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ABSTRACT: In this paper Low Frequency (LF) parasitic effects are assessed through three kinds of measurements. It is shown that LF S-parameters measurements allow to extract the thermal impedance of Heterojunction Bipolar Transistors (HBTs) and to put dispersive effects of AlGaN/GaN High Electron Mobility Transistors (HEMTs) into evidence. Large signal (RF pulsed and two tone intermodulation) confirm the impact of those parasitic effects on performances of Power Amplifiers.
Wireless and Microwave Technology Conference (WAMICON); 01/2012
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ABSTRACT: In this paper a systematic analysis of thermal and trapping behaviour of microwave power AlGaN/GaN HEMTs has been carried out through pulsed current-voltage (PIV) measurements and S parameters. It is shown that the thermal resistance of the device can be accurately determined provided that some assumptions on the trapping behaviour of the device are verified. The values obtained have been checked by three dimensional finite element (3D-FE) simulations with reasonable accuracy. Kink effects in the output characteristics have been analysed at different temperatures and it has been shown that they are more pronounced at ambient temperature. Finally the microwave behaviour of the device versus temperature has been assessed.
Microwave Integrated Circuits Conference (EuMIC), 2010 European; 10/2010
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ABSTRACT: In this letter, we present a characterization method for the determination of the thermal impedance of heterostructure bipolar transistors. The thermal impedance was characterized using low-frequency S -parameter measurements. We will show that our method can be used to characterize the thermal impedance independent of the transistor size.
IEEE Electron Device Letters 10/2010; · 2.85 Impact Factor
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ABSTRACT: This paper has two main axis: firstly, we address the experimental characterization of the frequency-dependent thermal impedance of microwave bipolar transistors from continuous wave (CW)-only measurements (both DC and AC). From the experimental perspective, we will review some of the already available methods and propose a new method based on a recent observation. It will be shown that under proper measurement control, a reasonable precision of the computed value can be achieved. The method is applied to characterize the global (external) behavior of a multi-finger Heterojunction Bipolar Transistor (HBT), whose physical structure is known. A distributed thermal circuit, entirely derived from 3D thermal simulations, is incorporated into a complete distributed electrothermal model of the device, whose global behavior is validated by measurements. Then from a distributed electrothermal simulation perspective, we will address the power and temperature distribution between fingers as a function of the power dissipated by the device, and will show that the global behavior in measurements is close to the worst case in terms of highest temperature among individual fingers.
Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm), 2010 12th IEEE Intersociety Conference on; 07/2010
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Microelectronics Journal. 01/2010; 41:554-559.
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IEEE MTT-S International Microwave Symposium Digest; 01/2009
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ABSTRACT: This paper presents an analysis of the impact ionization phenomenon encountered in AlGaAs/GaInAs/GaAs PHEMTs. Two characterizations techniques have been used. At first, pulsed S-parameter measurements in the Impact Ionization (II) region have been required to identify the cut-off frequency of the phenomenon. Then, using these measurements, we propose a new small-signal model taking into account the frequency transition between quasi-static characteristics measured in pulsed conditions and microwave characteristics. Finally, this model has been tested in large signal conditions and the simulation results were checked through Load Pull Time domain Measurements (LPTM) to assert the validity of the model.
Microwave Integrated Circuit Conference, 2008. EuMIC 2008. European; 11/2008
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ABSTRACT: This paper deals with an electrothermal model of high power heterojunction bipolar transistor (HBT) intended for CAD. The first section describes the model topology and sets the implemented equations that allow to take into account of the physical phenomena. The model also integrates scaling rules function of emitter length (W) and number of fingers (N). For the thermal aspect, low frequency impedance measurement approach has been led. Model simulations have been compared to quasi-isothermal I-V measurements, pulsed S parameters measurements, and load-pull multi-harmonics measurements.
Microwave Integrated Circuit Conference, 2008. EuMIC 2008. European; 11/2008
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ABSTRACT: This paper presents a dual approach for a coherent determination and validation of HBT thermal impedance. This study relies both on an experimental characterization method and a 3D finite element simulation approach. The first section reminds briefly the experimental approach. The second section describes the 3D device modeling used for the physic-based thermal simulations. Thereafter, details on the reduction method used for the numerical computation of the thermal impedance are explained. The last section compares the final results and validates this dual approach for power HBTs.
Thermal Inveatigation of ICs and Systems, 2008. THERMINIC 2008. 14th International Workshop on; 10/2008
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ABSTRACT: System-level models simplify the analysis of complex RF systems, such as transmission-reception modules, by expressing global input-output relationships. However, the development of high RF power models for nonlinear subsystems requires the prediction of the distortion induced by low-frequency memory effects such as self-heating effects. In this framework, we present a new electrothermal behavioral model for power amplifiers. This global model is based on the coupling between a behavioral electrical model derived from the transistor-level description of the amplifier and a thermal reduced model. This model, implemented into a circuit simulator, allows to predict the impact of the thermal effects in pulsed RF mode thanks to an envelope transient analysis. This approach has also been validated by measurements.
IEEE Transactions on Microwave Theory and Techniques 12/2007; · 1.85 Impact Factor
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ABSTRACT: This paper deals with the simulation and the design of an active dual stage high power S band limiter. The contribution of this work relies on an accurate nonlinear PIN diode model that has been used to predict the limiter performances. This model takes into account recombination phenomenon in the heavily doped region and include junctions effects. In the first section, the model is presented and validated by measurement results on two thin diodes. In the second section, the limiter output power and isolation characteristics are validated by power measurements up to +55 dBm and by spectrum measurements.
