A great interest has been gained in recent years by a new error-correcting code technique, known as "turbo coding," which has been proven to offer performance closer to the Shannon's limit than traditional concatenated codes. In this paper, several very large scale integration (VLSI) architectures suitable for turbo decoder implementation are proposed and compared in terms of complexity and performance; the impact on the VLSI complexity of system parameters like the state number, number of iterations, and code rate are evaluated for the different solutions. The results of this architectural study have then been exploited for the design of a specific decoder, implementing a serial concatenation scheme with 2/3 and 3/4 codes; the designed circuit occupies 35 mm 2 , supports a 2-Mb/s data rate, and for a bit error probability of 10 06 , yields a coding gain larger than 7 dB, with ten iterations.
Molecular Quantum Dot Cellular Automata, also called mQCA, are among the most promising emerging technologies for the expected theoretical operating frequencies (THz), the high device densities and the non-cryogenic working temperature. Due to the small size of a mQCA cell, based on one or two molecules, the device prototyping and even a simple circuit fabrication are limited by the lack of control in the technological process. In this paper, we performed an analysis of the possible fabrication defects of a molecular QCA wire built with adhoc synthesized bis-ferrocene molecules. We evaluated the fault tolerance of a real QCA device and accessed its performance in non ideal conditions due to the fabrication criticalities we are facing in our experiments. We achieved these results by defining a new methodology for the fault analysis in the mQCA technology, based both on ab-initio simulations and theoretical computations.The results obtained give quantitative information on the Safe-Operating-Area (SOA) of a bisferrocene molecular wire, and represent an important feedback to improve the technological process for the final experimental set-up.
This study is focused on the realization of nanodevices for nano and molecular electronics, based on molecular interactions in a metal-molecule-metal (M-M-M) structure. In an M-M-M system, the electronic function is a property of the structure and can be characterized through I/V measurements. The contact between the metals and the molecule was obtained by gold nanogaps (with a dimension of less than 10 nm), produced with the electromigration technique. The nanogap fabrication was controlled by a custom hardware and the related software system. The studies were carried out through experiments and simulations of organic molecules, in particular oligothiophenes.
The electrical conductance response of single ZnO microwire functionalized with amine-groups was tested upon an acid pH variation of a solution environment after integration on a customized gold electrode array chip. ZnO microwires were easily synthesized by hydrothermal route and chemically functionalized with aminopropyl groups. Single wires were deposited from the solution and then oriented through dielectrophoresis across eight nanogap gold electrodes on a platform single chip. Therefore, eight functionalized ZnO microwire-gold junctions were formed at the same time, and being integrated on an ad hoc electronic platform, they were ready for testing without any further treatment. Experimental and simulation studies confirmed the high pH-responsive behavior of the amine-modified ZnO-gold junctions, obtaining in a simple and reproducible way a ready-to-use device for pH detection in the acidic range. We also compared this performance to bare ZnO wires on the same electronic platform, showing the superiority in pH response of the amine-functionalized material.
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