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Calculating dimensions of a transformer on microstrip

  1. May 12, 2016 #1
    1. The problem statement, all variables and given/known data

    Using the graphs calculate lengths and widths of transformers (quarter wave) if they are realised as microstrip lines on a substrate that has Er=2 and height of 1.6mm at frequency 1.8GHz

    Z1=22.5ohm

    Z2=77.5ohm



    2. Relevant equations

    Guided wavelength = c/((Eef)^1/2)*f)

    Graphs

    http://i.imgur.com/GCVqNo1.jpg

    3. The attempt at a solution

    Using the top graph Z1 =22.5ohm for Er=2 gives an w/h ratio of 10 therefore with a height of 1.6mm width would equal 16mm

    For length it would be 1/4 of a guided wavelengh.From the bottom graph using a w/h ratio of 10 then Eeff=2

    (3*10^8) /( (4*1.8*10^9) * (2)^1/2 ) =29.5mm

    For Z2 w/h ratio for 77.5ohm = 2

    w/h of 2 from graph gives Eeff of 1.8

    Width = 1.6*2 =3.2mm

    length =(3*10^8) / (4*1.8*10^9*(1.8)^1/2 ) = 31mm
     
  2. jcsd
  3. May 12, 2016 #2

    Tom.G

    User Avatar
    Science Advisor

    Yup, I get the same answer using your Guided wavelength equation (which seems to be the one I remember.)
     
  4. May 13, 2016 #3

    Thanks for you r help Tom :)
     
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