S. Chakraborty

Georgia Institute of Technology, Atlanta, GA, United States

Are you S. Chakraborty?

Claim your profile

Publications (46)16.62 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: In this article, we describe a method used to prepare an in situ sodium-activated, organomodified bentonite clay/styrene–butadiene rubber nanocomposite master batch via a latex blending technique. The clay master batch was used for compound formulation. Octadecyl amine was used as an organic intercalate. The clay was purchased from local suppliers and was very cheap. Sodium chloride was used for in situ activation of the clay. The wide-angle X-ray diffraction data indicated that the in situ sodium activation helped to increase the intergallery distance from 1.28 to 1.88 nm. A transmission electron micrograph indicated intercalation and partial exfoliation. The thermal properties were relatively better in the case of the sodium-activated, organomodified bentonite-clay-containing compound. A substantial improvement in physical properties such as the modulus, tensile strength, tear strength, and elongation at break was observed in the case of the in situ sodium-activated compound. A cation-exchange capacity equivalent (of the clay) of 1.5 times the octadecyl amine was the optimum dose for the modification. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
    Journal of Applied Polymer Science 07/2009; 113(2):1316 - 1329. · 1.40 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: This paper reports a fully monolithic subthreshold CMOS receiver with integrated subthreshold quadrature LO chain for 2.4 GHz WPAN applications. Subthreshold operation, passive voltage boosting, and various low-power circuit techniques such as current reuse, stacking, and differential cross coupling have been combined to lower the total power consumption. The subthreshold receiver, consisting of the switched-gain low noise amplifier, the quadrature mixers, and the variable gain amplifiers, consumes only 1.4 mW of power and has a gain of 43 dB and a noise figure of 5 dB. The entire quadrature LO chain, including a stacked quadrature VCO and differential cross-coupled buffers, also operates in the subthreshold region and consumes a total power of 1.2 mW. The subthreshold receiver with integrated LO generation is implemented in a 0.18 mum CMOS process. The receiver has a 3-dB IF bandwidth of 95 MHz.
    IEEE Journal of Solid-State Circuits 11/2008; · 3.06 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: According to the KEMI report, products with polycyclic aromatic compounds, PCA, levels exceeding 3% by weight must be labelled. The report pointed out that worn tyre tread material was being spread on the roadsides, introducing high amounts of PCA into the environment. PCA is having toxic effects on aquatic organisms. Polyaromatic-hydrocarbon-rich extender oils are to be banned by December 2009, which gives rise to challenges for the oil and rubber industries. In the present work, 10 types of naturally occurring oils and six types of petroleum-based oils were characterised in natural-rubber-based truck tyre tread cap compound. Compounds made with some of the naturally occurring oils showed better mechanical and dynamic mechanical properties.
    Polymer Testing. 05/2008;
  • [Show abstract] [Hide abstract]
    ABSTRACT: A SiGe sub-harmonic down-conversion mixer using a novel active anti-parallel diode pair is presented for millimeter-wave applications. The proposed architecture can help reduce conversion loss and also lower the required local oscillator power. With an LO power of 0 dBm, the measured 2times conversion gain varies from -5 to -7.8 dB in the 50 to 65 GHz range. Compared to earlier reports of millimeter-wave SiGe and GaAs sub-harmonic mixers requiring 5 to 10 dBm of LO power, this circuit achieves similar conversion loss with an LO power as low as -7.5 dBm, while consuming only 0.5 mW of DC power.
    Microwave Integrated Circuit Conference, 2007. EuMIC 2007. European; 11/2007
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The invention of Nylon-6/clay nanocomposites by the Toyota Research Group of Japan heralded a new chapter in the field of polymer composites. This article highlights the work done in the field of rubber/clay nanocomposites. The preparations of rubber/clay nanocomposites by solution blending, latex compounding, and melt intercalation are covered and a thorough discussion of the mechanical properties of the various rubber/clay nanocomposite systems is presented. Other properties such as barrier, dynamic mechanical behavior, and thermal properties are also discussed. Finally, the future trends in the rubber/clay nanocomposites are mentioned. POLYM. ENG. SCI., 47:1956–1974, 2007. © 2007 Society of Plastics Engineers
    Polymer Engineering and Science 10/2007; 47(11):1956 - 1974. · 1.24 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Infrared spectroscopy can be used efficiently by polymer and rubber technologists for identification of polymer, polymer–blend ratio calculation, raw material evaluation, study of reaction mechanism, microstructure determination, etc. The present article represents a method to characterize nitrile rubber by Fourier-transformed infrared spectrophotometry (FTIR). The absorbance ratio of specific peaks of different grades of nitrile rubber was correlated with the acrylonitrile content measured by the Kjeldhal method. The acrylonitrile content of unknown acrylonitrile butadiene rubber (nitrile rubber, NBR) was calculated from a calibration graph.
