Faculty Publications
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Item Fabrication and characterisation of RF MEMS capacitive switches tuned for X and Ku bands(Inderscience Publishers, 2018) Shajahan, E.S.; Bhat, M.S.Microelectromechanical systems (MEMS) capacitive switches discussed in this paper employ electrostatic actuation to perform switching. Capacitive switches employ inductive tuning for excellent switching characteristics in X and Ku bands. Employing inductive tuning is found to increase the switch beam inductance by a few tens of pico-henry. This enhances the Q factor and enables tuning of isolation over a narrow band of frequencies. Beam inductance can be extracted from the simulated isolation characteristics of the switch by curve fitting. This paper presents design, fabrication and characterisation of inductive tuned MEMS capacitive switches tuned for X and Ku bands. The devices are fabricated on high resistive (10 KΩ) silicon substrate by a five mask process. The characterisation of the fabricated devices are conducted using Cascade probe station and high frequency Power network analyser. Characterisation results show an actuation voltage of 18.5 volts. The insertion - loss and isolation are better than 0.5 dB and -40 dB respectively in the 8-18 GHz band. © © 2018 Inderscience Enterprises Ltd.Item Experimental investigation of torsional vibration isolation using Magneto Rheological Elastomer(EDP Sciences edps@edpsciences.com, 2018) Shenoy, K.; Singh, A.K.; Sai Aditya Raman, K.; Gangadharan, K.V.Rotating systems suffer from lateral and torsional vibrations which have detrimental effect on the roto-dynamic performance. Many available technologies such as vibration isolators and vibration absorbers deal with the torsional vibrations to a certain extent, however passive isolators and absorbers find less application when the input conditions are dynamic. The present work discusses use of a smart material called as Magneto Rheological Elastomer (MRE), whose properties can be changed based on magnetic field input, as a potential isolator for torsional vibrations under dynamic loading conditions. Carbonyl Iron Particles (CIP) of average size 5 μm were mixed with RTV Silicone rubber to form the MRE. The effect of magnetic field on the system parameters was comprehended under impulse loading conditions using a custom built in-house system. Series arrangement of accelerometers were used to differentiate between the torsional and the bending modes of vibration of the system. Impact hammer tests were carried out on the torsional system to study its response, in the presence and absence of magnetic field. The tests revealed a shift in torsional frequency in the presence of magnetic field which elucidates the ability of MRE to work as a potential vibration isolator for torsional systems. © The Authors, published by EDP Sciences, 2018.Item High Isolation Single Pole Four Throw RF MEMS Switches for X band(Institute of Electrical and Electronics Engineers Inc., 2018) Shajahan, E.S.; Bhat, M.S.This work presents low loss RF-MEMS Single Pole Four Throw (SP4T) switch for X band. The present work is inspired from the fact that electrostatically actuated RF MEMS switches have superior RF performance over the state-of-the-art solid-state switches. Since an optimized design for Single Pole Multi Throw (SPMT) switch is difficult to realize, this work proposes a new design to achieve low loss and high isolation. The idea is to realize a combination of SPST (Single-Pole-Single-Throw) series and shunt switching in each arm of the SP4T model. The actuation voltage, isolation and insertion losses are optimized. The electro-mechanical modeling of the proposed device is done in CoventorWare and electro-magnetic modeling in HFSS. The simulation of the proposed design shows an actuation voltage of 12 V for capacitive shunt configuration and 13.75 V for the lateral series switch. The insertion loss and isolation are better than 1 dB and -50 dB respectively in the X band. The excellent RF characteristics make the switches suitable as MEMS varactors for high frequency applications and in tunable MEMS filters and phaseshifters. © 2018 IEEE.Item Multiport Converters to Integrate Multiple Sources and Loads - A Review of Topologies(Institute of Electrical and Electronics Engineers Inc., 2018) Adarsh, S.; Nagendrappa, N.With the increase in penetration of variety of renewable energy resources in the grid, energy storage systems are needed to balance power flow and improve the reliability of the system. A compact multiport converter supporting bidirectional power flow is a suitable candidate to interface multiple sources and loads. This paper reviews various multiport converter topologies in the literature. The multiport converters can be classified as isolated, partially isolated and non isolated converters. The converter topologies in each category are identified and reviewed. Their benefits and drawbacks are highlighted. © 2018 IEEE.Item A Study on Trenching Techniques for Vibration Isolation: An Overview(Springer Science and Business Media Deutschland GmbH, 2021) Bariker, P.; Kolathayar, S.This paper presents a detailed review of past research studies on trenching techniques for vibration isolation. With rapid urbanization and fast-growing infrastructures in developing countries like India, it is very likely for many structures subject to vibrations from earthquakes, traffic movements, or machine vibrations. Though the trench technique for vibration screening is an established technique, there has been a lot of advancements in vibration screening in recent years. This paper presents an overview of the developments in trenching techniques for vibration screening from its inception to the latest advancements. The studies have been categorized into laboratory element/model tests, field tests, and numerical analyses. The review of studies highlights that the open trenches perform better isolation for shallow depths whereas the infilled trenches perform better than open trenches when the normalized depth of trench is deeper. