11,291 research outputs found
High Dynamic Range RF Front End with Noise Cancellation and Linearization for WiMAX Receivers
This research deals with verification of the high dynamic range for a heterodyne radio frequency (RF) front end. A 2.6 GHz RF front end is designed and implemented in a hybrid microwave integrated circuit (HMIC) for worldwide interoperability for microwave access (WiMAX) receivers. The heterodyne RF front end consists of a low-noise amplifier (LNA) with noise cancellation, an RF bandpass filter (BPF), a downconverter with linearization, and an intermediate frequency (IF) BPF. A noise canceling technique used in the low-noise amplifier eliminates a thermal noise and then reduces the noise figure (NF) of the RF front end by 0.9 dB. Use of a downconverter with diode linearizer also compensates for gain compression, which increases the input-referred third-order intercept point (IIP3) of the RF front end by 4.3 dB. The proposed method substantially increases the spurious-free dynamic range (DRf) of the RF front end by 3.5 dB
A 0.8 V T Network-Based 2.6 GHz Downconverter RFIC
A 2.6 GHz downconverter RFIC is designed and implemented using a 0.18 μm CMOS standard process. An important goal of the design is to achieve the high linearity that is required in WiMAX systems with a low supply voltage. A passive T phase-shift network is used as an RF input stage in a Gilbert cell to reduce supply voltage. A single supply voltage of 0.8 V is used with a power consumption of 5.87 mW. The T network-based downconverter achieves a conversion gain (CG) of 5 dB, a single-sideband noise figure (NF) of 16.16 dB, an RF-to-IF isolation of greater than 20 dB, and an input-referred third-order intercept point (IIP3) of 1 dBm when the LO power of -13 dBm is applied
Model reconstructions for the Si(337) orientation
Although unstable, the Si(337) orientation has been known to appear in
diverse experimental situations such as the nanoscale faceting of Si(112), or
in the case of miscutting a Si(113) surface. Various models for Si(337) have
been proposed over time, which motivates a comprehensive study of the structure
of this orientation. Such a study is undertaken in this article, where we
report the results of a genetic algorithm optimization of the Si(337)- surface. The algorithm is coupled with a highly optimized empirical
potential for silicon, which is used as an efficient way to build a set of
possible Si(337) models; these structures are subsequently relaxed at the level
of ab initio density functional methods. Using this procedure, we retrieve most
of the (337) reconstructions proposed in previous works, as well as a number of
novel ones.Comment: 5 figures (low res.); to appear in J. Appl. Phy
Fast Shocks From Magnetic Reconnection Outflows
Magnetic reconnection is commonly perceived to drive flow and particle
acceleration in flares of solar, stellar, and astrophysical disk coronae but
the relative roles of different acceleration mecha- nisms in a given
reconnection environment are not well understood. We show via direct numerical
simulations that reconnection outflows produce weak fast shocks, when
conditions for fast recon- nection are met and the outflows encounter an
obstacle. The associated compression ratios lead to a Fermi acceleration
particle spectrum that is significantly steeper than the strong fast shocks
commonly studied, but consistent with the demands of solar flares. While this
is not the only acceleration mechanism operating in a reconnection environment,
it is plausibly a ubiquitous one
Molecular Markers in Cutaneous Squamous Cell Carcinoma
Nonmelanoma skin carcinoma (NMSC) is the most frequent cancer in the USA with over 1.3 million new diagnoses a year; however due to an underappreciation of its associated mortality and growing incidence and its ability to be highly aggressive, the molecular mechanism is not well delineated. Whereas the molecular profiles of melanoma have been well characterized, those for cutaneous squamous cell carcinoma (cSCC) have trailed behind. This importance of the new staging paradigm is linked to the ability currently to better clinically cluster similar biologic behavior in order to risk-stratify lesions and patients. In this paper we discuss the trends in NMSC and the etiologies for the subset of NMSC with the most mortality, cutaneous SCC, as well as where the field stands in the discovery of a molecular profile. The molecular markers are highlighted to demonstrate the recent advances in cSCC
Fast Quantum Search Algorithms in Protein Sequence Comparison - Quantum Biocomputing
Quantum search algorithms are considered in the context of protein sequence
comparison in biocomputing. Given a sample protein sequence of length m (i.e m
residues), the problem considered is to find an optimal match in a large
database containing N residues. Initially, Grover's quantum search algorithm is
applied to a simple illustrative case - namely where the database forms a
complete set of states over the 2^m basis states of a m qubit register, and
thus is known to contain the exact sequence of interest. This example
demonstrates explicitly the typical O(sqrt{N}) speedup on the classical O(N)
requirements. An algorithm is then presented for the (more realistic) case
where the database may contain repeat sequences, and may not necessarily
contain an exact match to the sample sequence. In terms of minimizing the
Hamming distance between the sample sequence and the database subsequences the
algorithm finds an optimal alignment, in O(sqrt{N}) steps, by employing an
extension of Grover's algorithm, due to Boyer, Brassard, Hoyer and Tapp for the
case when the number of matches is not a priori known.Comment: LaTeX, 5 page
Assembling large, complex environmental metagenomes
The large volumes of sequencing data required to sample complex environments
deeply pose new challenges to sequence analysis approaches. De novo metagenomic
assembly effectively reduces the total amount of data to be analyzed but
requires significant computational resources. We apply two pre-assembly
filtering approaches, digital normalization and partitioning, to make large
metagenome assemblies more comput\ ationaly tractable. Using a human gut mock
community dataset, we demonstrate that these methods result in assemblies
nearly identical to assemblies from unprocessed data. We then assemble two
large soil metagenomes from matched Iowa corn and native prairie soils. The
predicted functional content and phylogenetic origin of the assembled contigs
indicate significant taxonomic differences despite similar function. The
assembly strategies presented are generic and can be extended to any
metagenome; full source code is freely available under a BSD license.Comment: Includes supporting informatio
Quantum information and precision measurement
We describe some applications of quantum information theory to the analysis
of quantum limits on measurement sensitivity. A measurement of a weak force
acting on a quantum system is a determination of a classical parameter
appearing in the master equation that governs the evolution of the system;
limitations on measurement accuracy arise because it is not possible to
distinguish perfectly among the different possible values of this parameter.
Tools developed in the study of quantum information and computation can be
exploited to improve the precision of physics experiments; examples include
superdense coding, fast database search, and the quantum Fourier transform.Comment: 13 pages, 1 figure, proof of conjecture adde
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