Search results for "Noise Figure"

A Method for Accurate Measurements of Optimum Noise Parameters of Microwave Transistors

1985

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.

Influence Of The Model Parameters On The Noise Performance Of Double-polysilicon BJTs For Microwave LNA's

1997

In the recent post we have measured the noise and the scattering parameters of several series of double polysilicon BJT's over the 2-6 GHz frequency range at different collector current values, according to their emitter finger number. From the experimental data, a noisy circuit model has been extracted based on a T-equivalent network. By means of the correlation matrix techniques, novel analytical expressions of the noise parameters have been derived. As a second step, a sensitivity analysis has been performed for evaluating the influence of each model element on the noise performance. The results show how to improve the characteristics of such devices for a better performance when employe…

Three Different Methods for Determining the Microwave Noise Parameters of HEMT's at Decreasing Temperatures

1998

The noise characteristics of any transistor are usually represented by means of four parameters which are frequency-, bias- and temperature-dependent, similarly to the scattering parameters. The noise parameters are determined by a standard indirect procedure based on multiple noise figure measurements and appropriate data processing techniques requiring a complex instrumentation set-up and skilled operators. As an alterative way, we have shown that the noise parameters of packaged HEAMT's can be computed with very good accuracy from the analysis of a noisy circuit model derived from the scattering parameters plus a single noise figure measurement. A third way exists for the determination o…

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.

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 …

Temperature Dependence of pHEMT-Based LNA Performance for VSAT Applications

1994

From a complete characterization in terms of noise and scattering parameters carried out at room temperature in the 8-16 GHz frequency range, the noisy small-signal model of a pseudomorphic HEMT series has been extracted. The transistor scattering parameters have been subsequently measured at lower temperatures (down to -50 °C) by placing the device text fixture in a thermo-controlled chamber. An accurate noisy model has then been extracted by determining the circuit element values at the different temperatures. The trade-off performance of a pHemt-based LNA for VSAT receiver system applications has been investigated vs. frequency and temperature.

Typical Aspects of the Microwave Noise Performance of HEMTs at Decreasing Temperatures

1996

In analog signal processing at microwave frequencies the noise performance of active devices is of fundamental importance for the accurate design of low-noise amplifiers. To this aim, the determination of the four noise parameters F O , Γ O (complex variable) and Rn has to be accomplished together with the usual scattering parameter measurements vs. frequency. In addition, the dependence of the device performance vs. temperature is of interest for circuit applications characterized by harsh environmental conditions. In this work the noise behavior of high electron mobility transistors has been investigated by means of measurements and modeling in the 2-18 GHz frequency range and as a functi…