196,663 research outputs found
A 24GHz Sub-Harmonic Receiver Front-End with Integrated Multi-Phase LO Generation in 65nm CMOS
No full textA sub-harmonic architecture for wireless signal processing at Ka band is proposed resulting in IC power saving because the LO circuits operate at half frequency and no IF stage is necessary. A 65nm CMOS prototype, including High Frequency front-end, base-band amplifier and multi-phase VCO and dividers, shows: 31.5dB gain, 6.5dB NF, -17dBm IIP3, -90dBm LO re-irradiation at 24GHz, while consuming 92mW
CMOS injection locked oscillators for quadrature generation at radio-frequency
No full textThe design of quadrature local oscillators for CMOS wireless transceivers is still one of the most challenging issues. This paper focuses the advantages of injection locking techniques to achieve high-performance quadrature generators. A synchronizing oscillator sets spectral purity while locked oscillators set quadrature accuracy and drive the mixer LO input capacitances. Two different architectures, realized in a 0.18 mu m CMOS technology, are illustrated and compared. The first, using LC tank locked oscillators as frequency dividers, is tailored to UNITS and show high driving capability with low power. Simple and accurate equations for the design are reported. The second quadrature generator, employing coupled VCOs driven by an auxiliary VCO, is tailored to DCS1800 and achieves outstanding phase accuracy and phase noise. Experimental results compare favorably against previously published solutions. (c) 2006 Elsevier Ltd. All rights reserved
A 1.8-GHz Injection-Locked Quadrature CMOS VCO With Low Phase Noise and High Phase Accuracy
No full textInjection-locked quadrature voltage-controlled oscillators are introduced in this paper as high accuracy, low phase noise, and low-power I and Q generators. A master voltage-controlled osciflator (VCO), running at twice the output frequency, locks two coupled VCOs. The former determines phase noise while the latter sets phase accuracy, thus, breaking the tradeoff between the two parameters, the main limit of free running coupled VCOs, recently proposed in the framework of highly integrated solutions. The proposed design has been tailored to DCS 1800 and prototypes have been fabricated in a 0.18-mu m CMOS technology. Experiments show a phase noise of -127 dBc/Hz and -139 dBc/Hz at 600 kHz and 3 MHz, respectively, while consuming 10 mA from 1.8 V supply. A 185-dB state-of-the-art phase noise figure of merit results. Accuracy between output signals is determined by means of image band rejection (HIR) measurements on a purposely developed single-side-band upconversion mixer. Minimum IBR among 20 samples is as large as 46 dB
Polarized traffic towards the cell surface: how to find the route
No full textAbstract: Polarity is the structural and functional hallmark of epithelia. The apical plasma membrane, facing the organism's exterior (the lumen of the gut, renal tubule and glandular duct), differs in many important respects from the basolateral plasma membrane that is apposed to the interior of the organism. The generation and maintenance of epithelial polarity require a highly specialized subcellular machinery to bring proteins to their appropriate sites of action. This is a dynamic process involving the interpretation of sorting signals, vectorial delivery mechanisms, membrane-specific fusion and retention processes. Here, we will provide a review of the field, highlighting recent advances within a historically relevant context
A CMOS Sub-Harmonic Architecture for Signal Down-Converion at Ka-Band
No full textQuadrature Sub-Harmonic mixing to DC or low-IF can be attractive for signal processing at Ka-band. Frequency translation is performed without the need for a local oscillator at the received signal frequency. A lower frequency reference takes advantage of the higher quality of tuning elements and avoids high frequency, powerhungry dividers in the synthesizer. Moreover DC offsetand second-order inter-modulation distortion, due to poor LO-RF isolation, are mitigated by the LO running at lower frequency. This paper presents the receiver IC architecture and experiments from a quadrature demodulator realized in 65nm CMOS
Amplitude and frequency stabilized solid-state lasers in the near infrared
No full textIn this article we present a comprehensive review of the work done by our group on the amplitude and frequency stabilization of diode-pumped near-infrared solid-state lasers. In particular, we describe experiments based on single-mode Nd:YAG (1064 nm), Er-Yb:glass (1530-1560 nm), and Tm-Ho:YAG (2097 nm) lasers, end-pumped by semiconductor laser diodes. Amplitude stabilization is achieved by means of optoelectronic control loops sensing the laser intensity fluctuations and feeding back the error signal to the current of the pump diodes. Frequency stabilization is pursued using rovibrational molecular lines as absolute frequency references by means of various frequency locking techniques. The most interesting stability results are described in some detail whereas the wide literature cited through the paper provides for a useful reference list of related topics and experiments
Gallbladder histopathology during murine gallstone formation: relation to motility and concentrating function
No full textC57L mice are susceptible and AKR mice are
resistant to gallstone formation. We studied in male mice
of both strains gallbladder histopathology, cholecystokinininduced
emptying, and concentrating function at 0, 14, 28,
and 56 days on a lithogenic diet. Gallbladder wall thickness
increased on the diet, with stromal granulocyte infiltration,
progressive fibrosis, edema, and epithelial cell
indentation, particularly in C57L. Strong basal cholecystokinin
octapeptide-induced gallbladder emptying (70% of
fasting volumes) occurred in both strains, but fasting gallbladder
volumes were significantly larger in C57L (14.8 6
2.2 ml vs. 8.8 6 1.0 ml). On the diet, fasting volumes increased
exclusively in C57L (28.6 6 2.9 ml on day 56), with
progressively decreased emptying (27% of fasting volumes
on day 56). Gallbladder emptying remained normal in
AKR. Gallbladder concentrating function decreased on the
lithogenic diet (especially in C57L), coinciding with decreased
aquaporin-1 (AQP1) and AQP8 expression at the
mRNA and protein levels. In additional experiments, similar
downregulation of AQP1 and AQP8 mRNA expression occurred
in farnesoid X receptor (FXR)-deficient mice after
1 week on the lithogenic diet, without any difference from
corresponding wild-type mice. In conclusion, during murine
lithogenesis, altered gallbladder histology is associated with
impaired motility, reduced concentrating function, and decreased
AQP1 and AQP8 expression, the latter without the
involvement of the FXR.—van Erpecum, K. J., D.Q-H.Wang,
A.Moschetta,D. Ferri, M. Svelto, P. Portincasa, J-J. Hendrickx,
M. Schipper, and G. Calamita. Gallbladder histopathology
during murine gallstone formation: relation to motility and
concentrating function
Na+-K+-2Cl- cotransporter type 2 trafficking and activity: The role of interacting proteins
No full textThe central role of Na+–K+–2Cl− cotransporter type 2 (NKCC2) in vectorial transepithelial salt reabsorption in
thick ascending limb cells from Henle’s loop in the kidney is evidenced by the effects of loop diuretics, the
pharmacological inhibitors of NKCC2, that are amongst the most powerful antihypertensive drugs available to
date. Moreover, genetic mutations of the NKCC2 encoding gene resulting in impaired apical targeting and function
of NKCC2 transporter give rise to a pathological phenotype known as type I Bartter syndrome, characterised by
a severe volume depletion, hypokalaemia and metabolic alkalosis with high prenatal mortality. On the contrary,
excessive NKCC2 activity has been linkedwith inherited hypertension in humans and in rodent models. Interestingly,
in animal models of hypertension, NKCC2 upregulation is achieved by post-translational mechanisms underlining
the need to analyse the molecular mechanisms involved in the regulation of NKCC2 trafficking and activity to gain insights in the pathogenesis of hypertension
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