Material property comparison based on TDR and delta L

[yefj]

Hello ,As you can see in the plot bellow I have made several TDR of different materials on one plot.
I need to deside which is the best material to use.
Also I know that based on (S21_10inch-S21_5inch)/L I find the loss per inch.
Two questions:
1.after I find the loss per inch how do I find the tan_delta and e_r of the material?
2.looking at this TDR comparison how can I see the best performing material?
Thanks.

 

[Baluncore]

From the top right corner of your plot, how do you know the impedance of materials A-E? Were they calculated or were they measured using some instrument? You should be able to either, identify the Er was used for their computation, or extract Er from the TDR measurement.

In your case, with a very-long line, the TDR impedance will appear to be Zo = 100Ω. All plots will over longer times, decay exponentially to Zo. In effect, the impedance measurement is being attenuated with the attenuation of the signal. Try to extrapolate lines, (between zero and infinite resistance), with exponential decay towards Zo on the right.

Notice with TDR, that inductance appears to be infinite resistance, while capacitance appears to be zero resistance. I do not see how a TDR plot can give you Tan-d, as the TDR plots the magnitude of the reflected vector, without resolving the separate Z=R+jX components.

TDR is a broad-band plot of impedance against time, not against frequency or phase. To measure Tan-d, (which increases with frequency), you will need to make a two port VNA measurement at a single specified frequency.

 

[yefj]

Hello Baluncore,I know that as the los in bigger then tdr slope is larger.
all material TDR is plotted together and loss per inch plot is attached.
what colclution can we get from these plots ?
Thanks.

 

[Baluncore]

what colclution can we get from these plots ?

Without context, I can tell nothing.

From the top right corner of your plot, how do you know the impedance of materials A-E? Were they calculated or were they measured using some instrument?