• B S SREEJA

      Articles written in Pramana – Journal of Physics

    • Design of polarisation-dependent multiband terahertz frequency-selective surface using two resonators

      S SASI PRINCY B S SREEJA E MANIKANDAN MANIKANDAN

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      The aim of this paper is to present the frequency-selective surface (FSS) filter operating in the terahertz regime, emphasising on its polarisation-dependent nature. The FSS filter consists of two-concentric hexagonal-shaped metal strips embossed on a gold layer over the teflon substrate, created in the form of a split ring resonator (SRR). The emphasised polarisation-dependent nature of the FSS structure has been proved by analysing the frequency response. Numerical simulation has been done using the CST microwave studio software. Resonance occurs at five frequencies in the transverse electric (TE) mode and at four frequencies in the transverse magnetic (TM) mode, describing the polarisation-dependent nature of the proposed FSS filter structure.

    • Dynamic frequency analysis of stress–strain-dependent reversibly deformable broadband RF antenna over unevenly made elastomeric substrate

      S DEEPA NIVETHIKA B S SREEJA E MANIKANDAN S RADHA M SENTHILPANDIAN

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      This paper presents the design and development of stretchable and deformable broadband antenna using low-cost silicone rubber-based dielectric substrate. A slot is introduced in the substrate to improve the stretchable behaviour. The dielectric properties of the substrate are measured using suspended ring resonator method. The proposed antenna uses silver elastomeric Lycra fabric as the conductive medium. The resistivity of the conducting Ag fabric is 1 $\Omega$ per sq. mm. The conducting patch and ground plane are attached with the substrate using silicone-based adhesive. The fabricated antenna is tested for its resonant characteristics using the vector network analyser.

    • Terahertz broadband metamaterial absorber enabled by SiO$_{2}$, polyimide and PET dielectric substrates

      A ELAKKIYA S RADHA B S SREEJA E MANIKANDAN

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      A broadband polarisation-insensitive terahertz (THz) metamaterial absorber (MMA) is presented in this paper. The MMA consists of a simple planar structure as a unit cell and an optically transparent indium tin oxide (ITO) ground plane, both are separated by a 50 $\mu$m dielectric substrate. We designed three combinations of MMA here, which are ITO–polyimide–ITO, ITO–polyethylene terephthalate (PET)–ITO and ITO–silicon dioxide (SiO$_{2}$)–ITO for the same planar structure. By changing the substrate of the structure, the resonant frequency and bandwidth of the absorber structure can be varied. The numerical simulation of the absorber shows that the absorptivity is $>$ 96% for all three substrates. Polyimide, PET and SiO$_{2}$ based absorbers demonstrated the bandwidth of 0.558 THz,0.603 THz and 0.658 THz with covered broadband frequency range of 0.4254–0.9829 THz, 0.457–1.16 THz and 0.511–1.169 THz respectively. ITO–PET–ITO absorber structure produced optical transparency. These bandwidths are compatible and convenient for electronic sources in the terahertz region. This study also provides applications in THz sensing and imaging, communication and detection systems.

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