10 research outputs found
Analog integrated circuit design techniques for high-speed signal processing in communications systems
This work presents design techniques for the implementation of high-speed analog
integrated circuits for wireless and wireline communications systems.
Limitations commonly found in high-speed switched-capacitor (SC) circuits used
for intermediate frequency (IF) filters in wireless receivers are explored. A model
to analyze the aliasing effects due to periodical non-uniform individual sampling,
a technique used in high-Q high-speed SC filters, is presented along with practical
expressions that estimate the power of the generated alias components. The results
are verified through circuit simulation of a 10.7MHz bandpass SC filter in TSMC
0.35mu-m CMOS technology. Implications on the use of this technique on the design of
IF filters are discussed.
To improve the speed at which SC networks can operate, a continuous-time
common-mode feedback (CMFB) with reduced loading capacitance is proposed. This
increases the achievable gain-bandwidth product (GBW) of fully-differential ampli-
fiers. The performance of the CMFB is demonstrated in the implementation of a
second-order 10.7MHz bandpass SC filter and compared with that of an identical
filter using the conventional switched-capacitor CMFB (SC-CMFB). The filter using
the continuous-time CMFB reduces the error due to finite GBW and slew rate to less
than 1% for clock frequencies up to 72MHz while providing a dynamic range of 59dB and a PSRR- > 22dB. The design of high-speed transversal equalizers for wireline transceivers requires the implementation of broadband delay lines. A delay line based on a third-order
linear-phase filter is presented for the implementation of a fractionally-spaced 1Gb/s
transversal equalizer. Two topologies for a broadband summing node which enable
the placement of the parasitic poles at the output of the transversal equalizer beyond
650MHz are presented. Using these cells, a 5-tap 1Gb/s equalizer was implemented
in TSMC 0.35mu-m CMOS technology. The results show a programmable frequency
response able to compensate up to 25dB loss at 500MHz. The eye-pattern diagrams
at 1Gb/s demonstrate the equalization of 15 meters and 23 meters of CAT5e twistedpair
cable, with a vertical eye-opening improvement from 0% (before the equalizer)
to 58% (after the equalizer) in the second case. The equalizer consumes 96mW and
an area of 630mu-m x 490mu-m
Diversity of Mycobacterium tuberculosis genotypes circulating in Ndola, Zambia
<p>Abstract</p> <p>Background</p> <p>Tuberculosis (TB) is one of the major public health problems in Zambia. However, information about lineages of <it>M. tuberculosis </it>complex (MTBC) isolates useful for epidemiology investigations is unknown. In this study, we investigated the diversity of MTBC isolates from Ndola, a typical Zambian urbanized city with a documented high HIV prevalence.</p> <p>Methods</p> <p>This was part of a prospective cohort study in subjects with sputum smear-positive pulmonary TB. Spoligotyping was used to genotype the MTBC isolates and establish the circulating lineages. The 15-locus Mycobacterial Interspersed Repetitive Units - Variable Number Tandem Repeats (MIRU-VNTR) typing was used to study recent transmission.</p> <p>Results</p> <p>A total of 98 different spoligotypes were identified among 273 MTBC isolates. The majority (64.8%) of the isolates belonged to 9 known families, while 96 (35.2%) of the isolates were orphans. While LAM (41.8%) was the largest spoligotype family observed, most of the isolates (87.7%) belonging to the SAF1 family, with a significant portion coming from the T (13.6%), and X (5.9%) families. A few isolates (3.6%) belonged to the CAS, EAI, H, S, X1-LAM9 or U families. MIRU-VNTR typing was highly discriminatory (h = 0.988) among the 156 isolates tested in our sample, and increased the discrimination among 82 SAF1 isolates from 6 to 46 distinct patterns. In addition, 3.2% (5/156) of cases with available MIRU-VNTR results harbored more than one MTBC strain.</p> <p>Conclusions</p> <p>Our findings show a limited diversity of MTBC in Ndola with a high clustering rate (37.7%), which indicates that recent transmission plays an appreciable role in the dynamics of TB disease in this setting. This conclusion emphasizes the importance of early diagnosis and timely treatment. The results also confirm that MIRU-VNTR typing is suitable for studying the molecular epidemiology of TB in Ndola.</p
Finishing the euchromatic sequence of the human genome
The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers âŒ99% of the euchromatic genome and is accurate to an error rate of âŒ1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead
DigitalizaciĂłn y EnergĂa Solar
ste informe del Grupo de Trabajo de DigitalizaciĂłn y EnergĂa Solar de SolarPower Europe y ASOLMEX es el primero que analiza especĂficamente la intersecciĂłn de la energĂa solar fotovoltaica y la digitalizaciĂłn en MĂ©xico, y evalĂșa la manera en la que se puede aplicar la nueva tecnologĂa digital a la energĂa solar. Su intenciĂłn es abordar de quĂ© manera el mercado fotovoltaico puede aprovechar al mĂĄximo las oportunidades de digitalizaciĂłn y cĂłmo esta puede ser un motor para un mayor despliegue de la energĂa solar
Fluctuation Analysis of Tetanic Rundown (Short-Term Depression) at a Corticothalamic Synapse
Hypothetical scenarios for âtetanic rundownâ (âshort-term depressionâ) of synaptic signals evoked by stimulus trains differ in evolution of quantal amplitude (Q) and covariances between signals. With corticothalamic excitatory postsynaptic currents (EPSCs) evoked by 2.5- to 20-Hz trains, we found Q (estimated using various corrections of variance/mean ratios) to be unchanged during rundown and close to the size of stimulus-evoked âminiaturesâ. Except for covariances, results were compatible with a depletion model, according to which incomplete ârefillâ after probabilistic quantal release entails release-site âemptyingâ. For five neurons with 20 train repetitions at each frequency, there was little between-neuron variation of rundown; pool-refill rate increased with stimulus frequency and evolved during rundown. Covariances did not fit the depletion model or theoretical alternatives, being excessively negative for adjacent EPSCs early in trains, absent at equilibrium, and anomalously positive for some nonadjacent EPSCs. The anomalous covariances were unaltered during pharmacological blockade of receptor desensitization and saturation. These findings suggest that pool-refill rate and release probability at each release site are continually modulated by antecedent outputs in its neighborhood, possibly via feedback mechanisms. In all data sets, sampling errors for between-train variances were much less than theoretical, warranting reconsideration of the probabilistic nature of quantal transmitter release