Sylloge Fungorum Omnium Hucusque Cognitorum : Vol. XIX. Index iconum fungorum

Sylloge Fungorum Omnium Hucusque Cognitorum es una importante obra micológica que consta de 26 volúmenes compilada por Pier Andrea Saccardo (1845-1920), quien fuera un micólogo y botánico italiano. Esta importante obra de taxonomía de hongos (escrita entre 1882 y 1890) es una lista con todos los nombres científicos utilizados y una breve descripción de los hongos. Estas descripciones siguen siendo referencias para los taxónomos actuales. Esta importante colección se encuentra depositada en el Instituto Spegazzini gracias a la generosa donación que hiciera el principal discípulo de Saccardo, el Dr. Carlos Spegazzini, y constituye la única colección de su tipo disponible en América del Sur.Material digitalizado en SEDICI gracias a la colaboración del Instituto de Botánica "Dr. Carlos Spegazzini" (Facultad de Ciencias Naturales y Museo, UNLP).Instituto de Botánica "Dr. Carlos Spegazzini

Low-frequency noise measurements in silicon power MOSFETs as a tool to experimentally investigate the defectiveness of the gate oxide

Peer Reviewe

A nonlinear dynamic S/H-ADC device model based on a modified Volterra series: identification procedure and commercial CAD tool implementation

A nonlinear, dynamic empirical model, based on a Volterra-like approach, was previously proposed by the authors for the time-oriented characterization of sample/hold (S/H) and analog-to-digital conversion (ADC) devices. In this paper, the experimental procedure for model parameter measurement is presented, as well as techniques devoted to the implementation of the model in the framework of the main commercial CAD tools for circuit analysis and design. Examples of simulations, performed both in the time and frequency domain on the model obtained for a commercial device, are proposed, which show the model's capability of pointing out the dynamic nonlinear effects in the S/H-ADC response

Experimental characterization of Sigma Delta Radio over fiber system for 5G C-RAN downlink

Radio over Fiber is a promising technology for the 5G Cloud Radio Access Network. We demonstrate experimentally Sigma Delta Radio over Fiber by means of Sigma Delta Modulator (SDM) subsequently replacing expensive digital to analog converters. A second order SDM is proposed for LTE 20 MHz signal having 256 QAM modulation on a carrier frequency of 3.5 GHz for 10 Km of fiber length. The performance is reported in terms of error vector magnitude, adjacent channel leakage ratio and eye-opening penalty. The results show that the proposed architecture performance is cost and power efficient solution for next-generation wireless networks. Keywords: Radio over fiber, Sigma delta modulation, 5G C-RAN, EVM, ACP

Sylloge Fungorum Omnium Hucusque Cognitorum : Vol. XX. Index iconum fungorum

Sylloge Fungorum Omnium Hucusque Cognitorum es una importante obra micológica que consta de 26 volúmenes compilada por Pier Andrea Saccardo (1845-1920), quien fuera un micólogo y botánico italiano. Esta importante obra de taxonomía de hongos (escrita entre 1882 y 1890) es una lista con todos los nombres científicos utilizados y una breve descripción de los hongos. Estas descripciones siguen siendo referencias para los taxónomos actuales. Esta importante colección se encuentra depositada en el Instituto Spegazzini gracias a la generosa donación que hiciera el principal discípulo de Saccardo, el Dr. Carlos Spegazzini, y constituye la única colección de su tipo disponible en América del Sur.Material digitalizado en SEDICI gracias a la colaboración del Instituto de Botánica "Dr. Carlos Spegazzini" (Facultad de Ciencias Naturales y Museo, UNLP).Instituto de Botánica "Dr. Carlos Spegazzini

Hardware implementation of a broad-band vector spectrum analyzer based on randomized sampling

