The article demonstrates a novel Digital Predistortion (DPD) architecture for Mobile Front Haul links for the advanced Long-Term Evolution (LTE) and upcoming 5G networks. Precisely, the use of a ...feedback approximation method has been proposed and experimentally demonstrated herein that simplifies the complexities in realizing the practical DPD technique for Multi-Mode VCSELs and Multi-Mode Fibers based Radio over Fiber systems. As a figure of merit, linearization efficiency is provided in terms of Adjacent Channel Power Ratio, Normalized Mean Square Error and Error Vector Magnitude referring to a complete LTE frame occupying 10 MHz with 256-QAM modulation format.
To decrease cost and consumption of future wireless infrastructures, radio-over fibre systems utilising 850 nm vertical cavity surface emitting lasers and standard single-mode fibre (SSMF) are ...deserving particular attention in replacing the typical use of graded-index multimode fibre (GI-MMF). In the present work, a characterisation of noise and non-linearities of these links is performed, followed by an estimation of their impact on the system dynamics and the quality of the received signal. This allows to show that very good and similar performances can be obtained through the utilisation of SSMF and GI-MMF for the transmission of five long-term evolution channels with 20 MHz bandwidth, confirming that the former, by the higher diffusion and lower cost per metre of the SSMF, can be put among the leading candidates for the realisation of fourth-generation (4G) and 5G wireless networks.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
This Letter presents the impact of silicon substrate resistivity on SiGe phototransistors. SiGe phototransistors were fabricated on the commercially available SiGe/Si bipolar technology. The ...performances of the phototransistors fabricated based on low- and the high-resistive silicon substrate are compared. The phototransistor based on low-resistivity (LR) silicon substrate provides a responsivity of more than double compared to the phototransistor based on a high-resistivity silicon substrate that is fabricated by using the same bipolar transistor technology. The phototransistor fabricated on LR substrate exhibits low-frequency responsivity up to 1.35 A/W (at 50 MHz).
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
This paper describes two small aperture array demonstrators called Medicina and Sardinia Array Demonstrators (MAD and SAD, respectively). The objectives of these instruments are to acquire experience ...and test new technologies for a possible application to the low‐frequency aperture array of the low‐frequency telescope of the Square Kilometer Array phase 1 (SKA1‐LOW). The MAD experience was concluded in 2014, and it turned out to be an important test bench for implementing calibration techniques based on an artificial source mounted in an aerial vehicle. SAD is based on 128 dual‐polarized Vivaldi antennas and is 1 order of magnitude larger than MAD. The architecture and the station size of SAD, which is along the construction phase, are more similar to those under evaluation for SKA1‐LOW, and therefore, SAD is expected to provide useful hints for SKA1‐LOW.
Key Points
Italian demonstrators of low‐frequency aperture array for radio astronomy
Aerial unmanned vehicle for the instrumental calibration of an aperture array
Technological solutions implemented in the receiving chain of a low‐frequency aperture array
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
A comprehensive theoretical and experimental investigation is presented on the performances of cost-effective radio over fiber (RoF) links where the RoF Transmitter is directly modulated by signals ...complying the Universal Mobile Telecommunications Service (UMTS) and Worldwide Interoperability for Microwave Access (WiMAX) standards. A numerical model for calculating intermodulation related quantities like the adjacent channel leakage ratio has been developed for this purpose. Measurements have also been performed over real RoF Systems modulated by UMTS and WiMAX signals. A very good agreement has been found between measured and modelled results, and the feasibility of these connections over distances of tens of kilometers has been investigated.
The characteristics of triangular photonic crystal fibers (PCFs) with elliptical holes filled with a nematic liquid crystal (LC) are investigated theoretically. The analysis that is carried out using ...the finite-element method, including material dispersion effects, shows that LC anisotropy and hole ellipticity allow some phenomena that are not predicted yet, such as polarization-dependent losses and birefringence sign change in the wavelength range used for standard telecom fibers. Control of these features allows the design of new devices for sensing or telecommunication applications.
The design and development process for the Square Kilometre Array (SKA) radio telescope’s Low Frequency Aperture Array component was progressed during the SKA pre-construction phase by an ...international consortium, with the goal of meeting requirements for a critical design review. As part of the development process a full-sized prototype SKA Low ‘station’ was deployed – the Aperture Array Verification System 1 (AAVS1). We provide a system overview and describe the commissioning results of AAVS1, which is a low frequency radio telescope with 256 dual-polarisation log-periodic dipole antennas working as a phased array. A detailed system description is provided, including an in-depth overview of relevant sub-systems, ranging from hardware, firmware, software, calibration, and control sub-systems. Early commissioning results cover initial bootstrapping, array calibration, stability testing, beam-forming, and on-sky sensitivity validation. Lessons learned are presented, along with future developments.
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FMFMET, NUK, UL, UM, UPUK
Angiotensin-converting–enzyme (ACE) inhibitors improve outcomes in patients with left ventricular dysfunction or heart failure. The Prevention of Events with Angiotensin Converting Enzyme Inhibition ...(PEACE) Trial investigators studied the effect of the ACE inhibitor trandolapril in patients with stable coronary disease and normal or only slightly reduced left ventricular function, and no benefit was found.
This trial appears to define the limits of efficacy of ACE inhibition in patients who are already receiving maximal contemporary therapy.
Blockade of the renin–angiotensin system has been shown to prolong survival and reduce adverse outcomes in patients with systolic heart failure
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or left ventricular systolic dysfunction.
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Indeed, angiotensin-converting–enzyme (ACE) inhibitors have become a cornerstone in the treatment of these patients.
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In addition, post hoc analyses of patients from the Studies of Left Ventricular Dysfunction (SOLVD)
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and the Survival and Ventricular Enlargement (SAVE) trials,
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both randomized studies that involved patients with moderate-to-severe left ventricular dysfunction, showed a reduction in the rate of acute myocardial infarction in patients who were treated with an ACE inhibitor. These observations raised . . .
It is known that the angiotensin-converting–enzyme inhibitor captopril is beneficial in patients with myocardial infarction complicated by left ventricular dysfunction or heart failure. This study ...compared captopril with valsartan, an angiotensin-receptor blocker, and the combination of the two drugs in such patients. Mortality was the same in the three groups, but there were more side effects with the combination therapy.
In patients with heart failure, valsartan is an alternative.
Multiple randomized, placebo-controlled trials involving a total of more than 100,000 patients have demonstrated that angiotensin-converting–enzyme (ACE) inhibitors reduce the risk of death as well as the risk of major nonfatal cardiovascular events after myocardial infarction.
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The greatest relative and absolute benefits have been obtained with long-term ACE-inhibitor therapy in high-risk patients — specifically, in those with left ventricular dysfunction, signs or symptoms of heart failure, or both.
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Angiotensin-receptor blockers offer an alternative approach to the inhibition of the renin–angiotensin system.
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The identification of a functioning chymase in humans that is capable of generating angiotensin II independently of . . .
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