\chapter{Library of cable models, MOD} \label{structure_of_MOD}

MOD comprises the library of cable models; the library contains the following:

\begin{enumerate}
\item Models of individual cables which are created by the cable model building process or delivered as elements of the library. These models may be used as input to the cable bundle model building process.

\item Models of cable bundles which are created by the cable bundle model building process and may be used as input to the Spice cable bundle model building process. 
\item Spice models of specific cable bundle modelling configurations including length, incident field excitation, transfer impedance coupling and target Spice version. These models will have an accompanying symbol corresponding to the target Spice version and are created by the Spice cable bundle model building process. These models may then be included in appropriate versions of Spice. 

\end{enumerate}

The library of cable models is a hierarchical structure, this structure reflects the manner in which the elements which go to create a Spice cable bundle model are combined.

The library contains a directory of individual cable models ( \textbf{CABLE} ) e.g. single conductors, twisted pairs, coaxial cables, shielded twisted pairs etc. These cable models may be combined in any configuration, along with ground plane and overshield specifications to form a cable bundle model. A cable bundle model contains all the information required to characterise a particular bundle configuration. Cable bundle models are kept in the directory \textbf{BUNDLE}. Cable bundle models are identified by a name provided by the user. A cable bundle may be applied in a range of modelling scenarios, each requiring a separate Spice model due to differences in configuration (cable bundle length incident field excitation, transfer impedance coupling models included, and their coupling direction etc.) Each of the cable bundle models within the \textbf{BUNDLE} directory can therefore be used as the basis of a number of Spice cable bundle models. These Spice cable bundle models may be kept in the \textbf{SPICE} directory within MOD. This directory also contains a sub-directory \textbf{SYMBOL} containing the circuit symbols for the Spice cable bundle models. These circuit symbols may be exported to the appropriate place for use with gschem or LTspice as described in chapter \ref{using_models_in_spice}.

The software can produce Spice sub-circuit models of transmission lines for three versions of Spice:

\begin{enumerate}
\item Ngspice
\item LTspice

\item PSpice 

\end{enumerate}

The file formats for the three Spice versions differ so MOD can contain up to three different versions of the same Spice subcircuit model.

%An example of the library of cable models generated in the running of the test cases is shown in figure \ref{fig:MOD_structure} below.
%
%%Include MOD structure figure here 
%
%\begin{figure}[h]
%\centering
%\includegraphics[scale=0.5]{./Imgs/MOD_picture.jpg}
%\caption{Structure of the library of cable models (MOD)}
%\label{fig:MOD_structure}
%\end{figure}
%
%\section{Example of a Library of cable models}
%
%%Include directory structure of MOD for the validation test cases here with notes.
%%The picture is obtained with the unix command `tree --charset=ascii MOD' run from the TEST_CASES directory 
%
%
%An example of the library of cable models generated in the running of the test cases is shown in figure \ref{fig:MOD_structure} below.
%
%\begin{verbatim}
%MOD
%|-- BUNDLE_MODELS
%|   |-- 2_wire
%|   |   |-- 2_wire_ac.lib
%|   |   `-- 2_wire_trans.lib
%|   |-- 2_wire.bundle
%|   |-- two_wires_over_ground.bundle
%|   |-- wire_over_ground
%|   |   `-- wire_over_ground_ac.lib
%|   `-- wire_over_ground.bundle
%`-- CABLE_MODELS
%    `-- single_wire.cable
%\end{verbatim}
%
%
%\section{Using MOD with different Spice versions}
%
%The software can produce Spice sub-circuit models of transmission lines for three versions of Spice:
%\begin{enumerate}
%\item Ngspice
%\item LTspice
%\item PSpice 
%\end{enumerate}
%
%The file formats for the three Spice versions differ so MOD can contain up to three different versions of the same Spice subcircuit model.

\cleardoublepage