Efficient generation of X-parameters transistor models by sequential sampling

This letter proposes a sequential sampling technique to generate efficiently multidimensional X-parameters models for microwave transistors, while guaranteeing X-parameters' validity and overcoming simulator convergence issues. The sequential sampling process selects a set of samples that are subsequently used to construct behavioral models with radial basis functions. The proposed method was compared with a tabular X-parameters model with cubic spline interpolation. The radial basis function models demonstrate very fast convergence and greater accuracy already for a few tens of samples. The proposed technique is illustrated for a GaAs HEMT using Curtice3 and Chalmers empirical model simulations as the data source

A Calibrated Time Domain Envelope Measurement System for the Behavioral Modeling of Power Amplifiers

This paper presents a set-up which enables the generation and the calibrated time domain measurements of complex envelopes of modulated signals at both ports of non linear microwave power amplifiers. The architecture of the characterization tool is given. Examples of error corrected time domain envelopes at the input / output RF ports of a 36 dBm output power – 30dB power gain L-band SSPA are shown. Futhermore, the use of this characterization tool and a suitable processing of measurement data are applied to a novel measurement based behavioral modeling approach of non linear devices accounting for memory effects

When self-consistency makes a difference

Compound semiconductor power RF and microwave device modeling requires, in many cases, the use of selfconsistent electrothermal equivalent circuits. The slow thermal dynamics and the thermal nonlinearity should be accurately included in the model; otherwise, some response features subtly related to the detailed frequency behavior of the slow thermal dynamics would be inaccurately reproduced or completely distorted. In this contribution we show two examples, concerning current collapse in HBTs and modeling of IMPs in GaN HEMTs. Accurate thermal modeling is proved to be be made compatible with circuit-oriented CAD tools through a proper choice of system-level approximations; in the discussion we exploit a Wiener approach, but of course the strategy should be tailored to the specific problem under consideratio

Stretching the design: extending analytical circuit design from the linear to the nonlinear domain

In the design of most electronic circuits and systems, designers use computer-aided design (CAD) tools to guide the design flow. They exploit the ability of CAD tools to perform algebraic operations to compute/ predict circuit and system performance. This is possible because, in most electronic circuits and systems, linear operation can be assumed. The behavior of microwave components, circuits, and systems can, for example, be described in terms of "behavioral" parameters, such as Z-parameters, Y-parameters, and S-parameters. Transformation from one parameter to another is achieved by simple linear algebraic operations [1]. The performance of more complex circuits can be computed via linear matrix operations using the relevant parameters, i.e., Y-parameters for parallel connections and Z-parameters for series connections. More significantly, performance predictions can also be obtained via linear algebra transformations, i.e., the maximum gain, minimum noise figure, potential instability, etc., along with design insight, i.e., gain circles, noise circles, optimum input/output match requirements, and so on [1], [2].Ministerio de Ciencia e Innovación | Ref. TEC2011-29264-C03-03Ministerio de Ciencia e Innovación | Ref. TEC2011-28683-C02-0

Automated microwave device characterization set-up based on a technology-independent generalized Bias System

In this paper an automated laboratory set-up for the characterization of micro- and millimeter-wave electron devices under DC, small- and large-signal operation is described, which is based on a generalized, technology-independent bias system. The biasing parameters adopted, which are a linear combination between currents and voltages at the device ports, allow for a complete characterization of the desired empirical data (e.g. multi-frequency S-matrix) throughout all the regions in which the quiescent operation of the device can be conventionally divided, without any need for the switch between different biasing strategies. The look-up tables of experimental data obtained, which are carried out homogeneously with respect to the same couple of bias parameters, independently of the quiescent regions investigated, are particularly suitable for the characterization of empirical non-linear dynamic models for the electron device

LC-VCO design optimization methodology based on the gm/ID ratio for nanometer CMOS technologies

In this paper, an LC voltage-controlled oscillator (LC-VCO) design optimization methodology based on the gm/ID technique and on the exploration of all inversion regions of the MOS transistor (MOST) is presented. An in-depth study of the compromises between phase noise and current consumption permits optimization of the design for given specifications. Semiempirical models of MOSTs and inductors, obtained by simulation, jointly with analytical phase noise models, allow to get a design space map where the design tradeoffs are easily identified. Four LC-VCO designs in different inversion regions in a 90-nm CMOS process are obtained with the proposed methodology and verified with electrical simulations. Finally, the implementation and measurements are presented for a 2.4-GHz VCO operating in moderate inversion. The designed VCO draws 440 μA from a 1.2-V power supply and presents a phase noise of -106.2 dBc/Hz at 400 kHz from the carrier

Ultra-low Voltage Digital Circuits and Extreme Temperature Electronics Design

Certain applications require digital electronics to operate under extreme conditions e.g., large swings in ambient temperature, very low supply voltage, high radiation. Such applications include sensor networks, wearable electronics, unmanned aerial vehicles, spacecraft, and energyharvesting systems. This dissertation splits into two projects that study digital electronics supplied by ultra-low voltages and build an electronic system for extreme temperatures. The first project introduces techniques that improve circuit reliability at deep subthreshold voltages as well as determine the minimum required supply voltage. These techniques address digital electronic design at several levels: the physical process, gate design, and system architecture. This dissertation analyzes a silicon-on-insulator process, Schmitt-trigger gate design, and asynchronous logic at supply voltages lower than 100 millivolts. The second project describes construction of a sensor digital controller for the lunar environment. Parts of the digital controller are an asynchronous 8031 microprocessor that is compatible with synchronous logic, memory with error detection and correction, and a robust network interface. The digitial sensor ASIC is fabricated on a silicon-germanium process and built with cells optimized for extreme temperatures