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  1. #1
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    Phase diagram of s11 positive and always >0 deg

    hi
    please , when i simulate patch antenna , i find s11 for desirable frequency (fr) <-10dB (good adaptation) , but i find phase diagram of s11 positive and always >0 deg!
    what that means please (physically) and is there an error §?

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    Re: phase of s11 parameter

    Can you post an S11 plot (on a Smith Chart with some frequency markers)?

    phase of S11 always >0 means that your antenna appears to be (somewhat) inductive over the simulated frequency range. This can be a combination of certain transmission line length and non-optimum match.



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    Re: phase of s11 parameter

    yes thanks

    http://images.elektroda.net/58_1346759078.jpg

    and look please , i have good adaptation in s11 magnitude coefficient (s11<-10dB)!



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    Re: Phase diagram of s11 positive and always >0 deg

    Nothing wrong with this!

    If you change the match a bit, the S11 graph (on Smith chart) may encircle the center of the graph, and then you will see negative phase also.

    If you would add a quarter wave transmission line between the actual feedpoint and the source, the S11 curve will be in the negative half of the Smith Chart. You may know that adding a 90 degrees long transmission line (50 Ohms, assuming 50 Ohms reference impedance), will rotate the curve on the Smith chart over -180 degrees.



  5. #5
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    Re: Phase diagram of s11 positive and always >0 deg

    De-embedding the port along the length of the transmission line will also counteract it's effect - essentially, giving you the phase response at the edge of the patch antenna.



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