A large-signal analysis of broad-band klystrons with design applications

For the design of a high-performance broad-band klystron, an accurate large-signal analysis is made. By a one-dimensional analysis program using a disk model of the electron stream, the interaction between a bunched electron beam and the electric field in each cavity gap is studied, taking into consideration space-charge forces, relativistic effects, and electric field distributions in ungridded gaps; beam loading is included by an iterative method at each intermediate gap, and the energy exchange in the output gap is obtained from the change in kinetic energy. On the five-cavity UHF-TV klystron designed with this program and having a conversion efficiency of over 60 percent, the debunching effect of the electric field in intermediate cavity gaps and the behavior of vibrating electrons in the output gap are clarified. Calculated conversion efficiency is shown to agree well with measured efficiency over the pass-band. Additionally, by a two-dimensional analysis program, the effect of the cathode magnetic coefficient on the electron bunching is studied.     

A nonquasi-static MOSFET model for SPICE-transient analysis

The long-channel MOSFET model is based on an approximate solution to the nonlinear current-continuity equation in the channel. The model includes the large-signal transient and the small-signal AC analyses, although only the transient model is reported here. Comparisons have been made between this model and the 1-D numerical solution to the current-continuity equation, 2-D device simulation (PISCES), and the quasistatic (QS) results. The channel-charge partitioning scheme in the charge-based QS models is shown to be inadequate for the fast transient. This model does not use a charge-partitioning scheme and the currents are dependent on the history of the terminal voltages, not just the instantaneous voltages and their derivatives. For the slow signals (compared to the channel transit time), the nonquasistatic (NQS) model is reduced to the quasistatic 40/60 channel-charge partitioning scheme. The CPU time required for this model is about two to three times longer than that of conventional MOSFET models in SPICE     

A nonquasi-static table-based small-signal model of heterojunction bipolar transistor

A nonquasi-static table-based (NQS-TB) small-signal model, which has been used successfully in modeling FETs, is applied to a heterojunction bipolar transistor (HBT). The capacitive couplings associated with base cause the conventional model to be invalid at high frequencies. To take these effects into account, a new model is proposed that is compatible with a small-signal T-model topology. We demonstrate good agreement between the measured and simulated S-parameters over the range of 1-40 GHz.     

A new empirical large-signal HEMT model

We propose an empirical large-signal model of high electron mobility transistors (HEMTs). The bias-dependent data of small-signal equivalent circuit elements are obtained from S-parameters measured at various bias settings. And C_gs, C_gd, g_m, and g_ds, are described as functions of V_gs and V_ds. We included our large-signal model in a commercially available circuit simulator as a user-defined model and designed a 30/60-GHz frequency doubler. The fabricated doubler's characteristics agreed well with the design calculations     

A pseudomorphic AlGaAs/n+-InGaAs metal-insulator-dopedchannel FET for broad-band, large-signal applications

Molecular beam epitaxy (MBE)-grown L_g=1.7-μm pseudomorphic Al_0.38Ga_0.62As/n⁺-In_0.15Ga _0.85As metal-insulator-doped channel FETs (MIDFETs) are presented that display extremely broad plateaus in both f_T and f_max versus V_GS, with f_T sustaining 90% of its peak over a gate swing of 2.6 V. Drain current is highly linear with V_GS over this swing, reaching 514 mA/mm. No frequency dispersion in g _m up to 3 GHz was found, indicating the absence of electrically active traps in the undoped AlGaAs pseudoinsulator layer. These properties combine to make the pseudomorphic MIDFET highly suited to linear, large-signal, broadband applications     

A quasi-three-dimensional large-signal dynamic model of distributedfeedback lasers

