The Mediterranean Forecasting System - Part 1: Evolution and performance

The Mediterranean Forecasting System produces operational analyses and reanalyses and 10 d forecasts for many essential ocean variables (EOVs), from currents, temperature, salinity, and sea level to wind waves and pelagic biogeochemistry. The products are available at a horizontal resolution of 1/24 (approximately 4 km) and with 141 unevenly spaced vertical levels. The core of the Mediterranean Forecasting System is constituted by the physical (PHY), the biogeochemical (BIO), and the wave (WAV) components, consisting of both numerical models and data assimilation modules. The three components together constitute the so-called Mediterranean Monitoring and Forecasting Center (Med-MFC) of the Copernicus Marine Service. Daily 10 d forecasts and analyses are produced by the PHY, BIO, and WAV operational systems, while reanalyses are produced every ∼ 3 years for the past 30 years and are extended (yearly). The modelling systems, their coupling strategy, and their evolutions are illustrated in detail. For the first time, the quality of the products is documented in terms of skill metrics evaluated over a common 3-year period (2018-2020), giving the first complete assessment of uncertainties for all the Mediterranean environmental variable analyses. © 2023 Giovanni Coppini et al

Recognizing vertebral artery dissection in children: a case report.

Vertebral artery dissection is an unusual cause of stroke especially in children. The majority of dissections are thought to be caused by trauma although in many cases the trauma may be trivial. In other cases, certain underlying pathological processes are thought to be risk factors. We report a case of vertebral artery dissection in a 9-year-old child who presented with neurologic deficits suggestive of a posterior circulation stroke. The signs and symptoms of this unusual entity can be subtle and intermittent over a period of days to weeks; thus, making it very difficult to recognize. Therefore, it is important to consider the possibility of vertebral artery dissection in the differential diagnosis of neurologic deficits in children

A C-band GaAs-pHEMT MMIC low phase noise VCO for space applications using a new cyclostationary nonlinear noise model

This paper describes the design and implementation of a C-band MMIC VCO developed in the framework of activities oriented to the improvement of products for space applications. The circuit exploits a single device with a microstrip integrated resonator coupled with varactors. The exploited technology is a space-qualified GaAs 0.25-um pHEMT process. The MMIC exhibits 350-MHz bandwidth at 7.3 GHz, with 14 dBm output power and -86 dBc/Hz single side-band phase noise at 100 kHz from the carrier. Measured performances are in good agreement with simulations. The active device adopted for the design was characterized in terms of both low-frequency noise in quiescent bias-dependent operation and its up-conversion into phase noise under large-signal RF oscillating conditions, using in-house developed measurement setups. A new compact nonlinear noise model was identified, implemented and exploited for phase noise simulations. The model features cyclostationary equivalent noise generators. Comparisons between measurements and simulations show that the nonlinear cyclostationary modeling approach is more accurate than conventional noise models in oscillator phase noise analyses of pHEMT based circuits

A V band singly balanced diode mixer for space application

The paper describes the design of a V band single balanced mixer to be employed in the front end of an on-board receiver for space applications. The V band receiver is a demonstrator for the use of different monolithic processes and interconnection/assembly technologies in space applications at such high frequencies. The receiver front-end consists of a multi-stage LNA amplification followed by an image reject filter, the mixer and a frequency doubler for the local oscillator. All the chips are mounted over an LTTC substrate using bumps/hot vias technology. Chip to chip interconnection is provided by coplanar wave guide on LTTC. The mixer employs a rat race 180\ub0 hybrid to balance the local oscillator and a couple of Schottky diodes as mixing elements. The technology employed is a 0.15μm pHMET process that offers diodes with a cut off frequency higher that 300GHz. The choices made for the mixer type and topology starting from the system specifications are covered in the paper along with the actual description of the circuit design

A V band singly balanced diode mixer for space application

The paper describes the design of a V band single balanced mixer to be employed in the front end of an on-board receiver for space applications. The V band receiver is a demonstrator for the use of different monolithic processes and interconnection/assembly technologies in space applications at such high frequencies. The receiver front-end consists of a multi-stage LNA amplification followed by an image reject filter, the mixer and a frequency doubler for the local oscillator. All the chips are mounted over an LTTC substrate using bumps/hot vias technology. Chip to chip interconnection is provided by coplanar wave guide on LTTC. The mixer employs a rat race 180° hybrid to balance the local oscillator and a couple of Schottky diodes as mixing elements. The technology employed is a 0.15μm pHMET process that offers diodes with a cut off frequency higher that 300GHz. The choices made for the mixer type and topology starting from the system specifications are covered in the paper along with the actual description of the circuit design

10 Watt High Efficiency GaAs MMIC Power Amplifier for Space Applications

This paper describes the design of a GaAs monolithic high power amplifier at Ku band. The chip delivers about 40 dBm of saturated output power, in CW operating conditions, at 11.7 GHz central frequency, with 17% of bandwidth. The saturated power gain is 12.4 dB with 2 dB gain flatness across the application bandwidth while the chip power added efficiency is estimated between 33% to 47%. The amplifier is designed to be used as final stage of a downlink satellite transmitter for Tracking Telemetry & Command system. A commercial power p-HEMT process capable of handling a power density higher than 1 W/mm has been selected for the MMIC design. Due to the space application, special attention must be put on the process and MMIC reliability: to this aim performances must be guaranteed in de-rated conditions respect to the process maximum ratings and, in addition, the channel temperature of the active devices must be kept within the value established by Space Requirements and carefully controlled. This makes the design objective very tight. The MMIC power amplifier design and some measurement results are presented in the paper

Design of L and X band class E power amplifiers with GaAs pHEMT technology for space SAR

The paper describes the design of class E power amplifiers for SAR space applications, exploiting a 0.35-um pHEMT GaAs process. An L-band 10-Watt push-pull hybrid amplifier has been designed and implemented. The HPA features 73% PAE and 81% drain efficiency at 1.275 GHz. The performances of the class E HPA are also compared with a class AB HPA, exploiting the same technology. Class E design was also evaluated at X band, which for this technology is beyond the limit for the devices' class E operation capability. Two different prototype amplifiers were designed exploiting different device periphery. The single-cell amplifier delivers about 31 dBm output power with 64% peak PAE, whereas the double-cell circuit features 27 dBm output power with 70% peak PAE. These prototype amplifiers prove the possibility to use this process for the design of X band MMIC HPA for SAR space applications operating with high efficiency