Search results for "Y-factor"
showing 10 items of 18 documents
Full characterization of low-noise HEMTs using only noise figure measurements
1993
A method for the complete characterization of microwave transistors in terms of noise, gain and scattering parameters using a computer-controlled noise figure measuring set-up only is presented. Selection of the optimum measuring conditions, all the steps of the experimental procedure, the data collecting and processing to derive all the parameters, are fully driven by an original (unpublished) software, even without the presence of an (unskilled) operator. Results are presented about the complete characterization of a series of ten pseudomorphicHEMTs in the 8-16 GHz range. The S-parameters are also compared with those measured by an ANA.
Langevin Approach to Understand the Noise of Microwave Transistors
2004
A Langevin approach to understand the noise of microwave devices is presented. The device is represented by its equivalent circuit with the internal noise sources included as stochastic processes. From the circuit network analysis, a stochastic integral equation for the output voltage is derived and from its power spectrum the noise figure as a function of the operating frequency is obtained. The theoretical results have been compared with experimental data obtained by the characterization of an HEMT transistor series (NE20283A, by NEC) from 6 to 18 GHz at a low noise bias point. The reported procedure exhibits good accuracy, within the typical uncertainty range of any experimental determin…
Advanced PSA Bipolar Transistors for Wireless Applications: Measurements of Scattering Parameters and Noise Figure
1994
A complete investigation on the performance of a series of double polysilicon self-aligned (PSA) bipolar transistors in terms of scattering parameters and noise figure is here reported. The devices have been characterized over the 1-4 GHz frequency range in several bias conditions to the aim of assessing the optimum bias values for the best trade-off between noise and gain performance. This is the first part of an extensive investigation currently performed on 5 families of PSA devices having different emitter configuration and size which have been manufactured by SGS-Thomson to undergo a comparative analysis on the global transistor performance.
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…
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.