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Folded bipole antenna for CC2400 - board design.

solofrain
Prodigy 130 points
Other Parts Discussed in Thread: CC2400

I can't open CC2400EM PCB design files with my CADSTAR, so here are some questions about the board.

1. Are the nine holes (seem to be beneath CC2400) blind holes? I didn't see them in top layer. Can they be vias?

2. What is the thickness of the board? And what's the dielectric constant of the board? If my PCB manufacturer can't provide the material with the exact dielectric constant as was used for CC2400EM, should I adjust the parameters of the board and the antenna (size of the antenna, distance between the antenna and the ground plane, etc, as listed in Figure 2 of AN040)? And how? Do I treat the two tracks connected to RF_P and RF_N as 50 ohms microstrips? How about the track connected to TXRX_SWITCH?

3. I see a signel ground instead of star grounding or something else used for the whole board. Please confirm it....

Thank you.

  • 0
    TI__Expert 6825 points

    Hi,

    1. They are vias going from top layer to bottom layer.

    2. You can find some info about layer thickness in the readme.txt file. The material used is standard FR4.

    3. Not sure what you mean here, but there are ground planes rather than star grounding.

  • 0 in reply to Per H
    Prodigy 130 points

    Thank you Pelle for the reply.

    I found the data in the .txt file. Btw, what's the thickness for the coppers of the four layers?

    And for the tracks connecting RF_P & RF_N. With theres parameters:

    . FR-4 board

    . top-bottom copper distance 1mm

    . top layer copper 1.5oz (0.05mm)

    The tracks should be around 2mm wide to get 50 ohm microstrips. I use Agilent AppCAD to do the calculation. Anything wrong here?

    And for the track connecting TXRX_SWITCH, it isn't necessary to be a 50 ohm microstrip, right?

    For grounding, I mean CC2400EM use a whole ground for both analog ground and digital ground. Is that right?

  • 0 in reply to solofrain
    TI__Expert 6825 points

    The copper thickness is 0.35 um, this also stated in the readme.txt.

    The traces to the RF_P and RF_N is not 50 ohm tracks. I think the best way is to copy the design as it is including the stack-up and material. For the TXRX_SWITCH it is not nessesary to have a 50 Ohm trace. It is a whole ground for both analog and digital.

    /Pelle

  • 0 in reply to Per H
    Prodigy 130 points
    Thank you.