The designer's guide to Verilog-AMS

The Verilog Hardware Description Language (Verilog-HDL) has long been the most popular language for describing complex digital hardware. It started life as a prop- etary language but was donated by Cadence Design Systems to the design community to serve as the basis of an open standard. That standard was formalized in 1995 by the IEEE in standard 1364-1995. About that same time a group named Analog Verilog International formed with the intent of proposing extensions to Verilog to support analog and mixed-signal simulation. The first fruits of the labor of that group became available in 1996 when the language definition of Verilog-A was released. Verilog-A was not intended to work directly with Verilog-HDL. Rather it was a language with Similar syntax and related semantics that was intended to model analog systems and be compatible with SPICE-class circuit simulation engines. The first implementation of Verilog-A soon followed: a version from Cadence that ran on their Spectre circuit simulator. As more implementations of Verilog-A became available, the group defining the a- log and mixed-signal extensions to Verilog continued their work, releasing the defi- tion of Verilog-AMS in 2000. Verilog-AMS combines both Verilog-HDL and Verilog-A, and adds additional mixed-signal constructs, providing a hardware description language suitable for analog, digital, and mixed-signal systems. Again, Cadence was first to release an implementation of this new language, in a product named AMS Designer that combines their Verilog and Spectre simulation engines

HIGHLIGHTS IN PHYSICAL SIMULATION AND ANALYSIS AT ICCAD

Six papers were chosen to represent twenty years of research in physical simulation and analysis, three papers addressing the problem of extracting and simulating interconnect effects and three papers describing techniques for simulating steady-state and noise behavior in RF circuits. In this commentary paper we will try to describe the contribution of each paper and place that contribution in some historical context

NONLINEAR CIRCUIT SIMULATION 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 [1] to find the steady-state behavior of analog, RF, and microwave circuits. In particular, frequency-domain simulation eliminates problems from distributed components and high-Q circuits by forgoing a nonlinear differential equation representation of the circuit in favor of a complex algebraic representation. This paper describes the spectral Newton technique for performing simulation of nonlinear circuits in the frequency-domain, and its implementation in Harmonica. Also described are the techniques used by Harmonica to exploit both the structure of the spectral Newton formulation and the characteristics of the circuits that would be typically seen by this type of simulator. These techniques allow Harmonica to be used on much larger circuits than were normally attempted by previous nonlinear frequency-domain simulators, making it suitable for use on Monolithic Microwave Integrated Circuits (MMICs). 1

Efficient Steady-State Analysis based on Matrix-Free Krylov-Subspace Methods

Gaussian-elimination based shooting-Newton methods, a commonly used approach for computing steady-state solutions, grow in computational complexity like N³ where N is the number of circuit equations. Just using iterative methods to solve the shooting-Newton equations results in an algorithm which is still order N because of the cost of calculating the dense sensitivity matrix. Below, a matrix-free Krylov-subspace approach is presented, and the method is shown to reduce shooting-Newton computational complexity to that of ordinary transient analysis. Results from several examples are given to demonstrate that the matrix-free approach is more than ten times faster than using iterative methods alone for circuits with as few as 400 equations

The Designer’s Guide Community downloaded from www.designers-guide.org Simulation and Modeling of Nonlinear Magnetics

Version 1b, August 1994 A procedure for modeling and simulation of arbitrary nonlinear magnetics components is presented. A set of electromagnetic primitives is described as implemented in Verilog-A. The primitives include cores, gaps, and windings that are combined to model ferromagnetic inductors and transformers. The physics of the ferromagnetic core model is described. The model is used to illustrate how to overcome some difficult modelling issues such as hysteresis, incremental models, implicit models, and multidisciplinary model

An almost-periodic Fourier transform for use with harmonic balance

Harmonic balance is a powerful technique for the simulation of mildly nonlinear microwave circuits. This technique has had limited application for tie analysis of almost-periodic circuits, such as mixers, due to the difficulties of transforming waveforms from the time domain to the frequency domain and vice versa. In this paper, a new Fourier transform algorithm for almost-periodic functions (APFT) is developed that is both efficient and accurate. Unlike previous attempts to solve this problem, the new afgorithm does not constmin the input frequencies and uses the theoretically minimum number of time points