http://starc.stthomas.ac.in:8080/xmlui/xmlui/handle/123456789/134 2026-04-16T23:13:28Z 2026-04-16T23:13:28Z Bindu, C. Chakyar, Sreedevi P. Sebastian, Anju Simon, Sikha K. Jose, Jovia Paul, Nees Umadevi, K. S. Kizhakooden, Joe Andrews, Jolly Joseph, V. P. http://starc.stthomas.ac.in:8080/xmlui/xmlui/handle/123456789/379 2025-01-16T08:00:29Z 2019-10-19T00:00:00Z

Enhancing the resolution in imaging using folded metamaterial split ring resonator structure at microwave frequencies Bindu, C.; Chakyar, Sreedevi P.; Sebastian, Anju; Simon, Sikha K.; Jose, Jovia; Paul, Nees; Umadevi, K. S.; Kizhakooden, Joe; Andrews, Jolly; Joseph, V. P. A novel and better resolution topology for reducing the sensing area of conventional Split Ring Resonator (SRR) metamaterial structure is proposed. The conventional planar SRR structure is fabricated on a thin flexible film and is folded to raise its split region slightly up with respect to the plane of the SRR (Folded Split Ring Resonator-FSRR).The structure exhibits strong localization of electric field in the projected region of the sensor, by confining the evanescent waves in that region having dimension much smaller than the operating wavelength. The proposed sensor is placed between transmitting and receiving probes of a Vector Network Analyzer (VNA) to form the sensing probe. Two dielectric samples arranged at different distances of separation are scanned and the corresponding transmission characteristics S21 are drawn for analysing the image resolution. The resolution and sensitivity of the above proposed sensor is compared with conventional SRR and is found to be superior in performance. This novel FSRR provides a better resolution and thereby overcomes the diffraction limit in imaging up to λ/30, whereas for the conventional planar SRR it will be around λ /15. The design is simple, compact and inexpensive. The potential of proposed sensor can be extended to sub-wavelength imaging of dielectric materials, biological samples and can be used for non-destructive testing.

2019-10-19T00:00:00Z Paul, Nees Jimmy, Janet Chakyar, Sreedevi P Simon, Sikha K Kizhakooden, Joe Bindu, C Sebastian, Anju Umadevi, KS Jose, Jovia Andrews, Jolly Joseph, VP http://starc.stthomas.ac.in:8080/xmlui/xmlui/handle/123456789/206 2022-03-04T09:42:43Z 2019-10-29T00:00:00Z

Microwave absorption properties of flexible zinc oxide sheet Paul, Nees; Jimmy, Janet; Chakyar, Sreedevi P; Simon, Sikha K; Kizhakooden, Joe; Bindu, C; Sebastian, Anju; Umadevi, KS; Jose, Jovia; Andrews, Jolly; Joseph, VP This paper presents the fabrication and microwave absorption properties of low-cost flexible light-weight zinc oxide (ZnO) sheet. The elastomers, films and foams used as microwave absorbers are made of lossy materials impregnated on low density matrixes which are thicker, heavier and expensive in wide frequency ranges. The prepared ZnO sheet in polytetrafluoroethylene (PTFE) matrix and isopropyl alcohol (IPA) as binder is characterized using XRD which showed the crystalline structure of ZnO in the sample. The microwave characterization is done using waveguide method by placing the sheet samples of different thickness (1 mm and 2 mm) perpendicular to the direction of propagation of power inside the rectangular wave-guides with operating frequency ranges of 5 - 7 GHz and 7 - 9 GHz connected to a Vector Network Analyzer (VNA). Transmission (S21) and reflection (S11) coefficients are analyzed in the above frequency ranges. The reflection coefficients show no remarkable variation throughout the measured frequency range whereas the transmission coefficients exhibit noticeable drop in the transmitted power around 5 - 15 dB at certain frequencies. As the thickness of the sample increases, the absorption level also increases. The absorption of microwave power is observed to be maximum at 8 - 9 GHz frequency range. Absorption properties of conducting ZnO sheet may find applications in the design of novel type of microwave absorbers

