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Chayratsami P.,King Mongkut Institute of Technology Ladkrabang | Thuaykaew S.,Celestica Inc.
International Conference on Advanced Communication Technology, ICACT | Year: 2014

Single Carrier Frequency Division Multiple Access (SC-FDMA) has been selected for use in the Long Term Evolution (LTE) uplink due to its lower Peak-to-Average Power Ratio (PAPR) relative to OFDMA The resultant lower PAPR results in fewer excursions into the amplifier's nonlinear region, where signal distortion can occur and results in degraded bit error rate (BER). The SC-FDMA scheme normally applies 16-ary Quadrature Amplitude Modulation (16-QAM), but amplitude phase shift keying (APSK) modulation has a lower PAPR than does 16-QAM, resulting in improved BER This paper investigates the constellation ring ratio of the 16-APSK modulation scheme and its effects on BER through its effects on the PAPR. Simulation results are used to conclude that a ring ratio that ranges from 2.5 to 3.5 delivers the best results and provides BER and PAPR improvement. © 2014 Global IT Research Institute (GIRI). Source


Gumfekar S.P.,University of Waterloo | Chen A.,Celestica Inc. | Zhao B.,University of Waterloo
2011 IEEE 13th Electronics Packaging Technology Conference, EPTC 2011 | Year: 2011

Electrical conductive adhesives (ECA) find extensive applications in electronic manufacturing and packaging industries. Compared to the soldering technology, adhesives joining offer numerous advantages including mild processing conditions, fewer processing steps (reducing process cost), and especially, the fine pitch capability due to the availability of small size conductive fillers. ECAs function based on the conductive fillers, typically 1-10μm in size, supported in a polymeric matrix. To be conductive, the loading of fillers needs to be above its percolation threshold - the minimum fraction of fillers needed to establish the conducting network. In this paper, we report a systematic study of percolation thresholds of silver-epoxy (Ag-epoxy) and silver-polyaniline-epoxy (Ag-PANI-epoxy) system. The polyaniline (PANI) has a moderate conductivity in between the silver and epoxy; it was used to dope the epoxy matrix to minimize two problems in the ECAs: (1) localization of charge carriers because of the aggregation of the silver fillers, and (2) the interfacial polarization arising from the intrinsic difference in polarities and surface energies of fillers and epoxy. Two different methods were used to prepare the Ag- PANI -epoxy adhesives. The first method was to add silver fillers into liquid epoxy resin, add PANI, and then the amine hardener. The second method was to add PANI into liquid epoxy resin, add silver fillers, and then the amine hardener. Our experiments showed that silver fillers were well dispersed in cured adhesives prepared in the first method while silver fillers formed aggregates in cured adhesives prepared in second method. We also propose a mechanism of conduction based on surface properties and interactions between fillers and the epoxy matrix. Our results and analysis may help to explain the reduced percolation threshold and enhanced conductivity. © 2011 IEEE. Source


Charest A.,Carleton University | Nakhla M.S.,Carleton University | Achar R.,Carleton University | Saraswat D.,Tyco Electronics | And 2 more authors.
IEEE Transactions on Advanced Packaging | Year: 2010

This paper introduces a new time-domain approach for compact macromodeling of multiport high-speed circuits with long delays, characterized by tabulated data. The algorithm is based on partitioning the data in the time-domain and subsequently, approximating each partition via delayed rational functions. This results in a compact low-order macromodel in the form of delayed differential equations, which can be efficiently analyzed in the time-domain using circuit simulators. © 2006 IEEE. Source


Perovic D.D.,University of Toronto | Snugovsky L.,University of Toronto | Snugovsky P.,Celestica Inc. | Rutter J.W.,University of Toronto
Materials Science and Technology | Year: 2012

In the expectation of a possible connection between Sn-Cu 6Sn 5 and Sn-Zn binary eutectics, several alloy compositions were selected along a possible joining path. Samples of each were solidified unidirectionally at a very slow rate, approximating freezing with complete mixing in the liquid (the 'solidification path' technique). This procedure allows the detection of reactions by the change in the phases frozen out with the change in composition of the liquid due to segregation. Three quasi-peritectic reactions (U1-U3) and a ternary eutectic reaction were found: U1, L+Cu 6Sn 5⇌CuZn+Sn; U2, L+CuZn⇌Cu 5Zn 8+Sn; U3, L+Cu 5Zn 8⇌ CuZn 4+Sn; and E, L⇌(Sn)+(Zn)+CuZn 4. © 2012 Institute of Materials, Minerals and Mining. Source


Gumfekar S.P.,University of Waterloo | Amoli B.M.,University of Waterloo | Chen A.,Celestica Inc. | Zhao B.,University of Waterloo
Journal of Polymer Science, Part B: Polymer Physics | Year: 2013

In this article, the electromechanical properties of silver-in-epoxy conductive adhesives with the polyaniline (PANI) micron particles as cofillers have been investigated. PANI is a conductive polymer and has a moderate conductivity in between those of silver and epoxy. It was found that PANI can be used to tailor both the adhesive's electrical contact resistance and its relaxation behavior; however, the effects of adding PANI were complex. The addition of small amount of PANI (2 wt %) dramatically increased the contact resistance; it might block the electrical contacts among silver flakes and was not able to form a continuous path among themselves. The addition of more PANI showed a moderate increase in contact resistance, which increased with the weight fraction of PANI from 6 to 15 wt %. Interdependent behavior of compressive strain and relaxation in electrical contact resistance is characterized to evaluate the origin of this relaxation. The addition of PANI made the relaxation in electrical contact resistance more sensitive to the compressive strain and the electromechanical coupling to deviate from the linear relationship. These research findings provide insights into the way to use PANI to tailor the electromechanical properties of the adhesive bonds or joints in the development of advanced functional devices. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013, 51, 1448-1455 Electrically conductive adhesives (ECAs) find extensive applications as interconnect materials for device assembly to meet the increasing demand of miniaturization of electronic products and portable devices. However, ECA bonds suffer from a relatively poor reliability in comparison with conventional soldering and wire bonding. In this work, polyaniline is investigated as a cofiller in silver-filled epoxy in both partially cured and fully cured states, providing insights into the establishment of a conductive network and the role of polyaniline in tailoring the electromechanical response of the ECAs. Copyright © 2013 Wiley Periodicals, Inc. Source

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