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  1. #1
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    Using a 0db Attn as termination

    Hello Microwave Forum,

    I am trying to incorporate a RF power detector in my circuit at C-band to understand if a discontinious cable or a rusty connector exists between my antenna and PA.

    I have a circulator after my PA to protect the circuit for reflections. Circulator's unused port is terminated with 50ohm to dissipate the power reflected from mismatches(normally). I want to show a 50 ohm termination to that port while simultaneously sampling the power in-line with a detector.

    ---Can I use a 0 db attenuator to show circulator's 3rd port 50 ohm termination while sampling the reflected power with a RF power detector. I tried drawing a schematic where normal lines are forward power and dashed lines are reflected power in case of a discontinuity, is this logical?

    Click image for larger version. 

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    Kind Regards,

    ktr

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  2. #2
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    Re: Using a 0db Attn as termination

    What do you mean by 0dB attenuator? In your drawing, is that "0dB" device a ferrite isolator or why does it provide isolation?



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    Re: Using a 0db Attn as termination

    Hello Dr. Volker,

    Quote Originally Posted by volker@muehlhaus View Post
    What do you mean by 0dB attenuator? In your drawing, is that "0dB" device a ferrite isolator or why does it provide isolation?
    Thanks for replying. That's the part I'm struggling to figure out, if reasonable. If not properly terminated circulator does not work; hence I thought maybe a 0-db attenuator will provide the 50-ohm match to circulator. In MaximIntegrated site there is a similar topology given; picture below.

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    This is the datasheet of the 0-db attenuator I mentioned.

    https://www.mouser.com.tr/datasheet/...or-1154282.pdf



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  4. #4
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    Re: Using a 0db Attn as termination

    Quote Originally Posted by ktr View Post
    I thought maybe a 0-db attenuator will provide the 50-ohm match to circulator.
    From your datasheet, that is a series of SMD attentuators. Different values including 0 dB can be used for post-layout level adjustment.

    The attenuator will improve matching by 2*A dB, where A is the attenuator value in dB. The 0dB will behave like any other thru line, it doesn't improve return loss.
    Last edited by volker@muehlhaus; 19th June 2019 at 14:39.



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