![]() ![]() One disadvantage of this approach, is the obvious one, in that the time to implement a new model increases disproportionately with increasing model complexity. Models based on hand written C++ code are normally restricted to basic devices that form the fundamental component core of a simulator - particularly where simulation computational efficiency is important. At the time of writing these notes the latest device to be added to Qucs using this approach is the exponential pulse source 4. Obviously, this does require a specialised knowledge of the Qucs model programming interface 2, the necessary C++ skills, including a good working knowledge of the Trolltech Qt toolkit 3. This fundamental route involves hand coding the C++ code for a new model 1, its compilation and linking with the core Qucs C++ code. The first of these has been used extensively by the package developers to construct the built-in models that are distributed with each Qucs release. When Qucs 1ģ was first released only two of these were available for users to develop new device models. The diagram is structured as a flow chart which emphasises the different device modelling routes. 1 is a block diagram of the analogue component modelling and simulation facilities currently provided by the Qucs package. From a users point of view component models are the key to simulator productivity the greater the number of different models the easier it becomes to analyse mixed analogue and digital electronic systems. Without component models the science of circuit simulation would not have developed to the stage it has today. All circuit simulators have one other important attribute, namely that they represent individual electronic components by a model, or abstraction, in a way that can be understood and analysed by the simulation engine when undertaking a simulation task. Most circuit simulators have a number of common basic attributes firstly circuits are represented by a textual netlist or a schematic diagram which contains all the information required by a simulator to analyse the performance of a circuit, and secondly a simulation engine which undertakes the calculation of circuit performance in one or more different circuit domains such as DC, AC or transient, and thirdly a post simulation processing system which structures and displays the simulation data in both tabular and graphical forms. Qucs electronic device and circuit modelling Circuit simulation packages are complex software systems which often take years to mature to a stage where they are capable of analysing the current generation of integrated and discrete electronic circuits. The text includes a number of illustrative examples for readers to try and experiment with. The aim of this tutorial note is to outline the background to these important package extensions and to provide real help to Qucs users who are interested in writing and experimenting with their own models. Much of these new aspects have up to now been undocumented and are likely to be very new to most Qucs users. In designing the latest Qucs modelling features the Qucs team has made a central focus of their work the need to provide the package with an interactive and easy to use modelling system which allows fast model prototype construction. Release.12 extends these features to add model development using symbolic equations that are similar to compact device code written in the Verilog- A modelling language. ![]() Release.11 introduced component values defined by equations and for the first time allowed subcircuits with parameters. ![]() A copy of the license is included in the section entitled GNU Free Documentation License.Ģ Introduction Qucs releases.11 and.12 mark a turning point in the development of the Qucs component and circuit modelling facilities. 1 Qucs A Tutorial Component, compact device and circuit modelling using symbolic equations Mike Brinson Copyright c 27 Mike Brinson Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation. ![]()
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