Search results for " Generator"

Comparison between two measuring methods for complete characterization of low-noise HEMTs at microwaves

1996

The good performances of a set-up for the complete characterization of HEMTs up to 40 Ghz in terms of noise and scattering parameters through noise figure measurements only are shown by many experimental results. Because of some inconveniences in practice the use of the method is suggested for research laboratories only. For industrial applications an alternative symplified method is proposed whose performances are shown to be in surprising agreement with the ones of the standard method.

ACCURATE MEASUREMENTS OF OPTIMUM NOISE PARAMETERS OF MICROWAVE TRANSISTORS

1986

A method for measuring losses of the tuner network used as noise source admittance transformer in transistor noise parameter test-set is presented. Since the method is based on noise figure measurements, tuner losses can be determined on-line while performing measurements for determining transistor noise parameters. As experimental verifications the optimum noise parameters of a GaAs FET in the 4 - 12 GHz frequency range, measured through a computer-assisted measuring system, are reported.

Noise parameters of HEMTs: analysis of their properties from a circuit model approach

1996

Noise parameters of high electron mobility transistors (HEMT) at microwave frequencies are a subject of active research since the knowledge of their performance is of key importance for the use of these devices for designing low‐noise amplifiers. Employs a simple noise model to derive the analytical expressions for the device noise parameters F0, Γ0 and N in terms of the electrical elements associated with the basic equivalent circuit of an HEMT. Analyses such expressions to establish some fundamental relationships, as well as the expected noise performance of the device when the parasitic elements representing package effects are included.

On the determination of device noise and gain parameters

1979

The least-squares fitting of measured noise figures and gains versus input termination admittance is an established procedure to determine linear two-port noise and gain parameters. Unfortunately, the method is liable to the serious inconvenience of yielding often erroneous results or even results without physical meaning. Some criteria are suggested which allow the carrying out of measurements in such a manner as to safely avoid the above drawbacks.

Influence of the temperature on the equivalent noise resistance of HEMTs at microwave frequencies

1998

Abstract This paper is focused on the performance of the noise resistance Rn of HEMTs at microwave frequencies as a function of temperature. A sensitivity analysis has been performed on several noisy circuit models of low-noise devices that we had previously characterized in terms of scattering and noise parameters. Such a study has been aimed at pointing out the role played by either the electrical elements and the noise temperatures of the resistors of the equivalent circuit on the typically observed U-shaped behavior of Rn.

Complete characterization of low-noise devices at microwave frequencies: two alternative procedures for HEMTs

1995

Signal to Noise Ratio of Silicon Photomultipliers measured in the Continuous Wave Regime

2014

We performed a Signal to Noise Ratio characterization, in the continuous wave regime, at different bias voltages, frequencies and temperatures, on a novel class of silicon photomultipliers fabricated in planar technology on silicon p-type substrate. Signal to Noise Ratio has been measured as the ratio of the photogenerated current, filtered and averaged by a lock-in amplifier, and the Root Mean Square deviation of the overall current flowing to the device. The measured noise takes into account the shot noise, resulting from the photocurrent and the dark current. We have also performed a comparison between our SiPMs and a photomultiplier tube in terms of Signal to Noise Ratio, as a function …

Preliminary Thermo-Mechanical Design of the Once Through Steam Generator and Molten Salt Intermediate Heat Exchanger for EU DEMO

2020

The European DEMOnstration power plant (DEMO) is considered to be the nearest-term fusion reactor capable of producing several hundred MWs of net electricity, operating with a closed tritium fuel-cycle (achieving the tritium self-sufficiency), and qualifing technological solutions for a fusion power plant with different breeding blanket (BB) concepts that are under investigation. The BB is a key component for the development of the DEMO plant design and, in particular, of those systems having the responsibility to remove the plasma-generated thermal power and its conversion in the electrical energy. This study deals with the preliminary thermo-mechanical design of the heat exchangers and st…

Sensitivity Analysis of the MASLWR Helical Coil Steam Generator Using TRACE

2011

Accurate simulation of transient system behavior of a nuclear power plant is the goal of systems code calculations, and the evaluation of a code's calculation accuracy is accomplished by assessment and validation against appropriate system data. These system data may be developed either from a running system prototype or from a scaled model test facility, and characterize the thermal hydraulic phenomena during both steady state and transient conditions. The identification and characterization of the relevant thermal hydraulic phenomena, and the assessment and validation of thermal hydraulic systems codes, has been the objective of multiple international research programs. The validation and…

Frequency-agile gyrotron for electron decoupling and pulsed dynamic nuclear polarization.

2017

We describe a frequency-agile gyrotron which can generate frequency-chirped microwave pulses. An arbitrary waveform generator (AWG) within the NMR spectrometer controls the microwave frequency, enabling synchronized pulsed control of both electron and nuclear spins. We demonstrate that the acceleration of emitted electrons, and thus the microwave frequency, can be quickly changed by varying the anode voltage. This strategy results in much faster frequency response than can be achieved by changing the potential of the electron emitter, and does not require a custom triode electron gun. The gyrotron frequency can be swept with a rate of 20 MHz/μs over a 670 MHz bandwidth in a static magnetic …