A simple, but powerful, quasi-three-dimensional large-signal dynamic model of distributed feedback semiconductor laser is presented. The transient response of lasers is analyzed by using a combined beam propagation method and time-domain algorithm that is capable of including the longitudinal and lateral variation of the optical-mode and carrier density profiles. In addition, the spontaneous emission noise, the nonuniform current injection resulting from the variation of Fermi-voltage as well as that of the refractive index distribution are also taken into consideration. Using this model, the influence of nonuniform waveguide structure on the static and dynamic responses of distributed feedback lasers is analyzed. In addition, a novel double tapered waveguide distributed feedback laser is proposed for stable single-mode operation at high power     

A large-signal HSPICE model for the heterojunction bipolartransistor

The development of an accurate nonlinear HSPICE model for a 3-×10-μm² heterojunction bipolar transistor (HBT) is described. The model allows the simulation of nonlinear measurements such as gain at the 1-dB compression point (P_{1 dB}) and third-order intercept point. Experimental data characterizing an HBT at 12.5 GHz are presented, demonstrating the validity of the model for MMIC chip designs     

A large-signal switching MESFET model for intermodulationdistortion analysis

This paper describes an improved large-signal model for predicting an intermodulation distortion (IMD) power characteristic of MESFETs in switching applications. The model is capable of modeling the voltage-dependent drain current and its derivatives, including gate-source and gate-drain capacitors. The drain current and its derivatives are described by a function of a voltage-dependent drain conductance. The model parameters are extracted from a measured drain conductance versus gate voltage characteristic of a MESFET. This paper also presents a new fully symmetric equivalent circuit for switching MESFETs. The IMD power characteristics calculated with the use of the proposed method are compared with experimental data taken from a monolithic microwave integrated circuit single-pole double-throw switch. Good agreements over the large gate voltages and input power levels are observed     

Improved large-signal quasistatic MESFET model

Improvements to the quasistatic modelling procedure which has been established by Rauscher and Willing (1978, 1979) are discussed. Specifically, a more accurate method of modelling the channel conductance and a technique for establishing the correct DC bias conditions within the MESFET model are provided.<>     

IMPATT diode quasi-static large-signal model

A quasi-static large-signal model of an IMPATT diode with general doping profile is derived. The numerical solution of this model has been implemented in a Fortran IV program which executes economically. This model has been used to analyze large-and small-signal admittances of GaAs double-drift and quasi-Read IMPATT diodes. The small-signal results are in good agreement with calculations done using a linearized small-signal model. The large-signal calculations exhibit power and efficiency saturation when reasonable values of parasitic resistance are included and are in good agreement with experimental GaAs diode performance. The generalized quasi-static formulation simplifies analysis of IMPATT structures with arbitrary doping profiles, specifically those with distributed avalanche zones, by providing the correspondence between these devices and the Read diode model.     

A large-signal, analytic model for the GaAs MESFET

An analytic, large-signal model for the GaAs MESFET is presented. The device model is physics-based and describes the conduction and displacement currents of the FET as a function of instantaneous terminal voltages and their time derivatives. The model allows arbitrary doping profiles in the channel and is thus suitable for the optimization of ion-implanted and buried-channel FETs. It also accounts for charge accumulation in the conducting channel at high electric fields and the associated capacitance in a self-consistent manner. Theoretical predictions of the model are correlated with experimental data on X -band power FETs and excellent agreement is obtained     

A large-signal SOI MOSFET model including dynamic self-heatingbased on small-signal model parameters

A new technique for a large-signal SOI MOSFET model with self-heating is proposed, based on thermal and electrical parameters extracted by fitting a small-signal model to measured s-parameters. A thermal derivative approach is developed to calculate the thermal resistance when the isothermal dc drain conductance is extracted from small-signal fitting. The thermal resistance is used to convert the measured dc current-voltage (I-V) characteristics containing the self-heating effects to the isothermal I-V characteristics needed for the large-signal model. Large-signal pulse and sinusoidal input signals are used to verify the model by measurement, and shown to reproduce the observed large-signal behavior of the devices with great accuracy, especially when two or more thermal time constants are used     