Microwave Integrated Circuit Conference, 2007. EuMIC 2007. European; 11/2007
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ABSTRACT: This paper considers a new approach for nonlinear system level models dedicated to high RF power amplifiers. The constant increase of power density imposes to take into account of thermal effects. In this framework, a new electro-thermal behavioral model based on the coupling between a behavioral electrical model and a thermal reduced model predicting the operating temperature of the amplifier is expressed for radar application. This model has been successfully implemented into the Agilent Advanced Design System (ADS) circuit simulator. The transient thermal effects have been simulated thanks to an envelope transient analysis.
Microwave Integrated Circuit Conference, 2007. EuMIC 2007. European; 11/2007
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ABSTRACT: The optimization of the small and large signal performances of a radio frequency (RF)-LDMOS is presented via the achievement of a novel LDMOS architecture. Specific process steps are introduced into a 0.25-mum BiCMOS technology and precisely described to realize a fully salicided gate RF-LDMOS architecture. Significant improvement is obtained on the small-signal - f<sub>T</sub> and F<sub>max</sub> - and power performances while maintaining good dc characteristics
IEEE Transactions on Electron Devices 05/2007; · 2.32 Impact Factor
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ABSTRACT: An improved formulation of the frequency-dependent impedance for p-i-n diodes from physical and geometrical parameters is presented. This work is addressed to diode designers and allows them to evaluate quickly and accurately the diode impedance. It comes in parallel with existing SPICE p-i-n diode model used in CAD software. Under forward bias conditions, important recombinations occur in the heavily doped end regions of thin p-i-n diodes that seriously affects the diode impedance. This effect is taken into account to increase the accuracy of existing numerical models and to extend their validity domain to any I-region thicknesses. This improvement has been validated by measurement results on a 5-mum I-region width silicon p-i-n diode
IEEE Microwave and Wireless Components Letters 04/2007; · 1.72 Impact Factor
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ABSTRACT: A p-i-n diode model for switching and limiting applications is presented. The model allows to simulate the I-region store charge effect that governs the impedance-frequency characteristic of the diode. The model also includes recombination phenomenon in the heavily doped region and junctions effects. The diode model has been implemented in a commercial circuit simulator and validated with a good agreement by measurement results
European Microwave Integrated Circuits Conference, 2006. The 1st; 10/2006
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Microwave Conference, 2004. 34th European; 11/2004
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ABSTRACT: An optimized LDMOSFET and a SiGe:C HBT for PA design, integrated in a BiCMOS technology, are described in this article. Each device of interest, for PA applications, is highlighted via its electrical performance - static, small and large signal.
Bipolar/BiCMOS Circuits and Technology, 2004. Proceedings of the 2004 Meeting; 10/2004
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ABSTRACT: It is usual to say that power GaInP/GaAs heterojunction bipolar transistors (HBTs) have many advantages for power amplification at microwave frequencies, because of their high gain and high power density. Furthermore, the possibility of controling the base biasing conditions (voltage, current, self-bias control) compared to a field-effect transistor offers additive degrees of freedom to make a tradeoff between linearity and power-added efficiency. Nevertheless existing devices are limited because of the relatively low breakdown voltage whereas high collector voltage swings are required to achieve high power. This drawback makes them not appropriate for use in the next generation of mobile communication base station or radar systems. Silicon technologies such as LDMOS and III-V devices (MESFET and HFET) present competitive performances in term of high power level but for medium power added efficiency. Important improvements have been made in recent years which make possible large breakdown voltages for GaInP/GaAs HBTs. Breakdown value close to 67 V has been achieved. The aim of this work is to significantly improve the modeling of the breakdown voltage on this type of transistor. Furthermore, the in depth characterization and modeling of self-heating effects have been greatly improved in order to improve thermal management solutions which enable us to enhanced design solutions of HBT high power amplifiers.
IEEE Transactions on Microwave Theory and Techniques 01/2003; · 1.85 Impact Factor
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ABSTRACT: As the size of the semiconductor devices is getting smaller and as the power density is getting higher with advanced technology, self-heating effects in power devices are becoming important. Electrothermal models of whole power devices are necessary for an accurate analysis of their performances. This paper deals with the integration of a reduced thermal model based on a three-dimensional finite element (FE) thermal simulation into circuit simulator for an accurate prediction of the electrothermal behavior of power devices. The reduced thermal model based on the Ritz vectors approach can be easily implemented in any kind of circuit simulator because it is described by a SPICE format subcircuit. The model has been successfully experimented with the Advanced Design Simulator (ADS). Electrical based thermal measurements of transient temperature response have successfully validated the approach. Coupled to a distributed electrical model, this electrothermal model has been used in order to simulate the instability phenomenon known as "the current collapse phenomenon" which can occur in multi-finger heterojunction bipolar transistors (HBTs).
Thermal and Thermomechanical Phenomena in Electronic Systems, 2002. ITHERM 2002. The Eighth Intersociety Conference on; 02/2002
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ABSTRACT: In this paper, a global method is proposed to characterize the
electrothermal behavior of multi-fingered Pseudomorphic High
Electron-Mobility Transistors (PHEMTs). The method is based on the
coupling of circuit, electromagnetic and thermal softwares. It is shown
that scaling rules have just to be applied for intrinsic performances of
a transistor when extrinsic elements and thermal effects are rigorously
taken into account
Microwave Symposium Digest, 2002 IEEE MTT-S International; 02/2002
