Carlo Naldi

Bio: Carlo Naldi is an academic researcher from Polytechnic University of Turin. The author has contributed to research in topics: MESFET & Monolithic microwave integrated circuit. The author has an hindex of 12, co-authored 42 publications receiving 1029 citations.

Coplanar Waveguides for MMIC Applications: Effect of Upper Shielding, Conductor Backing, Finite-Extent Ground Planes, and Line-to-Line Coupling

Abstract: Parasitic effects occurring in actual realizations of coplanar waveguides (CPW) for microwave integrated circuits on GaAs substrates, such as the influence of an upper shield, conductor backing, finite-extent ground planes, and line-to-line coupling, are discussed and evaluated. CAD-oriented analytical expressions are obtained for the electrical quasi-TEM parameters of the relevant waveguiding structures by means of exact or approximate conformal mapping techniques. Differences in electrical behavior with respect to ideal CPW's are highlighted, and practical design criteria are obtained for keeping cover height, ground-plane width, and line-to-line spacing effects to a minimum.

Analytical formulas for coplanar lines in hybrid and monolithic MICs

Abstract: Some analytical formulas for the parameters of coplanar lines are discussed and validated; a chart is given for the design of coplanar waveguides on GaAs. The formulas discussed here, together with those presented previously by us (1983) represent a suitable set for the design of coplanar lines for hybrid and monolithic MICs (microwave integrated circuits).

Parameters of coplanar waveguides with lower ground plane

Abstract: A new analytical expression for the impedance and the permittivity of coplanar waveguides with lower ground plane is presented. Although approximate in principle, this expression shows very good agreement with the upper or lower bounds of the parameters, computed via a spectral-domain variational approach.

Physics-based electron device modelling and computer-aided MMIC design

Abstract: On overview on the state of the art and future trends in physics-based electron device modelling for the computer-aided design of monolithic microwave ICs is provided. After a review of the main physics-based approaches to microwave modeling, special emphasis is placed on innovative developments relevant to circuit-oriented device performance assessment, such as efficient physics-based noise and parametric sensitivity analysis. The use of state-of-the-art physics-based analytical or numerical models for circuit analysis is discussed, with particular attention to the role of intermediate behavioral models in linking multidimensional device simulators with circuit analysis tools. Finally, the model requirements for yield-driven MMIC design are discussed, with the aim of pointing out the advantages of physics-based statistical device modeling; the possible use of computationally efficient approaches based on device sensitivity analysis for yield optimization is also considered. >

Simulation and Design of Microwave Class-C Amplifiers through Harmonic Analysis

Abstract: A method for analyzing microwave class-C amplifiers is proposed which satisfies the requirements of a wide application field, and, at the same time, operates with a fast runing time and without convergence problems. It is based on the partitioning of the circuit into linear and nonlinear subnetworks for which, respectively, frequency-domain and time-domain equations are written. Then, taking into account that the time-domain and frequency-domain representations are related by the Fourier series, the circuit behavior is described by means of a system of nonlinear equations whose unknowns are the harmonic components of the incident waves at all the connections. To overcome the numerical problems arising in the search for the solution of this system when strong nonlinearities are involved, a special step-by-step procedure is adopted. The problem is transformed into the search for the solution of a sequence of well-conditioned systems of equations corresponding to a sequence of well-chosen circuits obtained from the original one through progressive changes of the input signal starting from 0 up to the nominal value. The program which implements the method is also described and the results of the analysis relative to a class-C amplifier are compared with measured values.

CAD models for multilayered substrate interdigital capacitors

Abstract: Conformal mapping-based models are given for interdigital capacitors on substrates with a thin superstrate and/or covering dielectric film. The models are useful for a wide range of dielectric constants and layer thicknesses. Capacitors with finger numbers n/spl ges/2 are discussed. The finger widths and spacing between them may be different. The results are compared with the available data and some examples are given to demonstrate the potential of the models.

Analytical evaluation of the interdigital electrodes capacitance for a multi-layered structure

Abstract: The widespread use of interdigital electrodes in such applications as microwave filters, surface acoustic wave devices, electro-optic shutters as well as on chemical and biological sensing and even on the electrical and dielectric characterization of materials requires that we improve our description of their electrical performance. In this paper, we present new analytical expressions for the capacitance between the two comb electrodes of a periodic interdigital capacitive sensor, based on conformal mapping techniques. This proposed model is general and quite independent of the particular application and can be applied for any space and finger width as well as for any number of layers with different thickness and permittivity. The capacitance for a particular sensor configuration is a function of the dielectric permittivity of the materials, the fingers length and of two geometric non-dimensional parameters: (i) the ratio between the space and finger widths; (ii) the ratio between the thickness of the sensitive layer and the spatial sensor wavelength. Comparisons with previously published models as well as with experimental data and finite element analysis were made.

Simulation of Nonlinear Circuits in the Frequency Domain

Abstract: Simulation in the frequency domain avoids many of the severe problems experienced when trying to use traditional time-domain simulators such as SPICE to find the steady-state behavior of analog and microwave circuits. In particular, frequency-domain simulation eliminates problems from distributed components and high-Q circuits by foregoing a nonlinear differential equation representation of the circuit in favor of a complex algebraic representation. This paper reviews the method of harmonic balance as a general approach to converting a set of differential equations into a nonlinear algebraic system of equations that can be solved for the periodic steady-state solution of the original differential equations. Three different techniques are applied to solve the algebraic system of equations: optimization, relaxation, and Newton's method. The implementation of the algorithm resulting from the combination of Newton's method with harmonic balance is described. Several new ways of exploiting both the structure of the formulation and the characteristics of the circuits that would typically be seen by this type of simulator are presented. These techniques dramatically reduce the time required for a simulation, and allow harmonic balance to be applied to much larger circuits than were previously attempted, making it suitable for use on monolithic microwave integrated circuits (MMIC's).

Coplanar Waveguides for MMIC Applications: Effect of Upper Shielding, Conductor Backing, Finite-Extent Ground Planes, and Line-to-Line Coupling

Abstract: Parasitic effects occurring in actual realizations of coplanar waveguides (CPW) for microwave integrated circuits on GaAs substrates, such as the influence of an upper shield, conductor backing, finite-extent ground planes, and line-to-line coupling, are discussed and evaluated. CAD-oriented analytical expressions are obtained for the electrical quasi-TEM parameters of the relevant waveguiding structures by means of exact or approximate conformal mapping techniques. Differences in electrical behavior with respect to ideal CPW's are highlighted, and practical design criteria are obtained for keeping cover height, ground-plane width, and line-to-line spacing effects to a minimum.

Quasi-TEM description of MMIC coplanar lines including conductor-loss effects

Abstract: A quasi-TEM model of MMIC coplanar structures is presented. The elements of the distributed equivalent circuit are calculated by closed-form approximations and hence can easily be implemented into CAD packages. The effects of nonideal conductors are included as well as substrate loss and finite metallization thickness. The description holds for the entire quasi-TEM range, i.e. for typical MMIC geometries from DC to millimeter-wave frequencies. The validity of the model was checked by comparison to full-wave results. The errors for the effective dielectric constant and the characteristic impedance range below 5% for the attenuation typical values of 5-10% are found (maximum: 20%). >