Low Power Implementation of Non Power-of-Two FFTs on Coarse-Grain Reconfigurable Architectures

The DRM standard for digital radio broadcast in the AM band requires integrated devices for radio receivers at very low power. A System on Chip (SoC) call DiMITRI was developed based on a dual ARM9 RISC core architecture. Analyses showed that most computation power is used in the Coded Orthogonal Frequency Division Multiplexing (COFDM) demodulation to compute Fast Fourier Transforms (FFT) and inverse transforms (IFFT) on complex samples. These FFTs have to be computed on non power-of-two numbers of samples, which is very uncommon in the signal processing world. The results obtained with this chip, lead to the objective to decrease the power dissipated by the COFDM demodulation part using a coarse-grain reconfigurable structure as a coprocessor. This paper introduces two different coarse-grain architectures: PACT XPP technology and the Montium, developed by the University of Twente, and presents the implementation of a\ud Fast Fourier Transform on 1920 complex samples. The implementation result on the Montium shows a saving of a factor 35 in terms of processing time, and 14 in terms of power consumption compared to the RISC implementation, and a\ud smaller area. Then, as a conclusion, the paper presents the next steps of the development and some development issues

Inducible nitric oxide synthase in human diseases

To improve power figures of a dual ARM9 RISC core architecture targeting low-power digital broadcasting applications, the addition of a coarse-grain architecture is considered. This paper introduces two of these structures: PACT's XPP technology and the Montium, developed by the University of Twente, and presents the implementation of a Fast Fourier Transform on 1920 complex samples on both of them. Results in terms of processing time, resource utilization and energy dissipation are described and compared to those we have obtained on the RISC core. Then, as a conclusion, the paper presents the next steps of the development and some development issues

Is there a photostable conjugated polymer for efficient solar cells?

International audienceThe preservation of organic polymer solar cell (PSC) performances over time is of significant concern for their commercial development. A prime PSC degradation pathway is due to inherently photo-unstable conjugated polymers in the photo-active layer which bear continuous illumination in the presence of atmospheric oxygen that diffuses across the encapsulation layers to the whole device. This paper reports on the unexpected photostability of a low band gap polymer, namely poly[(benzo[1,2-b:4,5-b′]dithiophene)-alt-(thieno[3,4-c]pyrrole-4,6-dione)] (PBDTTPD), designed for efficient bulk heterojunction PSCs. An approach based on joint computational and spectroscopic studies is implemented to explain the unexpectedly high resistance of PBDTTPD towards photo-oxidation. It is shown that alkoxy side-chains on benzo[1,2-b;3,4-b]dithiophene (BDT) subunits mitigate the photodegradation of the whole polymer. Furthermore, PBDTTPD favours well-organized structures which inhibit the propagation of the chain oxidation process. Last but not least, results suggest that PBDTTPD is a self-protecting polymer. The first main highlight of this study is that the structure-photostability relationship of conjugated polymers can be dependent on both the macromolecular structure and the morphology of the polymer deposits. The second highlight is that the choice of solubilizing side-chains is a critical factor in the design of stable conjugated polymers for efficient PSCs