RT Dissertation/Thesis
T1 HBT and Schottky diode table-based nonlinear models for microwave integrated circuits design
A1 Rodriguez Testera, Alejandro
K1 3307.08 Dispositivos de Microondas
K1 3307.19 Transistores
K1 3307.03 Diseño de Circuitos
AB Accurate active device nonlinear models are key elements in the design of Microwave Integrated Circuits (MICs) with Circuit Aided Design (CAD) tools. There is a large diversity of nonlinear models proposals, each one with their own formulation and characteristics. The most popular ones are empirical, in the sense that model parameters are extracted from electrical measurements, and they could be classified in analytical/compact and black-box (both, table-based and behavioral). Analytical models are usually time domain approaches based on nonlinear analytical expressions, which try to reproduce the instantaneous device nonlinear behavior. In the case of HBT (Heterojunction Bipolar Transistor) transistors, the poor thermal conductivity of III-V materials combined with the high power densities of the HBT operation makes thermal modeling compulsory for these devices. As a consequence, HBT analytical models present a complex formulation, involving many fitting parameters, and a time consuming extraction procedure, which require tedious optimization steps. Black-box table-based models are also time domain approaches but with simpler topologies, mathematical formulations and extraction procedures, since few parameters are involved. Besides, their nonlinear functions are table-based and thus can be applied to different devices and processes. In the published literature, there exist different table-based approaches for FETs, but in the case of HBTs, only mixed analytical/table-based approaches, in which either the nonlinear current or the charge function is analytical. In this thesis work a fully table-based nonlinear model for HBTs, which includes both dynamic thermal and noise modeling, has been developed and validated at device and circuit level. From this model, a Schottky diode table-based model was also developed and improved to account for diode soft-breakdown. This diode model has also been validated at device and circuit level, and used in power probes simulations to study long–term memory effects. Most of the measurements used in this work for models extraction and validation purposes were performed by a using a multi-tone nonlinear measurement system based on Maury-NMDG LSNA, with a microwave bandwidth from 0.6 GHz to 50 GHz , and Low Frequency (LF) bandwidth from 10 KHz to 24 MHz. The proposed HBT table-based model uses four instantaneous table-based nonlinear functions: Ic, Qc, Vbe and Qb, all defined versus Ib and Vce by using a nonuniform grid. Thermal modeling (static and dynamic), which includes both self-biasing and environment temperature dependence, Ta, is formulated by linearly mapping the current table-based functions versus Ta, coupled with explicit thermal feedback. Four table-based nonlinear coefficients are required to predict the device behavior versus ambient temperature. The nonlinear current functions are extracted from DC I-V measurements at one Ta, while the nonlinear thermal coefficients are extracted from DC I-V measurements at three differents Ta. This thermal model has been validated for on-die InGaP/GaAs HBTs, under DC, small and large signal excitations, and it was obtained good model predictions. In order to develop an efficient model for oscillator design, LF noise modeling should be also considered. As a consequence, an extension of the previous HBT model to account for LF effects is also proposed in this thesis work. The noise sources included in the model are of a cyclostationary nature, thus able to account for dynamic noise effects under large-signal conditions. The proposed extended model was validated at device level under DC, small- and large-signal (single and multi-tone) conditions by using commercially packaged SiGe HBTs. For validation purposes at circuit level, several oscillator circuits were also designed and fabricated and predictions of phase noise, oscillation frequency and oscillation power were compare with measurements. In the case of the Schottky diode table-based model proposed, to account for soft breakdown modeling the table-based current function was analytically extended to account for diode behavior under high input RF power drive. This fact is very important to provide accurate predictions in power detector circuits. The model was validated, under different DC and large-signal operating conditions. One of the main applications of the model was to predict power detectors behavior under large-signal single- and two-tone excitations. The results achieved improved on those obtained with the device manufacturer´s model. By using this model, it was demonstrated with simulations, the influence of the detector baseband impedances under two-tone excitation on the detector output voltage. To conclude, the proposed nonlinear HBT and diode table-based models have demonstrated their generality, accuracy and usefulness in the analysis and design of different microwave nonlinear circuits.
YR 2012
FD 2012-05-29
LK http://hdl.handle.net/11093/285
UL http://hdl.handle.net/11093/285
LA eng
DS Investigo
RD 10-sep-2024