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    single shunt stub (short)

    hello
    is S11 of single stub matching network must equal S22? and is it necessary for both to satisfied matching ?

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    Re: single shunt stub (short)

    It depends what your matching to. Do you have the same characteristic impedance on both sides?



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    Re: single shunt stub (short)

    Quote Originally Posted by loletta View Post
    hello
    is S11 of single stub matching network must equal S22? and is it necessary for both to satisfied matching ?
    answer for both question is yes. is not must be but it will be!! its because since single stub is unilateral. bilateral devices (transistors and etc) will have S11 not equal to S22. but unilateral S11 = S22.



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    Re: single shunt stub (short)

    I need to match 50 ohm transmission line to ZL=60-80j



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    Re: single shunt stub (short)

    I design single stub to match 50 ohm transmission line to zl=60-80j in HFSS as shown in the following figure but the result show that S11 is matched but S22 isn't.



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    Re: single shunt stub (short)

    Hi

    Just a quick note.
    If your scale is in dB, then something is wrong. Because you actually have gain in this passive matching structure...
    So maybe check your HFSS setup.



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    Re: single shunt stub (short)

    I change sweep type from fast to discrete but no change in the result.
    I try to design the following circuit from pozar's book.



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    Re: single shunt stub (short)

    Ok.
    I can only tell you that it is a passive structure(circuit) and you can not have S-parameters greater than zero dB.
    So there must definetly be something with your simulation setup or drawing in HFSS.



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    Re: single shunt stub (short)

    Quote Originally Posted by tyassin View Post
    I can only tell you that it is a passive structure(circuit) and you can not have S-parameters greater than zero dB.
    So there must definetly be something with your simulation setup or drawing in HFSS.
    Unless the correct reference impedances aren't being used. Can you plot Zo(1) and Zo(2) as a function of frequency?



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    Re: single shunt stub (short)

    this is the magnitude of Z



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    Re: single shunt stub (short)

    Hmmm....you have a constant impedance over the whole frequency range. That can not be possible for a frequency dependent network.



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    Re: single shunt stub (short)

    Quote Originally Posted by tyassin View Post
    Hmmm....you have a constant impedance over the whole frequency range. That can not be possible for a frequency dependent network.
    According to the image, a lumped port is being used -- thats one problem. It's very likely the impedances are not matched. Use waveports and see what values they give you -- I'd suspect they will be different than the ones you have entered.



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  13. #13
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    Re: single shunt stub (short)

    please can you check the design
    note (fc=2.4GHz)



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