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Linear Amplification (linear + amplification)

Distribution by Scientific Domains
Engineering60%
Life Sciences40%

Selected Abstracts

Nonlinear signal processing schemes for OFDM modulations within conventional or LINC transmitter structures

EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 3 2008
Rui Dinis
This paper considers two classes of digital signal processing schemes, recently proposed by the authors, both combining a nonlinear operation in the time domain with a linear operation in the frequency domain, so as to reduce the envelope fluctuations and allow good power/bandwidth tradeoffs with Orthogonal Frequency Division Multiplexing (OFDM) transmission. These classes can be adopted within both conventional and two-branch, LInear amplification with Nonlinear Components (LINC) transmitter structures . The paper addresses the statistical characterisation of the transmitted frequency-domain blocks, so as to evaluate performances by analytical means, in a unified manner. A set of numerical results, which have been obtained with the help of this analytical method, is presented and discussed. These results allow a comparison between the two classes of signal processing schemes, namely for nonlinear operations of the ,clipping' type, when a conventional transmitter structure is employed. They also allow an accurate evaluation of the phase and gain imbalance effects in the two-branch power amplification case. Copyright © 2008 John Wiley & Sons, Ltd. [source]

A new impedance match method to improve efficiency of LINC with Chireix combiner

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2010
Tao Ni
Abstract In this article, we propose a new impedance match method in serial Chireix combiner to improve the efficiency of Linear amplification with Nonlinear Components (LINC) amplifier. Based on the impedance characteristics of the serial Chireix combiner, two transmission lines are added between power amplifiers (PAs) and Chireix combiner in LINC. For experimental verification, the PAs and combiner are implemented and tested. From the measured results, this method is proved available for improving efficiency of LINC, and convenient for design as well as tuning work. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1418,1421, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25205 [source]

Amplification of low quantity bacterial RNA for microarray studies: time-course analysis of Leptospirillum ferrooxidans under nitrogen-fixing conditions,

ENVIRONMENTAL MICROBIOLOGY, Issue 6 2006
Mercedes Moreno-Paz
Summary We have developed a method for the amplification of low quantity total bacterial RNA for DNA microarrays analysis. Current methods are based on the linear amplification by the in vitro transcription from the T7 promoter, similar to that used for eukaryotic mRNA amplification. For the incorporation of T7 promoter, the prokaryotic RNA must be enzymatically modified for the incorporation of a polyA tail at the 3, end to emulate the eukaryotic mRNA. The method we describe and validate herein avoids this step by the direct and random incorporation of the T7 promoter. From 500 ng of total bacterial RNA, we obtained 130,150 µg of antisense RNA, such products being good substrate for fluorescent labelling and DNA microarray analysis. The method was validated with bacterial samples from which it is very difficult to obtain sufficient amounts and quality of total RNA for global gene expression analysis. This is critical for low cell density growing microorganisms, environmental samples, or many extremophiles where the composition of the cultural media severely affects the RNA yield, like in the case of the acidophile and iron oxidizer Gram-negative bacterium Leptospirillum ferrooxidans. We further validated our amplification method in parallel experiments with non-amplified RNA by following the expression of the L. ferrooxidans nif regulon along the time-course of growth. [source]

Linear allele-specific long-range amplification: a novel method of long-range molecular haplotyping,,

HUMAN MUTATION, Issue 4 2005
Wei-Ming Wu
Abstract Haplotypes have been repeatedly shown to be more powerful than collections of single-locus markers in gene-mapping studies. Various haplotyping methods including statistical estimation are employed but molecular haplotyping, the acquisition of information directly on physical DNA sequences, has been in demand for its accuracy and independence from family pedigrees. We investigated the allelic specificity of long-range PCR, which was successful for long-range haplotyping in recent reports, and found problems of initial mispriming and crossover amplification significantly confounded its application. Based on these observations, we designed a novel method based on linear amplification of a hemizygous DNA segment with a single phosphorothioate-modified oligonucleotide. Our results revealed, with a single nucleotide polymorphism as the discriminative marker, downstream haplotypes of 14,15 kb DNA segment could be confidently scored. With two rounds of the method and five single nucleotide polymorphisms, molecular haplotypes of 29.3 kb spanning the HCR and CDSN genes, two genes associated with the susceptibility of psoriasis, of 11 members, belonging to a CEPH family, were revealed. Clear Mendelian segregation of 35 highly heterozygous SNPs confirmed the accuracy of the method. Problems of low specificity associated with long-range PCR were not observed. The simplicity, along with long-sequence accessibility and feasibility of a single nucleotide difference as the discriminative marker indicated our method holds promise for future gene-mapping studies. © 2005 Wiley-Liss, Inc. [source]

Gain-assisted metamaterial embedded with gain elements

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2010
Tao Jiang
Abstract In this letter, an active metamaterial sample embedded with miniature monolithic microwave amplifiers is designed, experimentally realized, and measured. Experiments show that by proper design and direct current (DC) bias, the metamaterial sample provides almost linear amplification to an electromagnetic incidence, which can be used to compensate the loss inherent in traditional passive metamaterial and magnify the signal entered the metamaterial. This property would have important potentials in promoting the further researches of metamaterial-based applications. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 92,95, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24871 [source]