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CC2538: CC2538

Kanchan Debnath
Prodigy 250 points

Part Number: CC2538
Other Parts Discussed in Thread: CC2592

I   have designed a custom Board with CC2538+CC2592,  I am using the Same BOM as in the reference Design, except for the fact that my design is 2 Layer 1.6 mm thickness board.. The Range I am getting is too low. The Indoor range I am getting i too low around  6-7 mtrs.  I am attaching herewith the screen shot of my PCB. It would be great if any one can help me out 

PCB_Design_Screenshot.docx

Do we need to add a PI network both in front of the PCB Antenna and the External Antenna Jack  for Impedance matching 

  • 0
    TI__Mastermind 36415 points

    Kanchan,

    Changing the design of the reference design from 4 to 2 layer is a more complicated task than it sounds. The CC2592 is sensitive layer thickness because it is very sensitive to the impedance of its ground connection. A 4 layer board with a much smaller distance between the top layer and the ground plane will create a smaller inductance (impedance) than a 2 layer board because the distance is higher.

    If recommend performing measurements on your hardware, you need to confirm the RF signal strength (it should be 20dBm ish) and then on a spectrum analyzer it should be clean. (power amplifiers can sometimes start to oscillate)

    Regards,
    /TA

  • 0 in reply to TA12012
    Prodigy 250 points

    Hi  

    Thank you  for your response. I will check those parameter and get back to you.  As you mentioned CC2592 is very sensitive to board thickness, bat can it be so horrible as in my case. Its hardly 6-7 m. Also I tried to keep he RF tracks as 50 Ohm for my PCB thickness. I used the AVAGO -AppCAD for impedance calculation, since mine is a coplanar wave guide type,  the calculation came out to be.  

    1. Track width  30 mil for the Antenna feed  and 6 mil  space on either side

      Basic of calculation (   Board Thickness - 1.6mm, Er- 4.6,  copper track thickness  on either side - .035mm,  Distance between layer - 1.52 mm) 

     

     But I tried to co-relate the output  of other tools available on Internet, its all the more confusing, all seem to vary a lot.  I will request you to review my PCB layout ( kept almost same as much as possible)  help me improve. 

    1602.PCB_Design_Screenshot.docx

  • 0 in reply to Kanchan Debnath
    TI__Mastermind 36415 points

    Kanchan,

    Yes, if the PA is oscillating, what happens is that PA will generate lots of RF energy at some frequency (random and determined by the layout). This RF energy will mix with your wanted signal and create lots of spurs at many frequencies. This will effectively saturate the PA completely and the overall gain of your wanted signal will decrease significantly.

    Regards,
    /TA

  • 0 in reply to TA12012
    Prodigy 250 points

    Hi  

    I t would be  helpful  if you can  have a look on my PCB and suggest things I can improve, I have designed this board and changed a lot  from my  previous board. And is hoping to get better result.  I  am holding the PCB fabrication as I thought it would  better to get it reviewed from the experts in TI.  Your review and improvement point will give me the much needed confidence. 

    I attached the screen shot of my board RF section, I am not sure if you could open the file . If not  can resend the  same. I can even send the gerber if required. 

    Best Regards 

    kanchan