    Polymer Testing. 02/2007;
  • [Show abstract] [Hide abstract]
    ABSTRACT: Polyaromatic hydrocarbon-rich extender oils are to be banned by December 2009 which gives rise to challenges for the oil and rubber industries. In the present work, 10 types of naturally occurring oils and six types of petroleum-based oils were characterized for chemical and physical properties. The effect of these process oils in natural rubber-based truck-tyre tread cap compound was also studied. Some of the naturally occurring oils showed better processing properties, polymer–filler interaction and dispersion properties.
    Polymer Testing 01/2007; 26(4):489-500. · 1.65 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In this study, an attempt has been made to correlate the polydispersity value measured through gel permeation chromatography (GPC) and that obtained through rubber process analyzer (RPA 2000). The tan&dgr; at higher and lower frequencies is measured using RPA 2000. The inverse of tan&dgr; difference at higher and lower frequencies obtained through RPA 2000 is correlated with the polydispersity data measured from GPC for different grades of raw rubbers like ethylene propylene diene rubber (EPDM) and butyl rubber (IIR). Polydispersity as predicted by RPA 2000 shows excellent correlation with that measured through GPC. The coefficient of correlation is found to be 0.98 for EPDM and 0.99 for IIR. The predicted polydispersity value obtained through RPA 2000 is within ±8% from that measured through GPC.
    Journal of Elastomers and Plastics 01/2006; 38(1):31-41. · 0.62 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In the present study, the molecular weight of 4-alkyl phenol formaldehyde resin (MP resin) was determined by gel permeation chromatography (GPC). The weight average molecular weight of MP resin obtained was correlated with the ball & ring softening point and methylol content. The correlation coefficients found were 0.989 and 0.997, respectively. The maximum variation in predicted value of ball & ring softening point was ±3.35%-and that of methylol content was ±7.00%.
    Polymer Testing - POLYM TEST. 01/2006; 25(1):12-15.
  • [Show abstract] [Hide abstract]
    ABSTRACT: In the present study, coagulated styrene-vinylpyridine-butadiene ter-polymer latex (VP latex) is used as a secondary accelerator to increase the cure rate in the sulfonamide—sulfur curing system in natural as well as synthetic rubber-based compounds. The activation energy is observed to be lower when coagulated VP latex is used as a secondary accelerator. All other physical properties are observed to be comparable. It is found that a small amount of coagulated VP ter-polymer is sufficient to increase the reaction rate. However, it is also found that coagulated VP latex alone is not a satisfactory accelerator.
    Journal of Elastomers and Plastics 01/2006; 38(3):249-260. · 0.62 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In the present study the effect of metal poisoning was studied in a natural rubber (NR)–based tire-tread compound. The experimental compound contained 1000 ppm copper metal as an additional ingredient. A detailed study was carried out and the results of the experimental compound were compared against a control compound having no metal ion. The effect of metal poisoning was not significant in the case of the green experimental compound, even after prolonged storage of 150 days. However, the cured experimental compound deteriorated substantially after ageing in aerobic-, anaerobic-, oil-, and outdoor-ageing conditions. The ozone resistance property of the experimental compound also proved to be inferior. The degradation kinetic of metal poisoning was found to be a first-order reaction and the service life (as expressed by the half-life period) was drastically reduced for the poisoned compound. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1492–1499, 2005
    Journal of Applied Polymer Science 08/2005; 98(4):1492 - 1499. · 1.40 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A CMOS subharmonic mixing technique based on threshold voltage modulation with higher LO-to-RF isolation is presented in this paper. A 2.1GHz subharmonic mixer is designed using this technique in a 0.18μm standard digital CMOS process by applying the LO signals at the bulk terminal of PMOS transistors. The mixer has a measured conversion gain of 10.5dB, an IIP3 of -3.5dBm, and a noise figure of 17.7dB while consuming 2.5mW in each mixer core. This circuit architecture increases the second harmonic LO-to-RF isolation to above 67dB and hence can mitigate LO leakage issues in wireless receivers.
