideband performance, excellent time and frequency domain characteristics, low cost, and ease of fabrication, the proposed antenna can therefore be used in IoT nodes, low-power wireless connections, Wi-MAX system, and several UWB sensing scenarios operating in Sub-6 GHz, C-band, and parts of the lower X-band spectrum.
