0000000001150954
AUTHOR
A. Caddemi
Influence Of The Model Parameters On The Noise Performance Of Double-polysilicon BJTs For Microwave LNA's
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…
Typical Aspects of the Microwave Noise Performance of HEMTs at Decreasing Temperatures
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…
Noise parameters of HEMTs: analysis of their properties from a circuit model approach
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.
Comparison between complete and simplified methods for determining the microwave noise parameters of HEMTs
Modem automatic noise parameter measuring systems are based on measurements of some values of F(rs ) for different values of IГs (more than four, for redundancy) realized by adjusting an admittance transformer (tuner) inserted between the noise source and the TUT mput . Such values are then manipulated by means of proper data processing techniques using eqn.( 1) [ 11. This measuring procedure is hereafter referred to as standard to point out that the old `Standards on methods of measuring noise in linear twoports´ published by the IRE Subcommittee on noise in 1960 is considered obsolete by all the experimenters.
Influence of the temperature on the equivalent noise resistance of HEMTs at microwave frequencies
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
Fast and efficient procedures for determining the microwave noise parameters of HEMT's at decreasing temperatures
Noise parameters are an electrical representation of the noise performance of transistors which is widely used in reliability studies as well as in the design of low-noise microwave amplifiers. Such parameters are usually determined by employing a complex indirect (standard) procedure based on multiple noise figure measurements and appropriate data processing techniques. We report here two altemative and rapid methods used to perform the complete noise characterization of HEMT's at decreasing temperatures over the 6 to 18 GHz frequency range. The results show a very satisfactory agreement.among the different procedures thus assessing the inherent consistency of the global approach to the pr…
TEMPERATURE DEPENDENT NOISY MODELS OF PSEUDOMORPHIC HEMTs
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 pseudomotphic 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. The model effectiveness has then been tested by determining the circuit element values at the different temperatures and by observing the model noise performance.
Three Different Methods for Determining the Microwave Noise Parameters of HEMT's at Decreasing Temperatures
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…
Advanced PSA Bipolar Transistors for Wireless Applications: Measurements of Scattering Parameters and Noise Figure
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.
Full characterization of low-noise HEMTs using only noise figure measurements
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.
Microwave effects on isolated chick embryo hearts.
This study was designed to examine the effects of microwaves on the electric activity of hearts as a means of elucidating interactive mechanisms of nonionizing radiation with cardiac tissue. Experiments were performed on isolated hearts of 9-12-day-old chick embryos placed in small petri dishes. Oxygenated isotonic Ringer's solution at 37 degrees C permitted heart survival. Samples were irradiated at 2.45 GHz with a power density of 3 mW/cm2. The heart signal was detected with a glass micropipet inserted into the sinoatrial node and examined by means of a Berg-Fourier analyzer. Pulsed microwaves caused the locking of the heartbeat to the modulation frequency, whereas continuous wave irradia…
Langevin Approach to understand the Noise in Microwave Transistors
A noise analysis procedure for microwave devices based on Langevin approach is presented. The device is represented by its equivalent circuit with the internal noise sources included as stochastic processes. Fromthe circuit network analysis a stochastic integral equation for the output voltage is derived and fromits power spectrumthe 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) from6 to 18 GHz at a low noise bias point. The reported procedure exhibits good accuracy, within the typical uncertainty range of any experimental de…
Comparison between two measuring methods for complete characterization of low-noise HEMTs at microwaves
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.
microwave effects on isolated chick embrio heart
This study was designed to examine the effects of microwaves on the electric activity of hearts as a means of elucidating interactive mechanisms of nonionizing radiation with cardiac tissue. Experiments were performed on isolated hearts of 9-12-day-old chick embryos placed in small petri dishes. Oxygenated isotonic Ringer's solution at 37 degrees C permitted heart survival. Samples were irradiated at 2.45 GHz with a power density of 3 mW/cm2. The heart signal was detected with a glass micropipet inserted into the sinoatrial node and examined by means of a Berg-Fourier analyzer. Pulsed microwaves caused the locking of the heartbeat to the modulation frequency, whereas continuous wave irradia…
Temperature Dependence of pHEMT-Based LNA Performance for VSAT Applications
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.