QUESTION

Question

We did not design the board in question and do not have schematics but I was hoping to find out more about the applications this part is used in. We have 120MHz noise all over are board and cannot isolate it.

Thanks

Dave Anderson

Answer 1

Hi Dave,

The part in question is a low-profile, surface mount, 2.4GHz antenna. It's used in BT/ BLE, WiFi, ZigBee, and any other 2.4-2.5GHz applications.

Without knowing more about the board, I can say with some certainty that it is unlikely the antenna is causing these issues. The post below titled "How do I determine the source of RSE? I've only got basic equipment" has some good replies on how to determine sources of RSE and what equipment you'd likely need.

Thanks,

Dan

Comments

Thanks Dan

I appreciate the input.

The radio module we are using is the USRWIFI232-D2 and we just purchased a RIGOL DSA815 spectrum analyzer and when we use a near field probe we see the 120MHz on at least 1/2 of the pins coming off that module.

We put the WIFI module in the manufacturers programming board that we purchased from then and we see the 120 MHz coming of the WIFI module there also.

We could try a common mode choke or something if we could isolate it to one area.

Any thoughts?

---

Hi Dave,

This is common when integrating off the shelf modules for many products and can be tricky without the availability to redesign. At this stage, filtering with a choke, shielding, using RF absorber material, or some combination of the three are typically going to be your best approach. 

Here is a link to absorber sheets you can purchase individually to see if you can dampen the noise at the source. The idea is to start with a larger piece at the source of the noise and start trimming to the smallest necessary size as the material isn't cheap, even at volume.  

https://www.mouser.com/ProductDetail/3M-Electronic-Specialty/AB6005S?qs=sGAEpiMZZMtQwYqzsFSgXAx3nfe5pIZUpYQPo1N656A%3D

Thanks,

Dan