Twisted_pairs.tex
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\chapter{Twisted Pair cable models}
Twisted pair models have been developed with gauges 20, 22, 24, from 3 different standards \cite{3901/019}, \cite{3901/002} and \cite{3901/025} i.e. 9 models in total.
The process followed to obtain the parameters for the \textbf{.cable\_spec} file from information in the ESCC specifications is as follows (where we assume that all dimensions are converted to metres):
\begin{enumerate}
\item
\begin{equation}
comnductor\_radius = \sqrt{\frac{nominal\_section}{\pi}}
\end{equation}
\item
\begin{equation}
dielectric\_radius = \frac{core\_max\_diameter}{2}
\end{equation}
\item
\begin{equation}
conductor\_separation = finished\_wire\_diameter -2* dielectric\_radius
\end{equation}
\item
The conductor in the model is a homogeneous cylindrical conductor so we need an effective
conductivity. This is based on the maximum resistance (quoted in ohms/km)
\begin{equation}
Conductivity = \frac{length}{(max\_resistance*nominal\_section)}
\end{equation}
\item
The dielectric surrounding each conductor is also assumed to be homogeneous and independent of frequency.
polyimide: $\epsilon_r=3.4$
\end{enumerate}
As an example, the cable specification for the 20AWG cable, variant 14 from \cite{3901/019}
TP\_AWG\_20\_ESCC\_3901019\_V14.cable\_spec:
\begin{verbatim}
#MOD_cable_lib_dir
LIBRARY_OF_CABLE_MODELS
Twisted_pair
2 # number of conductors
4 # number of parameters
4.370E-04 # parameter 1: inner conductor radius
1.520E-03 # parameter 2: inner conductor separation
7.400E-04 # parameter 3: inner dielectric radius
4.762E+07 # parameter 4: conductivity
1 # number of frequency dependent parameters
# Dielectric relative permittivity model follows
1.0 # w normalisation constant
0 # a order, a coefficients follow below:
3.400E+00
0 # b order, b coefficients follow below:
1.0
\end{verbatim}
\clearpage