Can a the s-parameters of a rg58 coaxial transmission line be calculated. If yes, what are they?
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\$\begingroup\$ s-parameters are an arbitrary choice when it comes to measurement. It doesn't necessarily have to be s-parameters. It could be ABCD-parameters if you wanted to. There are different ways to model a transmission line. \$\endgroup\$– user103380Commented Jan 30, 2019 at 17:26
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\$\begingroup\$ What problem are you trying to solve by having the s-parameters of your cable? Do you have the actual physical cable and a network analyzer available so you can just measure them? \$\endgroup\$– The PhotonCommented Jan 30, 2019 at 17:27
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\$\begingroup\$ Yes, the S-parameters of RG-58 can be calculated. This might help you to get more details. \$\endgroup\$– YogeshCommented Jan 30, 2019 at 17:33
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\$\begingroup\$ @ThePhoton I'm trying to simulate how a RG58 coax cable interferes with a circuit when used as a testing probe to measure the voltage. To simulate the coax cable I wanted to use a two-port model where I can specify the s parameters. \$\endgroup\$– elFreakCommented Jan 30, 2019 at 21:45
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The insertion loss and phase delay (\$S_{21}\$ and \$S_{12}\$) can be roughly calculated from the specifications of the cable.
You can use
$$S_{21} = S_{12} \approx Ae^{-j\theta}$$
where \$A\$ is calculated from the insertion loss (i.e. 10 dB insertion loss would give \$A = \sqrt{0.1}\$), and \$\theta\$ is the electrical length of the cable.
The return loss and phase of the reflection (\$S_{11}\$ and \$S_{22}\$) will depend more on the quality of the connectors you use than on the cable itself.
answered Jan 30, 2019 at 22:54
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\$\begingroup\$ Does the 100 pf/meter matter? \$\endgroup\$ Commented Jan 31, 2019 at 3:58
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\$\begingroup\$ @analogsystemsrf, I don't see how it directly affects finding the S-parameters. It does relate to the velocity factor, but hopefully you'll get the velocity factor as a separate spec and not have to work it out from L and C per unit length. \$\endgroup\$ Commented Jan 31, 2019 at 6:00