2019-10-29T00:00:00Z Jose, Jovia Simo, Sikha K Sebastian, Anju Chakyar, Sreedevi P Kizhakooden, Joe Paul, Nees Bindu, C Umadevi, KS Andrews, Jolly Joseph, VP http://starc.stthomas.ac.in:8080/xmlui/xmlui/handle/123456789/203 2022-03-04T09:03:25Z 2019-10-29T00:00:00Z

Scattering from artificial plasma cylinder using nonstandard FDTD Jose, Jovia; Simo, Sikha K; Sebastian, Anju; Chakyar, Sreedevi P; Kizhakooden, Joe; Paul, Nees; Bindu, C; Umadevi, KS; Andrews, Jolly; Joseph, VP This paper implements Nonstandard Finite Difference Time Domain (NS-FDTD) method to analyses the scattering effect of electromagnetic wave by an artificial plasma cylinder. This NS-FDTD which requires less iteration time for convergence has proved to be around 10,000 times more accurate than the standard FDTD. For a chosen problem, the ratio between wave length and grid space in NS-FDTD need to be only 8 whereas for the standard algorithm it has to be 1140 for the same qualitative result. In this paper, NS-FDTD algorithm which is already successfully implemented for lossless and low loss medium is extended to high loss medium. An artificial negative permittivity metamaterial medium of cylindrical profile is designed using periodic arrangement of thin conducting wires and NS-FDTD is used to study the scattering properties of the plasma structure. For simplicity, interacting field quantities are realized in terms of propagation equation. Converging points of stability function are carefully selected by choosing appropriate value of conductivity. Plane wave of frequency less than the plasma frequency of the artificial plasma cylinder is used for the study. The result obtained is compared with standard FDTD which proves the obvious advantage of using this novel algorithm.

2019-10-29T00:00:00Z Kizhakooden, Joe Jose, Jovia Paul, Nees Chakyar, Sreedevi P Sebastian, Anju Simon, Sikha K Umadevi, KS Bindu, C Andrews, Jolly Joseph, VP http://starc.stthomas.ac.in:8080/xmlui/xmlui/handle/123456789/199 2022-03-04T07:07:03Z 2019-10-29T00:00:00Z

Broadside coupled split ring resonator based multiband monopole patch antenna for wireless communication applications Kizhakooden, Joe; Jose, Jovia; Paul, Nees; Chakyar, Sreedevi P; Sebastian, Anju; Simon, Sikha K; Umadevi, KS; Bindu, C; Andrews, Jolly; Joseph, VP The present work reports the development of a multiband monopole patch antenna by utilizing Broadside Coupled Split Ring Resonator (BCSRR) units. This antenna makes use of the resonant property of metamaterial BCSRR units for multiband frequency designing. Since the magnetic resonant frequency of the BCSRR depends on the effective capacitance and inductance of its rings, the geometrical parameters of the rings like inter planar distance between them, inner and outer radii, split widths and the dielectric material between the rings play important role in designing the radiating frequency bands of the proposed antenna. The desired frequencies for potential applications like Bluetooth, Wi-Fi and Wi-Max are thus achieved by proper designing of the BCSRR units. In this work, it is demonstrated that two additional frequencies can be radiated along with the monopole radiation by coupling two BCSRR units to the monopole. The fabricated antenna exhibits high return loss at 2.45 GHz and 2.75 GHz along with the monopole radiation around 5 GHz. The number of operating frequencies can be increased by adding more BCSRR units at various positions near to the monopole patch. The proposed antenna is compact, light weight and easy to design and fabricate when compared with the recently reported multiband monopole antennas. The good agreement between the experimental and simulated results shows that the proposed antenna is a suitable candidate for potential wireless applications. The different antennas for different applications in a single device can be replaced with the single proposed antenna.

2019-10-29T00:00:00Z