A hardware prototype of vector spectrum analyzer, which is based on a randomized sampling strategy and associated alias-free digital signal processing (DSP) algorithms, has been fully designed and implemented. The instrument exploits a couple of identical independently programmable digital data acquisition channels, whose synchronization allows to sample the input signal at instants that can be very close along the time axis (tens of picoseconds), against a maximum single-channel average throughput rate of 250 ksamples per second (kSa/s). This architecture has shown to be suitable for the accurate implementation of the randomized periodic sampling with uniform jitter on which the instrument is based. In addition, the design solutions adopted for the sampling command generators, which exploit the interaction between a digital gate signal and a phase-controlled sinusoidal wave, together with the particular analytical definition proposed for the spectral estimators, have allowed to make practically negligible the quantum time according to which the sampling instants are generated. Experimental results are provided, which validate both the alias-free spectrum analysis technique and the capability of the architecture proposed of reliably implementing the analytical benefits deriving from the randomized sampling strategy adopted

Accurate pHEMT nonlinear modeling in the presence of low-frequency dispersive effects

Low-frequency (LF) dispersive phenomena due to device self-heating and/or the presence of "traps" (i.e., surface state densities and bulk spurious energy levels) must be taken into account in the large-signal dynamic modeling of III-V field-effect transistors when accurate performance predictions are pursued, since these effects cause important deviations between direct current (dc) and dynamic drain current characteristics. In this paper, a new model for the accurate characterization of these phenomena above their cutoff frequencies is presented, which is able to fully exploit, in the identification phase, large-signal current-voltage (I-V) measurements carried out under quasi-sinusoidal regime using a recently proposed setup. Detailed experimental results for model validation under LF small- and large-signal operating conditions are provided. Furthermore, the I-V model proposed has been embedded into a microwave large-signal pseudomorphic high electron-mobility transistor (pHEMT) model in order to point out the strong influence of LF modeling on the degree of accuracy achievable under millimeter-wave nonlinear operation. Large-signal experimental validation at microwave frequencies is provided for the model proposed, by showing the excellent intermodulation distortion (IMD) predictions obtained with different loads despite the very low power level of IMD products involved. Details on the millimeter-wave IMD measurement setup are also provided. Finally, IMD measurements and simulations on a Ka-band highly linear power amplifier, designed by Ericsson using the Triquint GaAs 0.25-/spl mu/m pHEMT process, are shown for further model validation

Linearity improvement of VCSELs based radio over fiber systems utilizing digital predistortion

The article proposes a Digital Predistortion (DPD) methodology that substantially meliorates the linearity of limited range Mobile Front Haul links for the extant Long-Term Evolution (LTE) and future (5G) networks. Specifically, the DPD is employed to Radio over Fiber links that contrive of Vertical Cavity Surface Emitting Lasers (VCSELs) working at 850 nm. Both, Memory and Generalized Memory Polynomial models are implied to Single Mode (SM) and Multi-Mode (MM) VCSELs respectively. The effectiveness of the proposed DPD methodology is analyzed in terms of Normalized Mean Square Error, Normalized Magnitude, Normalized phase and Adjacent Channel Power Ratio. The demonstration has been carried out with a complete (Long Term Evolution) LTE frame of 10 ms having 5 MHz bandwidth with 64-QAM modulation configuration. Additionally, the effectuality of the proposed DPD technique is evaluated for varying levels of input power and link lengths. The experimental outcomes signify the novel capability of the implied DPD methodology for different link lengths to achieve higher system linearization

Automatic Extraction of Measurement-Based Large-Signal FET Models by Nonlinear Function Sampling.

A new method is proposed for the accurate experimental characterization and fully automated extraction of compact nonlinear models for Field-Effect Transistors (FETs). The approach, which leads to a charge-conservative description, is based on a single large-signal measurement under a two-tone sinusoidal wave excitation. A suitable choice of tone frequencies, amplitudes, and bias allows to adequately characterize the transistor over the whole safe operating region. The voltage controlled nonlinear functions describing the two-port FET model can be computed over an arbitrarily dense voltage domain by solving an overdetermined system of linear equations. These equations are expressed in terms of a new Nonlinear Function Sampling operator based on a bi-periodic Fourier series description of the acquired frequency spectra. The experimental validation is carried out on a 0.25-μm Gallium Nitride (GaN) on Silicon Carbide (SiC) High-Electron Mobility Transistor (HEMT) under continuous-wave (CW) and two-tone excitation (intermodulation distortion test).This project was partially supported by the Spanish Ministerio de Ciencia, Innovación y Universidades in the frame of ‘Salvador de Madariaga’ Program PRX18/00108