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  1. #1
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    RF Switch with diode

    Hello
    I design a switch with pin diode but I couldn’t recognize about impedance matching stay correct or not.
    Here is my design
    Click image for larger version. 

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    excuse me for bad shape
    When large signal come (60 dbm 18 GHz) it(diode) should be off but in small signal ( -20 dbm ) should be on and nothing receive to antenna neither return loss to rfin and all should go to gnd.
    When it is off I think that it is like an stub and change my impedance is it correct?
    And when it is on should I connect directly to gnd?
    is it correct I place R1 before diode because I saw only place after diode in rf applications?
    And I don’t consider about duty cycle in my design.
    I gave my reverse voltage according to AN3022 mycom It says “For p-i-n diodes with I-region thickness less
    than approximately 1 mil (25 μM), an external dc reverse bias equal to the peak RF voltage is required, regardless
    of duty cycle. This reverse bias requirement is relaxed, however, for thicker p-i-n diodes and low RF duty cycles
    (D) so that 10 mil (250 μM) diode requires at most 35 V reverse bias to keep within the conditionally safe reverse
    bias region under any duty cycle.”

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  2. #2
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    Re: RF Switch with diode

    1000W@18GHz ??? Is it a joke ??



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  3. #3
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    Re: RF Switch with diode

    no i want only use reverse vo;tage from paper

    my design is in 10GHz and 400W



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    Re: RF Switch with diode

    I believe you want a high-Q shunt C at the PIN diode
    cathode, to signal ground. Otherwise the circuit as
    drawn will "kill" the PIN diode C(fwdBias) inductively.

    For the kind of wattage you are talking, you need to
    figure out the AC current and the "on" diode power
    dissipation vs those datasheet ratings. If you figure
    that 1W Pdiss is a threshold-of-concern then 400WRMS
    to 50 ohms, 8A RMS (give or take), would say you
    need a PIN diode Rs of 15mOhm.



  5. #5
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    Re: RF Switch with diode

    Quote Originally Posted by Dummyeng View Post
    no i want only use reverse vo;tage from paper
    my design is in 10GHz and 400W
    To my knowledge, Solid State PIN Diodes are not robust to carry those Power Levels..



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  6. #6
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    Re: RF Switch with diode

    Quote Originally Posted by BigBoss View Post
    To my knowledge, Solid State PIN Diodes are not robust to carry those Power Levels..
    As i said when high power comes, it is off and all of it (power) go t o antenna.



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