Using Smith Chart to determine impedance on other side of LC filter

Discussion in 'Wireless & RF Design' started by Telegraph, Mar 12, 2018.

  1. Telegraph

    Thread Starter New Member

    Mar 12, 2018
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    Using an antenna analyzer to look at the impedance of a low band antenna. Problem is there is a strong AM station that overloads the analyzer. If a filter (band stop or high pass) is placed between the antenna and analyzer all I see is the impedance out of the filter. The value measured varies with different loads on the other side. I thought I might be able to use a Smith Chart to take the impedance as measured by the analyzer and calculate back through the filter to determine what is on the antenna side. I made the filter so I know what the values are for the capacitors and inductors.

    Using both manual calculations on the Smith Chart and on-line Smith Chart tools I am unable to get this to work. I am using a load to simulate the antenna in the lab. My calculations do not come anywhere near the simulated load.

    Anyone have any thoughts on this approach?
     
  2. danadak

    Well-Known Member

    Mar 10, 2018
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  3. Telegraph

    Thread Starter New Member

    Mar 12, 2018
    2
    0
    Yes, the S-parameters should work. I think I found my problem. Basically the problem was between the Smith Chart and my chair. :) The model I made was not entirely correct. Adding to that I made a few mistakes on the Smith Chart.

    Thanks for the input.

    Mike
     
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