Faculty Publications
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Item A new approach for channel blind identification based on second order cyclostationary statistics and the group delay has been proposed. In this, two methods are proposed. In both the methods, the correction is applied to the basic phase estimate for both the poles and zeros, in the group delay domain. The basic phase estimate is derived from the spectral correlation density (SCD) of the system output. In the first method, the phase correction is based on magnitude group delay. In the second method, not only the phase correction but also an improved system magnitude estimate of better variance and frequency resolution is derived based on modified magnitude group delay. The results indicate a significant improvement in performance for both the methods. For the first method in the absence of noise, the percentage normalized mean square error is reduced by about 85% over that of the existing non-parametric method. The second method in the presence of noise (SNR=5 dB), provides a reduction of 74% over the existing non-parametric method and 57% over the existing combined parametric and non-parametric methods. © 2005 Elsevier B.V. All rights reserved.(Channel blind identification based on cyclostationarity and group delay) Narasimhan, S.V.; Hazarathaiah, M.; Giridhar, P.V.S.2005Item The third-order nonlinear optical properties of novel styryl dyes(2009) Shettigar, S.; Umesh, G.; Poornesh, P.; Manjunatha, K.B.; Asiri, A.M.The third-order nonlinear optical properties of two novel styryl dyes, namely, 1,3-diethyl-5-(4-methoxybenzylidene)-2-thioxodihydropyrimidine-4,6(1H,5H)-dione and 5-(3,4-dimethoxybenzylidene)-1,3-diethyl-2-thioxodihydropyrimidine-4,6(1H,5H)-dione were studied using the Z-scan technique employing 7 ns laser pulses at 532 nm. The nonlinear refractive index, nonlinear absorption coefficient, magnitude of effective third-order susceptibility and coupling factor were determined. The optical power limiting behavior of the colorants was ascribed to two-photon absorption phenomenon. Nonlinear absorption cross-section increased with increase in ? electron density and the effective two-photon absorption cross-section was two orders of magnitude larger than those of commercially available azo compounds. The results suggest that these colorants offer promise as nonlinear optical materials for device applications. © 2009 Elsevier Ltd. All rights reserved.Item Enhancing the error-correcting capability of imai-kamiyanagi codes for data storage systems by adopting iterative decoding using a parity check tree(2012) Kumar, H.; Sripati, U.; Rajesh Shetty, K.; Shankarananda, B.A novel low-complexity, soft decision technique which allows the decoding of distance-5 double error-correcting Imai-Kamiyanagi codes by using a parity check tree associated with the Tanner graph is proposed. These codes have been applied to memory subsystems and digital storage devices in order to achieve efficient and reliable data processing and storage. For the AWGN channel, gains in excess of 1.5 dB at reasonable bit error rates with respect to conventional hard decision decoding are demonstrated for the (46, 32), (81, 64), and (148, 128) shortened Imai-Kamiyanagi codes. Copyright © 2012 by the IETE.