The high electron mobility transistor's (HEMT's) noise behavior is presented from theoretical and experimental points of view. The general method used in the high-frequency noise analysis is described and the different approximations commonly used in the derivation of the noise parameter expressions are discussed. A comparison between the noise performance of both MESFETs and HEMTs is carried out. The measurement techniques providing the noise figure and the other noise parameters are then described and compared. >

Noise modeling and measurement techniques (HEMTs)

Transmission of Information by Orthogonal Functions

This paper presents a new approach for the definition and identification of a transistor model suitable for low-noise amplifier (LNA) design. The resulting model is very robust to layout modifications (i.e., source degeneration) providing accurate predictions of device noise-performance and small-signal parameters. Moreover, the described procedure is very robust since it does not require any numerical optimization, with possibly related problems like local minima and unphysical model parameters. The adopted model topology is based on a lumped element parasitic network and a black-box intrinsic device, which are both identified on the basis of full-wave electromagnetic simulations, as well as noise and ${ S}$ -parameter measurements. The procedure has been applied to three GaN HEMTs having different peripheries and a Ku-band LNA has been designed, demonstrating a very good agreement between measurements and predicted results.

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GaN HEMT Noise Model Based on Electromagnetic Simulations

A method to determine noise parameters of microwave linear two-ports (transistors) is presented which is based on a two-channel noise temperature measuring system and an analycal data procesing procedure. As compared with the one-channel measurements and the graphical processing techniques, the method offers advantages from both accuracy and experiment viewpoints. Experimental verification related to noise parameters determination for a microwave transistor as function of frequency in S band are reported.

Determination of Microwave Two-Port Noise Parameters Through Computer-Aided Frequency-Conversion Techniques

Neural networks are proposed for efficient temperature-dependent modeling of small-signal and noise performances of low-noise microwave transistors over a wide temperature range. The proposed models can be based either on neural networks only or on a combination of neural networks and empirical transistor models. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005.

Temperature-dependent models of low-noise microwave transistors based on neural networks

A method for the complete characterization of GaAs FET's in terms of noise parameters (F/sub o/,Gamma/sub on/, R/sub n/), gain parameters (G/sub ao/, Gamma /sub og/, R/sub g/), and of those scattering parameters ( S/sub11/, S/sub22/|,S/sub12/| S/sub21|, /spl angle/S/sub 12/S/sub 21/ ) that are needed for low-noise microwave amplifier design is presented. The instrumentation employed, i.e., a noise-figure measuring system equipped with a vectorial reflectometer, as well as the time consumption, are the same required for the determination of noise parameters only through conventional methods. The measuring setup and the experimental procedure are described in detail. Considerations about the computer-aided data processing technique are also provided. As an experimental result, the characterization of a sample device versus frequency (4-12 GHz) and drain current is reported. A comparison between the scattering parameters provided by the method and those measured by means of a network analyzer is also included.

Characterization of GaAs FET's in Terms of Noise, Gain, and Scattering Parameters through a Noise Parameter Test Set

By means of an automatic measuring system which allows the rapid and accurate characterization of microwave transistors in terms of noise and scattering parameters simultaneously, 32 HEMTs of four manufacturers have been tested From the experimental data so obtained the equivalent circuit of the 'typical' device which represents each transistor set has been extracted using a decomposition technique This procedure allows the optimum fitting of the global performance by exploiting the correlation between the model elements and the measured parameters over the operating frequency range Since the method takes into account also the noise behavior of several devices of each series, a substantial improvement of the model performance for use in (M)MIC CAD of low-noise amplifiers is obtained >

HEMT for low noise microwaves: CAD oriented modeling

The performance of microwave noise parameters of HEMTs vs. temperature has been investigated by applying a new simplified measurement procedure, such method relies on the extraction of a noisy circuit model from measured scattering parameters together with one noise figure measurement in input matched conditions, (namely, F/sub 50/). Then the four noise parameters of the device under test are extracted using a suitable computer-aided model analysis. Further investigation have been carried out to verify the reliability of the prediction of F/sub 50/ values vs. temperature by means a simple noise temperature ratio.

Microwave noise parameters of HEMTs vs. temperature by a simplified measurement procedure

A simplified approach for the determination of the noise parameters of high electron-mobility transistors (HEMT's) at microwave frequencies has already been presented for devices tested at room temperature. Such method relies on the extraction of a noisy circuit model from measurements of the scattering parameters and the noise figure at the fixed source impedance of 50 /spl Omega/ (namely, F/sub 50/). The noise parameters of the device are then computed by model simulation. They exhibited a very good agreement with the noise parameters determined by the experimental procedure. In the present work, commercial pseudomorphic HEMT'S have been characterized at different temperatures in the 6 GHz to 18 GHz frequency range for validating the use of a further simplified procedure. We here show how to determine the complete noise performance of the devices from a very reduced set of measurements, i.e., the scattering parameters at each selected temperature and the F/sub 50/ noise figure at room temperature. The computed noise parameters are compared with those determined by application of the measurement procedure. The results show that the very simplified method can be employed with a good degree of accuracy whenever rapid noise testing of HEMT's versus temperature is needed.

Determination of HEMT's noise parameters versus temperature using two measurement methods

A method for the simultaneous determination of transistor noise and gain parameters through noise figure measurements has been presented recently. An improved version of the method is presented here which can also yield all the scattering parameters needed for designing amplifiers. By means of a proper (computer-aided) data-processing technique, s11, s22, |s12| , |S21|, and \s12s21 are determined. As experimental verifications, the characterization of a GaAs MESFET versus frequency (4-8 GHz) is reported.

M. Sannino

Papers

Characterization of GaAs FET's in Terms of Noise, Gain, and Scattering Parameters through a Noise Parameter Test Set

HEMT for low noise microwaves: CAD oriented modeling

Microwave noise parameters of HEMTs vs. temperature by a simplified measurement procedure

Determination of HEMT's noise parameters versus temperature using two measurement methods

Simultaneous Determination of Transistor Noise, Gain, and Scattering Parameters for Amplifier Design through Noise Figure Measurements Only