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item A Wideband Microstrip Line-Based Balun Structure for High Power Amplifier Applications(Springer Science and Business Media Deutschland GmbH, 2023) Gupta, M.P.; Gorre, P.; Kumar, S.; Song, H.This paper proposes a balun matching technique to achieving a high output power and wide bandwidth. The proposed structure includes microstrip transmission line-based even and odd mode-matching circuits. A three-port unipolar microstrip line is designed to transform the balanced load termination to 50 Ω unbalanced port impedance. The proposed network design is based on real symmetrical four port network with open ended transmission line is inserted between the middle of the structure. To improve the isolation, transmission coefficient parameter and match the 50 Ω termination, a resistive network is inserted between the two balanced ports. The proposed structure is simulated in Keysight Technologies Advanced Design System (ADS), fabrication is done by using 0.51 mm RT Duriod substrate alignments. To verify the design concept, first of all, a wideband microstrip matching technique is designed and characterized at the frequency of L5 band (1.17 GHz). Then a prototype of microstrip transmission line-based wideband balun matching circuit is designed and fabricated. Analytical design equations have been derived for the even mode as well as odd mode techniques which satisfied the results. The proposed balun could overcome power loss mechanism over traditional transmission line structures and can utilize for high power application. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item Design and Analysis of Wide-Band Circularly Polarized 2×2 Mimo Antenna for Sub-6 Ghz 5G Communication(Institute of Electrical and Electronics Engineers Inc., 2025) Soniya, S.S.; Yashaswini, H.M.; Bhavyashree, K.V.; Deepika, P.N.; Tharehalli Rajanna, P.K.T.; Kandasamy, K.This work presents a 2×2 circularly polarized (CP) MIMO microstrip antenna. The square slot antenna's corner is perturbed, resulting in two degenerative modes necessary for CP achievement. To achieve MIMO features, the corner perturbed slot antenna is placed in a 2×2 consecutive configuration. The slot antenna is fed by the microstrip line. The two degenerated modes of single slot antenna will provide wide axial ratio bandwidth of 29.3%. The suggested MIMO antenna provides improved impedance bandwidth (48.21%), axial ratio bandwidth, gain, and port isolation. The antenna radiates in the broadside direction and has higher cross polarization levels than copolarization values. Total active reflection coefficient (TARC), Envelop correlation coefficient (ECC) and diversity gain (DG) of the proposed design are evaluated. The proposed design is well suitable in sub-6 GHz 5G application. © 2025 IEEE.Item Calcium oxalate degrading thermophilic oxalate oxidase from newly isolated Fusarium oxysporum RBP3(Elsevier Ltd, 2020) Kizhakedathil, M.P.; Bose, R.; Belur, P.D.Four oxalate oxidase (OxO) positive fungal strains were isolated from rotting taro corms. One isolate showing highest extra cellular OxO titre was selected and was identified based on partial sequencing of 18S rRNA. The selected strain was found to be Fusarium oxysporum f. sp. cumini. Oxalate oxidase (EC 1.2.3.4) titre was increased by one factor at a time approach in shake flasks. The enzyme was then purified by isopropanol precipitation followed by chromatography using ENrich SEC650 FPLC column. OxO was found to be a heterodimer having two subunits of mass 116 and 105 kDa. Optimum pH and temperature were found to be 3.8 and 80 °C respectively. OxO exhibited stability for 4 h at temperature range of 4–95 °C and pH between 2.2 and 10.0. OxO was inactive until 30 °C and more than 90% of its peak activity was observed at temperature above 80 °C, suggesting that the enzyme is thermophilic. OxO appears to be a metalloprotein inhibited by Cu2+, Fe2+ and EDTA and enhanced in the presence of Mn2+ and biotin. OxO also exhibited broad substrate specificity. This enzyme was found to decompose insoluble calcium oxalate crystals. This is the first report of OxO decomposing calcium oxalate crystals. © 2020Item A low loss hexagonal six-port optical circulator using silicon photonic crystal(Springer, 2023) Sangeetha, S.; Vani, D.; Gupta, P.; Krishnan, P.A 6-port optical circulator using silicon photonic crystals has been designed and proposed in this paper as an essential component of an optical communication system. The proposed 6-port circulator has greater isolation values between the input and isolated ports and lower insertion loss values between the input and output ports. The proposed circulator achieves maximum isolation of 38.7 dB and minimum insertion loss of 0.0029 dB. The proposed designs are extremely useful in the telecommunications industry, wavelength division multiplexing and photonic integrated circuits applications due to their low insertion and high isolations. © 2023, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.Item Bioprospecting indigenous bacteria from landfill leachate for enhanced polypropylene microplastics degradation(Elsevier B.V., 2025) Dubey, A.P.; Thalla, A.K.Plastic pollution, especially microplastics (MPs), is a severe environmental threat. Due to the significant environmental issues posed by plastics, it is critical to use an effective and sustainable degradation technique. The study aimed to isolate and identify Indigenous bacterial strains from landfill leachate (LL) to evaluate its potential for degrading Polypropylene microplastics (PPMPs). The investigation identified two bacterial strains, Pseudomonas aeruginosa, and novel Staphylococcus haemolyticus, through 16S rRNA analysis, capable of decomposing PPMPs. Following a 30-day treatment period, it was noted that Staphylococcus haemolyticus reduced the dry weight of PPMPs by 25.46 % ± 1.35 %, whereas Pseudomonas aeruginosa strain reduced it by 7.01 % ± 0.85 %. Multiple tests, including weight loss, pH, optical density, total biomass yield, and BATH test of the medium, validated the growth of bacterial strains. The biochemical characteristics of the isolated strains were assessed through Biochemical tests. The study also investigated the surface, chemical, and structural changes in treated PPMPs using Scanning electron microscopy (SEM), Energy-Dispersive X-ray spectroscopy (EDS), X-ray diffractometer (XRD), and Ion Chromatography (IC) tests. The Fourier Transform Infrared Spectroscopy (FTIR) study also showed the creation of alcohol, methyl, as well as carbonyl groups due to hydrolysis and oxidation by both bacterial strains. This study implies that the Staphylococcus haemolyticus and Pseudomonas aeruginosa bacterial strains are secure and efficient for PPMP bioremediation. © 2025 Elsevier B.V.