RF transformer impedance matching problem for fet mixer

Discussion in 'Wireless & RF Design' started by zachnikolic, Jun 12, 2018.

  1. zachnikolic

    Thread Starter New Member

    Feb 7, 2018
    8
    0
    Hello,

    I am designing a dual gate mosfet mixer to drive a 50 ohm load. Without the transformer the mixer has a gain of 3, but when I add the transformer and a 50 ohm load the gain is dropped to .5. Also with the transformer the signal is centered around 0 volts, which negates my biasing. I believe I used the correct formula when designing the transformer, Np/Ns = sqrt(Zp/Zs) and I got a turns ratio of 11:2. L values calculated using FT 37-43 core. Attached is the ltspice asc file as well as the mosfet asy and sub files. Also attached are pics of the schematic and simulation results taken across the 50 ohm load.

    Thanks
     
  2. Janis59

    Active Member

    Aug 21, 2017
    579
    92
    Hmmm, but where is the question??
     
  3. bertus

    Administrator

    Apr 5, 2008
    18,587
    3,600
  4. zachnikolic

    Thread Starter New Member

    Feb 7, 2018
    8
    0
    Sorry,
    my question is why does my gain drop at the output of the transformer?
     
  5. Bordodynov

    Well-Known Member

    May 20, 2015
    1,918
    578
    See
    2018-06-13_11-32-04.png
     
  6. Bordodynov

    Well-Known Member

    May 20, 2015
    1,918
    578
    See Without a transformer
    2018-06-13_11-51-48.png
     
Loading...