Hi,

I am working on a project, whare I explore different fault detection methods for coaxial cables. For that purpose I created two Ansys simulations of coaxial cables, whare one is the control and one is damaged. I want to know if my Ansys HFSS simulation results are correct. I simulated the impedance of a RG59 coaxial cable in Ansys HFSS in the TDR mode. My cable is 30mm long and all the other parameters are the same as specified in the RG59 datasheet.

RG59 coaxial cable


Impedance of RG59 coaxial cable


Damaged RG59 coaxial cable


Impedance of damaged RG59 coaxial cable
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The damaged section of the cable is present only in the dielectric. I was expecting the undamaged coaxial cable to have a strait line as the impedance graph but I was surprised when it was vary wavey.

I appreciate all the help I will get.
Have a grate day!
Domen

 

The vertical scales of the two plots are not the same.
With the undamaged cable, the signal ranges from 73.1 to 73.9, that is ±0.5%

 

The vertical scales of the two plots are not the same.
With the undamaged cable, the signal ranges from 73.1 to 73.9, that is ±0.5%

Thank you, yes my scale was wrong!

 

With wildly different scales it is difficult to understand the effect of the damage. With the undamaged cable it mostly looks about the same. So how about a processor and a really fast A/D converter. probably six bits would be adequate. It needs to be REAL FAST because that whole dip is 0.02 Pico-seconds wide. That is quite narrow.

As an alternative, how about using the total transmission delay time to determine the frequency of an oscillator. Using a section of transmission line as the resonant element of an oscillator has been done. Then counting the frequency is a well understood process, and correlating that to distance is a well defined process.