http://starc.stthomas.ac.in:8080/xmlui/xmlui/handle/123456789/371 Thu, 16 Apr 2026 23:12:20 GMT 2026-04-16T23:12:20Z http://http://starc.stthomas.ac.in:8080/xmlui:8080/xmlui/bitstream/id/168fff29-d802-4617-bc09-99bb4a7b229e/ http://starc.stthomas.ac.in:8080/xmlui/xmlui/handle/123456789/371 http://starc.stthomas.ac.in:8080/xmlui/xmlui/handle/123456789/388 Breaking the Diffraction Limit Manifold Using Specially Designed Metamaterial Split Ring Resonator Bindu, Cherala; Simon, Sikha K.; Sebastian, Anju; Aswathi, Panattil V.; Joseph, Dona; Andrews, Jolly; Joseph, Vallikkavumkal P. A novel and efficient method to overcome the barriers of conventional diffraction limit using a specially designed metamaterial Split Ring Resonator (SRR) structure as an imaging sensor at microwave frequency is proposed. The topology of the proposed sensor is ingeniously designed to identify imaging objects having dimensions much less than the interacting wavelength λ. The split gap field region of the conventional SRR, used as the sensing region of the imaging sensor, is modified for enhancing the resolution capacity, by slightly raising the split region of the outer ring structure perpendicular to the plane of the resonator (Projected Split Ring Resonator — PSRR) which will reduce the area of the sensing region of the SRR probe considerably. The isolation of the structural parts of the SRR other than projected split region helps in using the localized evanescent field at the split region of the PSRR for imaging of minute objects having dimension ranges up to 0.0001λ by precisely choosing the split gap. The required projection height of the split region and the possible resolution limits of the PSRR sensor probe are evaluated by simulation. Experimental 2-dimensional sub-wavelength images obtained for various dielectric objects using a typical PSRR test probe having resolution capability up to 0.01λ are also presented. Fri, 01 Jan 2021 00:00:00 GMT http://starc.stthomas.ac.in:8080/xmlui/xmlui/handle/123456789/388 2021-01-01T00:00:00Z http://starc.stthomas.ac.in:8080/xmlui/xmlui/handle/123456789/380 Wide Band Microwave Absorber using Flexible Broadside Coupled Split Ring Resonator Metamaterial Structure Umadevi, K. S; Simon, Sikha K.; Chakyar, Sreedevi P.; Andrews, Jolly; Joseph, V. P. This paper proposes a wide band microwave absorber in a bulk form realized using a Broad Side Coupled Split Ring Resonator (BCSRR) metamaterial structural units fabricated in a novel way which possesses structural flexibility and wide band frequency tunability. Instead of using a conventional structure, the two conducting rings of the structure are prepared separately by photochemical etching using thin copper sheets glued on polypropylene film. The resonant property studies of the BCSRR show a noticeable tunability in resonant frequency with spacing variation, a result not observed using other conventional SRR structures. A spacing variation of 1 mm of a typical BCSRR unit shows around 3 GHz resonant tunability which makes it suitable for materializing various sensor applications. The resonant properties of BCSRR in a bulk form made with specific structural dimensions arranged in periodic manner with progressively varying spacing using layers of cotton fabric, show wide band resonant absorption. By suitably modifying the structural parameters of BCSRR rings, the range of the frequency absorption band can be specifically designed. The result of the study predicts a possibility of using this proposed BCSRR designs in various types of wide band absorbers. Thu, 14 Nov 2019 00:00:00 GMT http://starc.stthomas.ac.in:8080/xmlui/xmlui/handle/123456789/380 2019-11-14T00:00:00Z http://starc.stthomas.ac.in:8080/xmlui/xmlui/handle/123456789/379 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. Sat, 19 Oct 2019 00:00:00 GMT http://starc.stthomas.ac.in:8080/xmlui/xmlui/handle/123456789/379 2019-10-19T00:00:00Z http://starc.stthomas.ac.in:8080/xmlui/xmlui/handle/123456789/206 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 Tue, 29 Oct 2019 00:00:00 GMT http://starc.stthomas.ac.in:8080/xmlui/xmlui/handle/123456789/206 2019-10-29T00:00:00Z