Wikipedia:Reference desk/Archives/Miscellaneous/2016 September 13

= September 13 =

Vehicle RFID
The pictures show a vehicle RFID system installed for toll collection in Norway. Can anyone identify the internal components of the active tag carried by every vehicle?  1. 3.6V 1.6Ah Lithium battery 2. ? 3. ? 4. ? 5. ? 6. ? 7. ?  AllBestFaith (talk) 16:32, 13 September 2016 (UTC)


 * There's a bot that can be told to rotate photos but I don't know which one. Or it could be edited on your computer and a new version uploaded. † Dismas †|(talk) 17:21, 13 September 2016 (UTC)
 * The image rotation is correct in my camera and computer but somehow turned when I uploaded it to Wikipedia. AllBestFaith (talk) 17:42, 13 September 2016 (UTC)


 * 4 and 7 are microchips. Or did you need something more specific? 6 could be as well but it's a bit hard to tell with the image at its current resolution.  † Dismas †|(talk) 17:24, 13 September 2016 (UTC)


 * 3 appears to be a spacer or a gasket or a washer of some sort. -- Jayron 32 18:28, 13 September 2016 (UTC)
 * Just a guess, but I suspect that 5 is the antenna. --Stephan Schulz (talk) 18:34, 13 September 2016 (UTC)
 * When assembled, metal disc 3 faces the two long slots visible as a "V" under the NORBIT legend in the bottom center image. I think these are quarter-wavelength cavity resonators coupled to the Microstrip antenna 5. AllBestFaith (talk) 19:48, 13 September 2016 (UTC)
 * Since it's possible to read the part number on 7 (1PT1039), we can tell it's a piezoelectric transducer (spec sheet here ), apparently for generating sounds. The printing on the other chips is too small to read in this photo. CodeTalker (talk) 23:57, 13 September 2016 (UTC)
 * Wikipedia has an article about the AutoPASS system in which this RFID or DSRC transponder is used. There is no mention of an ability to make a beep noise that could surprise a driver. I speculate that it could be there for production testing i.e. when each unit is programmed with the vehicle identity, and/or is a means to alert someone to unpaid tolls or stolen vehicle. AllBestFaith (talk) 11:32, 14 September 2016 (UTC)
 * According to the catalogue: "The integrated buzzer can be activated from the roadside during a DSRC transaction. Buzzer tones can be customized to suite various needs." Smurrayinchester 13:05, 14 September 2016 (UTC)


 * Component 2 is presumably a piece of power electronics - maybe a Crystal oscillator for converting the DC current produced by the battery into pulses for electronics/driving an antenna. But as CodeTalker says, we need to know what's printed on the chips to know what they really are. All packages look basically the same. I think the precise antenna type is an aperture-coupled patch antenna - the microstrip lines on the front feed power to/from the slots visible on the back, and these in turn couple to the metal disc. So (in transmit mode) the signal flows up the printed microstrip lines, then into the slots, then into the disc, which radiates them (I can't find an illustrations of this exact antenna, but this one is quite similar, as is this one). I think from the arrangement of the slots and the way that one arm of the microstrip is longer than the other means that this tag is circularly polarized (which is good because it ensures that the orientation of the RFID tag doesn't matter too much), and the weird ring looks like a Wilkinson power divider, which splits equally power between the slots while ensuring that power from one slot can't flow to the other. Smurrayinchester 08:13, 14 September 2016 (UTC)
 * At operating frequency 5.8 GHz a quarter wavelength is 1.3 cm in air. Here are the markings on the microchips:

    2. 4-pin marked C2KNR3L 4. 32-pin marked NORBIT NBX60 SUD4868 1402 6. 8-pin marked C23R
 * AllBestFaith (talk) 11:32, 14 September 2016 (UTC)
 * The one marked NORBIT will presumably be a custom ASIC, so maybe there's not much to be said about that one. Smurrayinchester 13:05, 14 September 2016 (UTC)