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Fast RFID

Reinaldo Gurewitsch
Prodigy 30 points

Dear Sirs

We need to implement a project where RFID tags are placed on the ground, one or more per each traffic lane, and readers mounted on passing vehicles.


The data we need to read on these tags, is just a 6 digits number.


We would like to know what will be the best Reader/Tag selection,  to be able to read this info when travelling at high speed (Hopefully: 60 meters/second), as well as all limitations to be considered (Reading distance, etc).

Best regards

  • 0
    TI__Guru* 91206 points

    Reinaldo - 

    are you 100% sure on the speed? (this equates to 216km/h or 134.2mph) usually - in my experiences around the world with toll areas, they like for you to slow down a bit and there are only a few places in the world where you can do that kind of speed in the first place (the Autobahn, for example, but even they make you slow down in spots) - only other places i think of are race tracks...

    anyway - technically - lets break it down - for example lets say you were using Low Frequency (LF, 134.2kHz) or High Frequency (HF, 13.56MHz) RFID technology and the antenna was 1 meter wide. this means the tag will be in the field (it will be read on the outside edges, too) so for simple feasibility purposes here - the tag would then be in the field (lets say it (the field) is 1.2m wide) for ~20mSec. This is enough time for HF tag read (you need ~ 6mSec for inventory read and response), but not LF (you need 20mSec minimum just to charge up the tag with this technology) 

    So then its a question of reading distance after that. What are you looking at there? maybe its pretty far away - so then if its greater than 2m...then you might need to go to considering an electric field technology like EPC Gen2 and a linear antenna to get most distance or a completely active electric field technology with a wake receiver if you need to conserve battery life on the tag.

     

     

     

  • 0 in reply to Josh Wyatt
    Prodigy 30 points

    Hi Josh

    Thanks for your answer.

    The speed will vary (0-200 km/h).

    Since the reader will be mounted under the car, pointing to the ground, we need to use a small antenna.

    The reading rate shall be as fast as possible to be able to read the tag as many times as possible.

    An important point is to avoid reading from nearby lanes, each one of them will have its own code, so the antenna shal cover a diameter of no more than 1-1.5 meters at a distance to the ground of aprox. 40 centimeters where the tag will be.

    Do you think we need HF or UHF to accomplish that. (Obviously the least expensive will be a better choice, since we'll need a high number of readers).

    Regards

  • 0 in reply to Reinaldo Gurewitsch
    TI__Guru* 91206 points

    most likely HF will work out for you, but will require some custom antenna work - at 40cm distance, for reliable reading, you could start with Feig Reader solution (they sell 1W output MR101, for example) and use full size ISO15693 HF tag from TI. http://www.ti.com/product/ri-i02-112a-03 

    For example, with the Feig 300mm x 300mm and their reader, you can get 48cm read distance, which allows you some guardband....a longer but same width antenna should give you the passover area to cover the speed requirement. 

  • 0 in reply to Josh Wyatt
    Prodigy 30 points

    Thank you very much. I'll give it a try.