Mikael Garcia

Extensions of the Chalmers nonlinear HEMT and MESFET model

The ability to simulate temperature, dispersion, and soft-breakdown effects as well as a new /spl alpha/ dependence was added to the Chalmers nonlinear model for high electron mobility transistor (HEMTs) and metal semiconductor field-effect transistor (MESFETs). DC, pulsed dc, low frequency (10 Hz-10 MHz), RF, and small signal S-parameter measurements (1-18 GHz) have been made on a large number of commercial HEMT and MESFET devices from different manufacturers in the temperature range 17-400 K in order to evaluate the validity of the model extensions.

Accurate small-signal modeling of HFET's for millimeter-wave applications

In this paper we discuss the small-signal modeling of HFETs at millimeter-wave frequencies. A new and iterative method is used to extract the parasitic components. This method allows calculation of a /spl pi/-network to model the heterojunction field-effect transistor (HFET) pads, thus extending the validity of the model to higher frequencies. Formulas are derived to translate this /spl pi/-network into a transmission line. A new and general cold field-effect transistor (FET) equivalent circuit, including a Schottky series resistance, is used to extract the parasitic resistances and inductances. Finally, a new and compact set of analytical equations for calculation of the intrinsic parameters is presented. The real part of Y/sub 12/ is accounted for in these equations and its modeling is discussed. The accounting of Re(Y/sub 12/) improves the S-parameter modeling. Model parameters are extracted for an InAlAs/InGaAs/InP HFET from measured S-parameters up to 50 GHz, and the validity of the model is evaluated by comparison with measured data at 75-110 GHz.

An empirical table-based FET model

A new large signal field effect transistor (FET) model combining empirical and table based models was developed and investigated experimentally. The Chalmers empirical model was used as a spline function for the table based model. Combining models improves accuracy and simplifies and speeds extraction. The procedure can be applied for other types of devices.

An empirical-table based FET model

A new large signal field effect transistor (FET) model combining empirical and table based models was developed and investigated experimentally. The Chalmers empirical model was used as a spline function for the table based model. Combining models improves accuracy and simplifies and speeds extraction. The procedure can be applied for other types of devices.

A symmetrical nonlinear HFET/MESFET model suitable for intermodulation analysis of amplifiers and resistive mixers

We propose a new symmetrical heterojunction FET (HFET)/MESFET model to predict intermodulation distortion in amplifiers and resistive mixers. The model is symmetric. That is, drain and source of the intrinsic FET are interchangeable. This reflects the characteristics of most microwave FETs. The model has few fitting parameters and they are simple and straightforward to extract. The model was installed into Hewlett-Packards harmonic-balance program microwave design system and verified by measurements. The verification shows excellent results for an MESFET and an HFET in both amplifier and resistive mixer configurations.

Analog MMICs for millimeter-wave applications based on a commercial 0.14-/spl mu/m pHEMT technology

This paper describes recent results obtained from the monolithic-microwave integrated-circuit design activity at Chalmers University, Goteborg, Sweden. The goal is to design all circuits needed for the front end of a 60-GHz wireless local area network and to build various system demonstrators. Some recent experimental results from this activity like different 60-GHz amplifiers, a general-purpose IF amplifier, a 60-GHz resistive mixer, and frequency multipliers are reported in this paper. Parameters such as the gain, conversion loss, noise figure, dc-power dissipation, as well as the model used in the simulations are reported and discussed.

A new extraction method for the two-parameter FET temperature noise model

This paper presents a direct extraction method for the associated noise temperatures T/sub d/ and T/sub g/ in the field-effect transistor (FET) temperature noise model. The method is related to nodal analysis of circuits. T/sub d/ and T/sub g/ are extracted from the small-signal model parameters and the noise parameters of the device. It is also theoretically shown that there exist source admittances that cancel the thermal noise contribution at the output from either T/sub d/ or T/sub g/ in the model. Finally, a commercially available GaAs pseudomorphic high electron-mobility transistor (pHEMT) is measured and modeled for a wide range of bias points. Comparisons between measured and modeled noise parameters are presented in the 2-26 GHz frequency range.

A general parameter-extraction method for transistor noise models

A new general direct extraction procedure for transistor noise models including two correlated noise sources is developed. The extraction procedure is demonstrated for a Silicon Carbide (SiC) Metal Semiconductor Field Effect Transistor (MESFET). The extracted model shows good agreement to measured noise parameters.

On the performance of different HEMT cryogenic mixers

Performance of different HEMT mixers -i.e. gate, drain and resistive (microstrip and waveguide) has been studied experimentally at room and cryogenic temperatures. Conversion gain (loss for the resistive mixers) at cryogenic temperatures improves approximately 1/spl divide/1.5 dB. The noise figure improves too - all the mixers show 2-3 dB improvement in the noise figure performance.

A new millimeter-wave MMIC mixer for sensor applications

A new configuration of a MMIC gate mixer associated with a dual-polarized patch antenna was experimentally investigated at 94 GHz for the first time. A 7 dB reduction in the LO power requirement was experimentally observed when compared to a previously used resistive mixer. The new configuration with its low pumping power can significantly simplify the design of the LO sensor chain compared to the ordinary mixer configuration which consumes 3-10 dBm per device to attain a sufficiently low conversion loss for a typical radar application.