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IFA layout design for CC2541

ray chen1
Prodigy 90 points
Other Parts Discussed in Thread: CC2541, CC2540

Hi :

I am designing CC2541and plan to layout few days later.  After taking a closer look and do a comparison on the 2.4GHz IFA antenna design on various EVBs, I see some IFA layout not well followed the swra117d. I don't know if that is because of EVB or it is really also ok for end product design.  Below are my questions:

1. In CC2541 KeyFob, the antenna ground connected to PCB ground plane on top layer, but in swra117d, it strongly recommend to use a "via" connecting to GND.  Both ways are good  or only the latter one is recommended for end product design ?  Using a "via " is important or just better to follow or doesn't matter ?

  

                  Fig 1.                                                                                    Fig 2.

2.  In Fig 2 (CC2540 USB ), the antenna gnd follows the swra117d, but why the trace between the antenna gnd and system gnd needs to be a " winding" trace ? can't it be a straight line ?  any special reason to design so ?

3. The width of the layout trace of the feeding point / gnd point is also different between fig 1, fig 2 and swra117d , which one is better for me to follow ? use thinner trace width before going to antenna (like Fig 2) or keep  the same trace width as antenna (Fig1) ?

Looking forward to your professional advice.

Ray

  • 0
    Prodigy 90 points

    attache the file in case you can't see fig1 and fig 2 in previouse port.

  • 0
    TI__Genius 12545 points

    Ray

    1. On closer inspection you will see that there are vias on the top ground plane near the antenna feed point for the CC2541 keyfob. This is just not visible due to the copper pour on the top layer. But it is strongly recommended that you put vias close to the ground connection point. This allows for a strong ground connection of the antenna to the ground plane.

    2. In the CC2540 USB dongle, there was no copper pour for ground on the top layer near the antenna ground, hence we had to directly connect the ground to a via connecting to the ground planes on the layers below. Generally if you have copper pour around the antenna ground point, it is preferred.

    3. Please folow the antenna layout shown in figure1.

  • 0 in reply to Chatto
    Prodigy 90 points

    I got your point. Thanks for your input.