We review some usual laser range finding techniques for in- dustrial applications. After outlining the basic principles of triangulation and time of flight (pulsed, phase-shift and frequency modulated continu- ous wave (FMCW)), we discuss their respective fundamental limitations. Selected examples of traditional and new applications are also briefly presented. © 2001 Society of Photo-Optical Instrumentation Engineers.

Laser ranging: a critical review of usual techniques for distance measurement

The frequency-dependent characteristics of the microstrip discontinuities have previously been analyzed using full-wave approaches. The time-domain finite-difference (TD-FD) method presented here is an independent approach and is relatively new in its application for obtaining the frequency-domain results for microwave components. The validity of the TD-FD method in modeling circuit components for MMIC CAD applications is established. >

Time-domain finite difference approach to the calculation of the frequency-dependent characteristics of microstrip discontinuities

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 (HEMT's) and metal semiconductor field-effect transistor (MESFET's). 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.

Extensions of the Chalmers nonlinear HEMT and MESFET model

A new small-signal modeling approach applied to GaN-based devices is presented. In this approach, a new method for extracting the parasitic elements of the GaN device is developed. This method is based on two steps, which are: 1) using cold S-parameter measurements, high-quality starting values for the extrinsic parameters that would place the extraction close to the global minimum of the objective function for the distributed equivalent circuit model are generated and 2) the optimal model parameter values are searched through optimization using the starting values already obtained. The bias-dependent intrinsic parameter extraction procedure is improved for optimal extraction. The validity of the developed modeling approach and the proposed small-signal model is verified by comparing the simulated wide-band small-signal S-parameter, over a wide bias range, with measured data of a 0.5-/spl mu/m GaN high electron-mobility transistor with a 2/spl times/50 /spl mu/m gatewidth.

A new small-signal modeling approach applied to GaN devices

Publisher Summary This chapter deals with the models currently used to improve the quasistatic approximation of microstrip structures. The chapter presents a brief review of the microstrip fundamentals; a comprehensive account of these dynamical models. A particular model based on the calculation of the electric surface currents in the structure is introduced in the chapter. The Green's functions involved are constructed and numerically evaluated using the exact formulation for dipole potentials in a stratified medium. New evaluation techniques developed for Sommerfeld integrals permit a very accurate computation of Green's functions. Their properties are then extensively discussed; the validity of the quasistatic approximations is checked and the importance of the surface wave is pointed out in detail. Finally, the integral equations for the currents are set up and solved by numerical methods in that also give several practical applications. The chapter concludes the model is that the surface currents on the antenna are directly determined and the near field can then be determined easily, that becomes most important when microstrip structures are utilized as radiators or biological applicators.

A Dynamical Radiation Model for Microstrip Structures

A planar waveguide model with a frequency-dependent effective relative permittivity and a frequency-dependent effective width is developed for the open microstrip line. The validity of this waveguide model is shown by experimental results from measurements with a resonator and a sliding-load technique.

Planar waveguide model for calculating microstrip components

In this paper, an accurate table-based large-signal model for AlGaN/GaN HEMTs accounting for trapping- and self-heating-induced current dispersion is presented. The B-spline-approximation technique is used for the model-element construction, which improves the intermodulation-distortion (IMD) simulation. The dynamic behavior of the trapping and self-heating processes is taken into account in the implementation of the model. The model validity is verified by comparing the simulated and measured outputs of the device tested under pulsed and continuous large-signal excitations for devices of 1-mm gate width. Single- and two-tone simulation results show that the model can efficiently predict the output power and its harmonics and the associated IMD under different input-power and bias conditions.

Large-Signal Model for AlGaN/GaN HEMTs Accurately Predicts Trapping- and Self-Heating-Induced Dispersion and Intermodulation Distortion

A new optimization formulation is presented for efficient FET model parameter extraction, in which data-fitting is carried out in multi reference planes instead of only one, and the objective function is minimized by a bidirectional search technique. As an example of application, all parameters of a commonly used 15-element small-signal FET equivalent circuit model are clearly identified from only one set of measured S-parameters. A self-consistent generation of starting values can be involved regarding the FET in the passive pinch-off operating mode. Moreover, applying multi-bias data-fitting, which is performed without increasing the number of ordinary optimization variables, yields a robust determination of both the overall bias-independent parasitics and the bias-dependent intrinsic elements. For demonstration results are presented for a 0.5-/spl mu/m MESFET. >

FET model parameter extraction based on optimization with multiplane data-fitting and bidirectional search-a new concept

A method for calculating microstrip discontinuities and T junctions is described, and a waveguide model for the microstrip line is defined. With the help of this model and the use of an orthogonal series expansion, a solution of the above problems is found. Numerical results for the scattering matrices of both the discontinuities and the junctions are given.

Gunter Kompa

Papers

A new small-signal modeling approach applied to GaN devices

Planar waveguide model for calculating microstrip components

Large-Signal Model for AlGaN/GaN HEMTs Accurately Predicts Trapping- and Self-Heating-Induced Dispersion and Intermodulation Distortion

FET model parameter extraction based on optimization with multiplane data-fitting and bidirectional search-a new concept

Calculation method for microstrip discontinuities and T junctions