[HN Gopher] Where Did RFID Come From? [video]
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Where Did RFID Come From? [video]
Author : ksec
Score : 44 points
Date : 2024-07-07 13:12 UTC (2 days ago)
(HTM) web link (www.youtube.com)
(TXT) w3m dump (www.youtube.com)
| dzhiurgis wrote:
| So if I understand correctly some types of RFID can be tracked
| from satellite. Makes sense if you got something like SAR sats to
| be used for imaging.
| GaryNumanVevo wrote:
| Active RFID tags do exist, but they're basically just a
| wireless transponder with a battery. Satellite tracking
| probably exists but it would need a fair amount of power and a
| non-noisy RF environment.
| akira2501 wrote:
| > fair amount of power
|
| My favorite thing about GPS is all satellites broadcast on
| the same carrier frequencies and the received signal at the
| surface of the earth is several dB below the noise floor.
| Which you can do with complicated signal encoding involving
| known values at the receiver and a really slow overall
| bitrate on top of a much faster carrier.
| eru wrote:
| There's more to it: they increased the overall accuracy
| (and I guess implicitly the bitrate?) over time much
| further than was originally intended, by more clever
| electronics and math on the receiver.
| RF_Savage wrote:
| For passive tags the power densities and antenna sizes in
| orbit would be genuinely use.
|
| For active tags it's a transponder like any other satellite
| tracker.
| GaryNumanVevo wrote:
| Jon is one of my favorite historians / writers in the
| semiconductor space! His videos are great but they're just recaps
| of his weekly substack (which is also excellent)
| asianometry.substack.com
| michaelt wrote:
| I've worked with EPC RFID tags professionally - those are the
| tags that can be read at a distance of a few meters, and that can
| (sometimes) be brought for a few cents. It's an interesting
| technology, but it's never going to replace barcodes en masse, in
| the retail space.
|
| One major issue is the read rate - if you're getting a 99% read
| rate your RFID setup is uncommonly good, but in retail failing to
| charge for 1% of items isn't sustainable.
|
| When RFID tags are used for marathon timing, they'll often give
| each runner two tags, and set up two or three reader portals at
| the start/finish line, because using a single tag and a single
| reader portal just doesn't give a good enough read rate.
|
| The technology is also exceptionally difficult to debug - the
| signal from the reader is orders of magnitude more powerful than
| the reply from the tags, and they both transmit at the same time.
| So even if you've got professional wireless engineers with $50k
| spectrum analysers, they'll be able to tell you the reader is
| operating, but won't be able to measure the strength of the tag's
| responses.
|
| There are of course an endless stream of things to fiddle with -
| different reader antennas, multiple reader antennas, different
| tag antenna shapes, different tag types for sticking to different
| materials, tags that work better in certain orientations, tags
| that are designed for use on metal, tags that are designed for
| use on metal but with a 2mm foam pad for backing, and so on. Of
| course the famous two cent RFID tags are the very most basic
| ones.
|
| And you can get crossover between reader portals - the readers
| are of course very sensitive to the returned signal, so if you
| have two portals side by side the left portal can power a tag
| passing through it, and the response can be strong enough for
| left and right portals to both detect it. You can imagine how
| this would be a problem for supermarket checkouts.
|
| Not to mention the fact a two cent RFID tag costs too much to be
| put onto a 30 cent can of beans, which might only have a three
| cent profit margin.
|
| The real benefit of RFID tags is in being able to track high-
| value/high-markup items like razor blades throughout the entire
| supply chain. When the razor blade factory ships out X packs in Y
| boxes on Z pallets, you can count every packet out of the factory
| and into the distribution hub, then out of the distribution hub
| and so on, ensuring none go missing. Read failures are less of a
| problem here, because if a pallet shows up as missing an item you
| can stop it and scan it again. The tags are also used in things
| like hotel towels which are constantly being sent between the
| hotel and the laundry provider, to make sure shipments contain
| the number of towels they're supposed to contain.
| RF_Savage wrote:
| With some care, you can see the tag replies with a 10eur rtl-
| sdr, but the rest if the software stack does not exist for
| free. CISC will sell you a license to rent the software, but
| you need to provide your own rtl-sdr stick.
|
| Voyantic (now Impinj) has their own software that used an
| Airspy sdr, but it was end-of-lifed after Impinj bought them.
|
| And then for just cimparing tag performance, there is Voyantics
| Tagformance tester, but that's for comparing tag performance,
| not debugging something.
|
| But yeah, really annoying to see anything on a nornal swept
| spectrum analyzer.
| calmbonsai wrote:
| I recall the example used in many white papers being the
| scanning of a pallet of soda cans inside of an open truck or
| shipping container. All of the multi-path interference would've
| made it one of the hardest environments I can image for getting
| reliable reads.
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