Author Topic: 7" capacitive touch radiated emissions  (Read 2101 times)

briching

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7" capacitive touch radiated emissions
« on: January 25, 2016, 02:32:48 PM »
We have reached the first round of radiated emissions testing for our product using a Newhaven 7" capacitive touch module driven by an NXP LPC4357.  Unfortunately the offending radiated frequencies point to the LCD, and we're wondering if anyone has any resources they could point us to that would help us pass.  Any tips and tricks as far as what can be done with the ribbon cable or change the design would be appreciated as well.

So far, we've tried ferrite beads, copper foil tape on the ribbon cable, as well as a number of other mods to our boards (filtering, decoupling, etc).  The best effect seems to be achieved by affixing copper foil tape to the back of the LCD and running it down the entire length of the ribbon cable, then inserting this through a narrow ribbon cable ferrite core. 

Is anyone else experiencing their LCD as the tall pole in their radiated emissions testing?

Regards,
Brad

Paul_B

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Re: 7" capacitive touch radiated emissions
« Reply #1 on: February 05, 2016, 08:48:56 AM »
Morning Brad,

There are virtually unlimited number of ways that you can fail a radiated emissions test, below are a few tips that should help you pass  ;)

  • Ground the TFT's bezel, copper tape comes in handy
  • Utilize flat cable Ferrite core (used for FPC/FFC cable)
  • Utilize EMI shielding foils and film
  • Board decoupling

Hope this helps, feel free to contact me if you have any questions or concerns.

 

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