An efficient CAD-oriented large-signal MOSFET model

An efficient computer-aided-design-oriented large-signal microwave model for silicon MOSFETs is presented based on the well-founded small-signal equivalent circuit including self-heating effect and charge conservation condition. The proposed new single continuously differentiable empirical equations for drain current and gate capacitance are simple and quite accurate. The model parameters in the equations are constructed in such a way that they can be easily and straightforwardly extracted from measured data. The temperature effect is predicted by simply adopting the linear temperature-dependent model parameters for threshold voltage, saturation current, capacitance, and series resistances. The presented model is a good compromise between the simplicity of numerical calculations and the accuracy of final results that is desired by circuit designers in nonlinear circuit simulation     

A large-signal equivalent circuit model for substrate-induceddrain-lag phenomena in HJFETs

A large-signal HJFET model is developed for drain-lag phenomena caused by deep traps beneath the channel. The model is based on the self-backgating and Shockley-Read-Hall (SRH) statistics. It is shown by two-dimensional (2D) device simulation that electron capture in deep traps is much faster than electron emission under large-signal conditions; therefore, drain current exhibits different responses for rising and falling steps of applied voltage. In the circuit model, electron capture and emission in deep traps are expressed by a parallel circuit consisting of a diode and a resistor, which are physically deduced from SRH statistics. The model agrees well with the 2D simulation results and experimental current-transient data for large-signal voltage steps. In addition, this model accurately describes small-signal drain-conductance dispersion and temperature effects on the trapping phenomena     

A large-signal physical MESFET model for computer-aided design andits applications

A quasi-static, large-signal MESFET circuit model is presented. It is based on a comprehensive quasi-two-dimensional, semiclassical, physical device simulation, and its unique formulation and efficiency make it suitable for the computer-aided design of nonlinear MESFET subsystems. Using this approach the semiconductor equations are reduced to a consistent one-dimensional approximation requiring substantially less computing resources than a full two-dimensional simulation. CPU time is typically reduced by a factor of 1000. A single/two-tone harmonic balance analysis procedure which uses the describing frequency concept is also developed and combined with the MESFET model. Numerical load-pull contours as well as intermodulation distortion contours have been simulated; their comparison with measured results validates the approach taken     

A broad-band transmission line model for a rectangular microstripantenna

A method is developed using the transmission line model to predict the input characteristics of rectangular microstrip antennas over a wide band of frequencies. A series combination of transmission lines is used to represent each transverse magnetic (TM) model. Following a brief summary of the basic transmission line model, the idea of an equivalent length, width, and feed offset are introduced to model each mode. The results predicted by the model compared well with experimental results that assumed varying feed positions. The concept of equivalent length, width, and feed offset was validated by experimental results but shows that the equivalent offset term needs some improvement. The number of modes incorporated in the model depends on the frequency range over which the antenna must be modeled. Using three transmission lines gives good results up to the frequency at which the TM₀₂ mode is excited     

A transfer matrix method based large-signal dynamic model formultielectrode DFB lasers

A large-signal dynamic model capable of modeling the transient behavior of the output power and wavelength of multielectrode DFB lasers is described here. The key feature of the model is the use of a modified form of the transfer matrix method resulting in a time-dependent implementation of this technique. Other features are the inclusion of longitudinal spatial hole burning and nonlinear gain in the model. The versatility of the model is demonstrated in an analysis of the response of a two-electrode DFB laser under large-signal direct current modulation which illustrates the important role played by longitudinal spatial hole burning. The limited use of wavelength tunability in controlling chirp is also demonstrated. However, a scheme to improve the damping mechanism through nonuniform excitation called backbiasing is proposed. Finally, wavelength switching is demonstrated using the model     

Averaged large-signal model of quantum series-parallel resonantconverter

An averaged large-signal model of the quantum series-parallel resonant converter operating in continuous conduction mode is developed and verified using cycle-by-cycle simulations. The model can be used to both derive simple design tools under steady-state conditions and predict large-signal transient responses by using any modern circuit simulator