Ever wonder what is inside a toll way RFID tag? The windshield on one of our cars had to be replaced the other day and we removed the toll way RFID tag before taking the car to the shop so I could peek inside. I doctored the picture here so the registration number is not shown.
Here is the back side of the tag after it was removed from the windshield. You can see a layer of copper covered by a plastic adhesive. There was a noticeable bump on the front side of the tag so used an X-Acto knife to cut near the bump. I found that the front side was covered in a film of plastic that could be peeled away.
The picture to the right shows the RFID circuit exposed after peeling away the top layer of plastic. The tan-colored area shows the copper backing on the opposite side of the tag. White areas are not covered with copper on the back side. There is a small IC in the center area of the tag. The large copper area and the shorter traces on this side form the antenna. The IC is the only other component in the tag.
Using a flat bed scanner as described in a previous article, I did a high resolution scan of the chip as you can see in the last picture here. The chip is marked with two strings “4085″ and “201F”. A Google search did not yield the details for this chip. I assume it is a custom part for TxTag.
Let us know with a comment if you have any information on this chip. I do not want to do any hacking to get free toll access. I am just interested in the technology.