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RF Trace Width Issue

Hi,

after calculating the trace width for 50Ohm impedance line, the width is 0.30 mm.

  1. There is no problem at traces but on QFN pins  which have a limited spacing, could RF traces have a neck near to SMT pins without affecting too much to RF line impedance? So, RF traces fit in a proper way to avoid any DRC error.
  2. In case there's no option to reduce the line width in this case, if I maintain the current line width, will the nearest pins (VDD) to RF ones affect to RF signal integrity?
  3. Does any rule of thumb to route the RF trace on the PCB? 
  4. What is the common clearance between the RF trace and ground plate?

Regards.

  • Hi Alv,

    1) The length of these are so short that the impedance does not matter
    2) Ok to reduce width
    3) Follow the reference design
    4) Use a impedance calculator, like TX-line to calculate. Typically you can make co-planar waveguides with ground with 50 ohm impedance with 0.15 - 0.2 mm clearance to surrounding ground plance.

    Cheers,
    Fredrik