Showing papers by "Giorgio Vannini published in 2002"

A modified Volterra series approach for nonlinear dynamic systems modeling

Abstract: This paper describes a modeling approach for nonlinear dynamic systems based on a modified Volterra series; by comparing the truncation error of this series with that of the classical Volterra one, we outlined that, under the assumption of short-term nonlinear memory effects, the modified series enables a single-fold nonlinear convolution integral to be adopted also in the presence of strong nonlinearities. The measurement-based identification of the first terms of the modified Volterra series is described; experimental and simulation results which confirm the theoretical considerations are also provided.

Millimeter-wave FET modeling using on-wafer measurements and EM simulation

Abstract: Electron device modeling is a challenging task at millimeter-wave frequencies. In particular, conventional approaches based on lumped equivalent circuits become inappropriate to describe complex distributed and coupling effects, which may strongly affect the transistor performance. In this paper, an empirical distributed FET model is adopted that can be identified on the basis of conventional S-parameter measurements and electromagnetic simulations of the device layout. The consistency of the proposed approach is confirmed by robust scaling properties, which enable millimeter-wave small-signal S-parameters to be predicted as a function of the device periphery and number of gate fingers. Moreover, it is shown how the model identified on the basis of standard S-parameter measurements up to 50 GHz can be efficiently exploited in order to obtain reasonably accurate small-signal prediction up to 110 GHz. Extensive experimental validation is presented for 0.2-/spl mu/m pseudomorphic high electron-mobility transistors devices.

Accurate prediction of PHEMT intermodulation distortion using the nonlinear discrete convolution model

Abstract: A general-purpose, technology-independent behavioral model is adopted for the intermodulation performance prediction of PHEMT devices. The model can be easily identified since its nonlinear functions are directly related to conventional DC and small-signal differential parameter measurements. Experimental results which confirm the model accuracy at high operating frequencies are provided in the paper.

VCO behavioral modeling based on the nonlinear integral approach

Abstract: This paper presents a new behavioral model for VCO circuits based on a modeling. approach originally adopted for the description of the nonlinear dynamic behavior of electron devices. The new VCO model allows a great accuracy in the description of dynamic nonlinear operations and enables many limitations of existing modelling approaches to be overcome. The computational efficiency and the great accuracy of the model makes it suitable for system-level simulations. Results about the model prediction under small- and large-signal conditions and about its efficiency in comparison with transistor-level simulations are provided in the paper.

Equivalent-voltage approach for modeling low-frequency dispersive effects in microwave FETs

Abstract: In this paper, a simple and efficient approach for the modeling of low-frequency dispersive phenomena in FETs is proposed. The method is based on the definition of a virtual, nondispersive associated device controlled by equivalent port voltages and it is justified on the basis of a physically-consistent, charge-controlled description of the device. Dispersive effects in FETs are accounted for by means of an intuitive circuit solution in the framework of any existing nonlinear dynamic model. The new equivalent-voltage model is identified on the basis of conventional measurements carried out under static and small signal dynamic operating conditions. Nonlinear experimental tests confirm the validity of the proposed approach.

A computationally efficient approach for the design of RF power amplifiers

Abstract: A computationally efficient procedure for the design of RF power amplifiers is presented. The proposed approach allows for the identification of "near-optimal" source and load terminations of the amplifier stage providing maximum output power under assigned linearity, minimum gain and other possible constraints. The design procedure is completely based on closed form numerical computations, without requiring non linear optimisations as normally happens in standard design approaches. A single-stage 2.4 GHz amplifier prototype has been designed and manufactured in Silicon BJT MMIC technology, according to the criteria provided by the new methodology. Experimental results are in good agreement with simulations and confirm the validity of the proposed approach.

Circuit Architectures for Low-Phase-Noise Oscillators

Abstract: In this paper some considerations on different oscillator topologies are presented with the aim of analyzing their behavior in terms of phase noise performance. In particular, our analysis suggests that a 9db improvement in the phase noise level can be obtained when using a “Push-Push” oscillator architecture in comparison with a fundamental-frequency oscillator developed under the same conditions. Simulations of different oscillator topologies, which confirm the proposed theory, are shown in the paper.

Power amplifier ACPR simulation using standard harmonic balance tools

Abstract: The adoption of complex digital modulation techniques in wireless communication systems has posed a great demand on RF and microwave power amplifier performance. When high linearity is required, the amplifier characterization is based on intermodulation or, more commonly, on Adjacent Channel Power Ratio (ACPR) and other parameters more directly related to the actual circuit operation. In this paper a previously proposed Harmonic Balance (HB) algorithm is adopted for the ACPR simulation of power amplifiers excited by digitally modulated signals. With respect to other approaches the proposed technique provides fast and accurate results using a conventional HB engine without requiring special purpose algorithms.