Do rare earth magnets interfere with RF?

[Jakevsnake]

Im a bit of a physics newb so bare with me. I am designing a product that uses rare Earth magnets as a mounting solution for radar detectors and wanted to know if these magnets would somehow interfere with the performance of the radar detector? The magnets will not be mounted to the detector itself, but will be an inch or so away from the chassis of the detector. I asked this on my radar detector forums and got some mixed views on if this would cause problems with the detector. If it matters these detectors scan frequencies primarily in the 24-36Ghz. I appreciate any insight you may share.

 

[jedishrfu]

No effect unless the magnet is directly blocking the signal just like a chunk of metal blocks signals.

 

[lekh2003]

No problem whatsoever. It would interfere if it was a changing magnetic field (like a spinning magnet) or if the magnet literally blocks the radar like jedishfru said.

Don't worry about it. If you want to be a little more sure, maybe you can test it ().

 

[davenn]

Im a bit of a physics newb so bare with me.

and if you don't mind, we will leave our clothes on and instead will bear with you

 

[Jakevsnake]

Thanks for the input. I do appreciate you keeping your clothes on :)

 

[berkeman]

Well, there is an issue that hasn't been addressed yet...

If the magnetic field can reach any magnetics on your PCBA (inductors, chokes, transformers, etc.), that can cause saturation issues, which changes the effective values of those inductances. You need to keep the stray magnetic field from the magnets well away from your PCBA's components.

It's common for RF modules to have electric field shielding (little metal can shields over the component areas), but I've not seen any that incorporate B-field shielding...

 

[Jakevsnake]

I guess the question now is how close is close with regards to the PCBA? I know my cell phone gets mounted in my car with a strong magnetic mount and there are no issues. The magnets would stand about a 1/2inch from the outside of the chassis. I may have to consider some design changes if this proves to be an issue. Will have to look into shielding the magnets use in the mount so the magnetic field doesn't affect the PCBA.

 

[berkeman]

What do the magnets look like? As long as the final magnetic path is closed (like with horseshoe magnets stuck to a metal plate), then there will not be much stray flux. OTOH, if the magnets are open before the unit is stuck to something, and a couple units can pass close to each other, there may be an issue with the strong open magnetic field from one unit's magnets possibly causing residual problems with the magnetics in the other unit. The ferrites used in RF inductors, etc., tend to have a pretty low value of Br, so that may not be an issue...

https://www.electronics-tutorials.ws/electromagnetism/mag19.gif
https://www.electronics-tutorials.ws/electromagnetism/mag19.gif