2.4GHz radio signal through small gaps

[paul_harris77]

For an engineering project I am trying to place a 2.4GHz RFID tag inside a resin casting of a large seaside pebble. However since the resin is less dense than a real pebble, I need to add some mass of metal (since is is much denser) to the resin before it sets. It is crucial for the casting to have the same moment of inertia as a real pebble and so as uniform a distribution of metal inside the casting as possible. The only way I can think of doing this is to use a large amount of iron filings added to the resin mixture before it sets. This means the gaps between the filings will be much smaller than the wavelength of the 2.4GHz signal.

Will this significantly attenuate the signal into / out of the RFID antenna inside the resin pebble, or are the filings so thin that it would make as little as no difference?

Any help would be greatly appreciated.

Many thanks

Paul

 

[Vanadium 50]

Why dork around with metals? Why not use a non-metal that's dense: lead carbonate has a density of close to 7.

 

[paul_harris77]

Thanks for the reply.

I need a material that is non-toxic in case the resin were to break open. Whilst I am sure a pebble breaking here and there and exposing a tiny bit of lead carbonate would pose little if any environmental damage/toxicity, there would still likely be a restriction on its use in a product like this.

 

[Vanadium 50]

Fine. Use flint glass then.

Seriously, I think you want to attack this as a materials science problem, not as a EE problem.

 

[f95toli]

Iron/copper fillings in resin (or expoxy) is used to make very efficient microwave filters and absorbers...I would use something else if I were you.