IEEE MTT-S 2008 International Microwave Symposium Technical Program

Session: THP1F	Interactive Forum:
Chair:	Daniela Staiculescu, Georgia Institute of Technology
Co-Chair:	Ronglin Li, Georgia Institute of Technology

THP1F-01	A Scalable High Power Nonlinear HBT Model for a 28V HVHBT
1176	X. Zhang¹, F. Chau¹, B. Lin¹, X. Sun¹, W. Ma¹, P. Hu¹, J. Yao¹, C. Lee², ¹WJ Communications, San Jose, United States, ²National Chiao Tung University, Hsinchu, Taiwan
	A scalable nonlinear HBT model for a Building Block (1BB) of 28V InGaP/GaAs HBT is presented. It is based on the AgilentHBT (AHBT) model. The building block consists of 32 finger HBTs, an input pre-matching circuit and a transistor used as an emitter follower in the related bias circuit. The P1dB of 1BB is 32.5dBm. The model can account not only for DC, thermal, junction capacitances, S-parameters but also RF power, gain, IM3, operation current and collector efficiency. A good match between simulation and measurement has been achieved. By using a multiplicity parameter the model can accurately predict the DC and nonlinear RF performance of two Building Blocks (64 fingers, P1dB of 35.7dBm) and four Building Blocks (128 fingers, P1dB of 38.2dBm).

THP1F-02	RF Large-Signal Model for SiO2/AlGaN/GaN MOSHFETs
1180	J. Deng¹, W. Wang¹, S. Halder¹, W. R. Curtice¹, J. C. Hwang¹, V. Adivarahan², A. Khan², ¹Lehigh University, Bethlehem, United States, ²University of South Carolina, Columbia, United States
	For the first time, an RF large-signal model for GaN-based metal-oxide-semiconductor heterojunction field-effect transistors is extracted and validated. The model is based on the commercially available EEHEMT model that was originally developed for GaAs MODFETs. The model parameters were extracted from current-voltage characteristics and S parameters measured under both CW and pulsed conditions. The terminal impedances were extracted through global fitting over a wide frequency range, while the gate leakage across the oxide was modeled by a Schottky contact with a large ideality factor. Although the model simulates the Class-A power-amplifier performance of the unit transistor rather well, the EEHEMT model was found lacking in modeling gate capacitance nonlinearity and self heating and unsuitable for large transistors in reduced-angle power amplifiers.

THP1F-03	A New Empirical Model for the Characterization of Low-Frequency Dispersive Effects in FET Electron Devices Accounting for Thermal Influence on the Trapping State
1500	A. Raffo¹, V. Vadalà¹, G. Vannini¹, A. Santarelli², ¹University of Ferrara, Ferrara, Italy, ²University of Bologna, Bologna, Italy
	It is well known that low-frequency dispersive effects cause important deviations between static (dc) and dynamic electron device current\voltage (I\V) characteristics, which must be accurately accounted for in nonlinear device models for microwave circuit design. As a matter of fact, a very high level of accuracy has been obtained by exploiting modeling approaches based on bias-dependent model parameters. However, their practical use can be limited in the circuit design phase due to simulation time and memory occupation problems. On the other hand, too much simple models do not satisfy the accuracy requirements usually needed for first-run-success MMIC design. In this paper, a new analytical model for the characterization of low-frequency dispersive effects is presented, whose aim is essentially related to the request of very accurate prediction capabilities yet preserving the numerical efficiency.

THP1F-04	Harmonic balance simulation of a new physics based model of the AlGaN/GaN HFET
1527	H. Yin, D. Hou, G. L. Bilbro, R. J. Trew, North Carolina State University, Raleigh, United States
	HFETs fabricated with nitride-based wide bandgap materials are capable of producing high RF output power and are promising for the next generation radar and wireless communication systems. To take full advantage of this new kind of device, large-signal models suitable for use in commercial microwave circuit simulators are desirable, but existing models can only interpolate or fit data that has been measured from previously fabricated devices. In this study, a new physics-based large-signal model for AlGaN/GaN HFETs is introduced that can predict the large-signal performance of an HFET from its design parameters. It couples a compact physics-based DC module with a harmonic balance RF module. This new model is shown to agree with both DC and RF experimental data without any adjustable fitting parameters for the device. The DC IV and transconductance curves predicted by this new model also agree with those generated by a commercial 2D simulator.

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