    Microwave Symposium Digest, 2005 IEEE MTT-S International; 07/2005
  • [Show abstract] [Hide abstract]
    ABSTRACT: Amplifier design techniques are presented for reducing dc power consumption in wireless PAN transceivers. A CMOS VGA cell is implemented by combining two independent gain control circuits to obtain 40dB and 50dB (dB-linear) gain ranges at 250μW and 1.75mW, respectively. A 260μW, 1GHz CMOS LNA is designed by using an unrestrained subthreshold bias technique to improve linearity. It has a measured gain of 13.6dB, a noise figure of 4.6dB and an IIP3 of 7.2dBm. An inductor-less RF VGA cell, based on a TA-TI pair, with 20dB gain range is also presented as an example of system level power optimization.
    Microwave Symposium Digest, 2005 IEEE MTT-S International; 07/2005
  • [Show abstract] [Hide abstract]
    ABSTRACT: A micro-power complementary metal oxide semiconductor (CMOS) low-noise amplifier (LNA) is presented based on subthreshold MOS operation in the GHz range. The LNA is fabricated in an 0.18-μm CMOS process and has a gain of 13.6 dB at 1 GHz while drawing 260 μA from a 1-V supply. An unrestrained bias technique, that automatically increases bias currents at high input power levels, is used to raise the input P1dB to -0.2 dBm. The LNA has a measured noise figure of 4.6 dB and an IIP3 of 7.2 dBm.
    IEEE Microwave and Wireless Components Letters 07/2005; · 1.78 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Not Available
    Microwave Conference, 2004. 34th European; 11/2004
  • [Show abstract] [Hide abstract]
    ABSTRACT: Not Available
    Radio and Wireless Conference, 2004 IEEE; 10/2004
  • Y. Park, S. Chakraborty, C.-H. Lee, S. Nuttinck, J. Laskar
    [Show abstract] [Hide abstract]
    ABSTRACT: We present the design, implementation, and measurement of a fully integrated wide-band (3.3GHz-4GHz) CMOS VCOs and frequency divider, as well as the analysis and comparison of VCO topologies for their uniform phase noise performance in the wide tuning range. In addition, the dynamic range of the frequency divider is analyzed based on experimental results for the first time. The different VCO topologies have been investigated by using the measured results. It is demonstrated that the NMOS-PMOS VCO (NP-core VCO) without a current source has as low as 2dB of phase noise variation in the entire tuning range of 650MHz as well as achieving superior phase noise performance of -118.5 dBc/Hz at 1MHz offset compared to the NMOS VCO (N-core VCO) which shows severe phase noise degradation of 17dB due to AM-FM conversion in the high varactor gain region. A frequency divider is designed to generate the quadrature signal for direct conversion. The measured results exhibit the dynamic range limit of the frequency divider along with sensitivity curve of the divider. To the best of our knowledge, this is the first report analyzing the dynamic range of the frequency divider based on the experimental results.
    Microwave Symposium Digest, 2004 IEEE MTT-S International; 07/2004
  • Joy Laskar, Babak Matinpour, Sudipto Chakraborty
    [Show abstract] [Hide abstract]
    ABSTRACT: This chapter describes the theory, design, fabrication and measurements on subharmonic receivers. This type of receivers are becoming increasingly attractive for next generation wireless receivers in multigigahertz regime. First, theoretical principles of subharmonic receiver and frequency planning is presented, followed by the specific circuit demonstrations, along with system considerations. Implementation in silicon based technologies is addressed as well. Finally, a demonstration of C-band direct conversion receiver implemented in GaAs MESFET technology is provided for better understanding and appreciation of the techniques discussed.
    03/2004: pages 83 - 126; , ISBN: 9780471474852
  • Joy Laskar, Babak Matinpour, Sudipto Chakraborty
    [Show abstract] [Hide abstract]
    ABSTRACT: This chapter provides a step by step example of a direct conversion receiver front-end in SiGe BiCMOS process. At first, the system calculations are described, followed by the circuit design approaches. Afterwards, the design and simulation steps relevant to the design of such receiver is addressed in details. Necessary characterization steps are demonstrated afterwards, with specific discussions on the measurement results for two different types of direct conversion receivers operating at 5–6 GHz frequency range. This chapter could be used to mimic a class project for integrated receiver subsystems design from scratch.
    03/2004: pages 47 - 81; , ISBN: 9780471474852
  • Chapter: Frontmatter
    Joy Laskar, Babak Matinpour, Sudipto Chakraborty
    03/2004: pages i - xiii; , ISBN: 9780471474852