+ Post New Thread
Results 1 to 3 of 3
  1. #1
    Member level 2
    Points: 1,378, Level: 8

    Join Date
    Oct 2012
    Posts
    45
    Helped
    0 / 0
    Points
    1,378
    Level
    8

    RF PCB - Design Guidline

    Hi,

    I already made a couple of PCBs operating at lower frequencies. Currently I'm planing to realize a project operating in the sub - GHz range. I have seen a lot of pictures of realized RF projects. Most times the PCBs does not have a ground plane at the top layer. Is there a reason for that, beside the PCBs most times look like the are etched at home . I found the following document http://www.ti.com/lit/an/swra367a/swra367a.pdf, on page 5 a top layer GND plane is recommended.

    I know I should avoid a GND plane below a signal path due to due stray capacitances, as for low frequencies. Are there any other recommentations?


    BR

    •   AltAdvertisment

        
       

  2. #2
    Advanced Member level 4
    Points: 6,520, Level: 19

    Join Date
    Jun 2012
    Location
    Edmonton, Canada
    Posts
    1,009
    Helped
    292 / 292
    Points
    6,520
    Level
    19

    Re: RF PCB - Design Guidline

    Microwave engineering is its own field of study. Various PCB features can act as resonators and/or antennas, the choice of dielectric itself can have a large impact on performance, and characteristic impedance becomes a critical concept.

    So long as you can keep all of your trace lengths electrically short (smaller than one fifth of a wavelength), you should be OK with basic rules of thumb. Otherwise... you'll need to to quite a bit of study first!

    The no ground plane on top is one type of waveguide, with a ground plane on top it becomes another, and removing the bottom ground plane gives yet another type. You'll need to know what these are -- check out the terminology for microstripline, coplanar waveguide, and conductor-backed coplanar waveguide.



    •   AltAdvertisment

        
       

  3. #3
    Full Member level 6
    Points: 2,777, Level: 12
    SLK001's Avatar
    Join Date
    Aug 2015
    Location
    Coral Springs, Florida
    Posts
    384
    Helped
    137 / 137
    Points
    2,777
    Level
    12

    Re: RF PCB - Design Guidline

    I've laid out many an RF PCB for both military and commercial applications and each and every one of them had a ground plane on the top layer. I use Co-Panar Waveguide for the PCB topology.



--[[ ]]--