Conference Papers

Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/123456789/28506

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Author: search.filters.author.Krishnan, K.Has files: No

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    Comparison of OMP and SOMP in the reconstruction of compressively sensed hyperspectral images
    (2011) Aravind, N.V.; Krishnan, K.; Acharya, V.V.; Sumam David, S.
    In this paper, we present a novel method for the acquisition and compression of hyperspectral images based on two concepts - distributed source coding and compressive sensing. Compressive sensing (CS) is a signal acquisition method that samples at sub Nyquist rates which is possible for signals that are sparse in some transform domain. Distributed source coding (DSC) is a method to encode correlated sources separately and decode them together in an attempt to shift complexity from the encoder to the decoder. Distributed compressive sensing (DCS) is a new framework suggested for jointly sparse signals which we apply to the correlated bands of hyperspectral images. We compressively sense each band of the hyperspectral image individually and can then recover the bands separately or using a joint recovery method. We use the Orthogonal Matching Pursuit (OMP) for individual recovery and Simultaneous Orthogonal Matching Pursuit (SOMP) for joint decoding and compare the two methods. The latter is shown to perform consistently better showing that the Distributed Compressive Sensing method that exploits the joint sparsity of the hyperspectral image is much better than individual recovery. © 2011 IEEE.
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    Remote Triggered Laboratory for Boost Converter Using LabVIEW
    (Springer Science and Business Media Deutschland GmbH, 2021) Ansal, V.; Remya, V.K.; Jagadeesh, V.K.; Krishnan, K.
    This paper aims to provide remote access to laboratories in power electronics to all levels from under graduate to research. The platform is focused on learning aspect as much as performing the experiments. Remote triggered power electronics laboratory for boost converter experiments has been developed using National Instruments(NI) data acquisition device myRIO and LabVIEW software package which has an extensive support for interfacing devices and instruments. LabVIEW software is used to access the data using myRIO which has both the processor and Field Programmable Gate Array (FPGA). Through Graphical User Interface (GUI), a user in remote location is able to vary parameter pertaining to boost converter circuit which is transmitted to laboratory PC that has NI LabVIEW installed in it. The input is further fed to circuit, and then, output is fed back to LabVIEW through NI myRIO which ultimately is returned to user’s PC using web-publishing tool and can be viewed through GUI. Remote Triggered (RT) power electronics laboratories can be effectively used to give laboratory demonstrations to large number of learners. © 2021, Springer Nature Singapore Pte Ltd.
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    BER Performance Analysis of Optical Wireless Communication System over Weak and Strong Underwater Turbulence Channels
    (Springer Science and Business Media Deutschland GmbH, 2023) Naik, R.P.; Shripathi Acharya, U.S.; Bhargava Kumar, L.B.; Krishnan, K.; Chung, W.-Y.
    In this paper, we have investigated the performance of an underwater wireless optical communication (UWOC) link employing single-input and single-output (SISO) and selection combining (SC) as receiver diversity for varying link-ranges. As the the link-range increases, then strength of turbulence between the underwater optical entities also increases. It is assumed that the distribution of light propagation in weak and strong turbulence UWOC channel as log-normal (LN) and gamma-gamma (GG) density functions, respectively. The analytical bit error rate (BER) equations of on–off keying modulated UWOC link have been derived for SISO and SC receiver diversity using hyperbolic tangent distribution for LN and power series for GG density functions. The analytical BER results are validated with the Monte Carlo simulations. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
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    Outage Probability Analysis of Variable and Fixed Gain Relay-Assisted Dual-Hop RF-FSO Links Using Space–time Block Code Users
    (Springer Science and Business Media Deutschland GmbH, 2023) Naik, R.P.; Bhargava Kumar, L.B.; Krishnan, K.; Chung, W.-Y.
    In this paper, we have implemented an analytical study on a relay-assisted dual-hop system using fixed and variable gains for the radio-frequency (RF) and free-space optical communication (FSO). RF and FSO links are realized using the Rayleigh and Malaga distribution functions. Simulation results shows that pointing errors become severe, system performance deteriorates, and conjointly that the RF users exploiting space–time block coding (STBC) will enhance the performance of the end-to-end system. Outage probability of the end-to-end communication link operated with the STBC using the variable and fixed gain system implemented and plotted with respect to average SNR. From the obtained results, fixed gain relay-based communication link performs better efficient than the variable gain relay system. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
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    Switchable Wideband phase Gradient Beam Steering Reflector/Absorber for Applications such as Intelligent Reflecting Surfaces
    (Institute of Electrical and Electronics Engineers Inc., 2023) Janawade, S.A.; Krishnan, K.; Kandasamy, K.
    A miniaturized dual functional phase gradient meta-structure for beam steering and simultaneous RCS reduction is proposed in this work. A unit cell is designed, which generates a complete phase profile from -90° to 90° to direct the incident beam in all directions. The novelty in the proposed work is that the realized unit cell can reflect incident EM waves with 99.9% efficiency over a wide range of frequencies from 1 Hz to 40 GHz. Also, when the unit cell is loaded with lumped elements like a resistor and capacitor, it acts as an absorber. The magnitude of absorption is controlled by resistor, which can be varied from 79.17% to 99.97%, whereas the frequency at which absorption occurs can be tuned by varying capacitance. This unit cell configuration could achieve beam steering at sub 6 GHz, K and Ka-band frequencies. The dimensions of the proposed meta-atom is 8.4x8.4x1.56 mm3 and formulated on Rogers RT duroid 5880. © 2023 IEEE.