On Wed, 10 Apr 2002, Tim May wrote: > How come? Because I am assuming the transponders are in the same > position on each bill. If you want to posit some "spatial diversity" > model, that helps, but not but a huge amount. This sounds too science > fictionish to actually deploy (transponders are not the same as > letters, and cannot be moved around on a random basis).
The RFIDs are small enough to be able to positioned randomly within the fabric of the bill, but it still doesn't help if they yell in unison (something much less problematic with ultrawideband, admittedly). Phased array is sure nice, but homing in on a cloud of weak emitters with cm spatial jitter doesn't sound viable. Doorway antennas should be able to pickup a RFID-tagged cash signature relatively easily, though, though it won't be able to pick up the ID of each individual bill in a stack, unless you're willing to stand in that (shielded) doorway for a long time. > UHF is hard to launch/receive from a small, planar antenna. UWB is > easier to launch from a small (< cm) antenna, but is usually too > directional. UWB packs considerable punch in very short pulses, so one obviously needs a capacitor, as the passive power is much too weak to drive it directly. Nice thing about UWB is intrinsic collision avoidance due to PRNG timing of individual pulses. > As for the proles being too cheap, too gullible to even bother to > lightly shield, sounds like evolution in action. Righto. By the time EU will be tagging banknotes (and only bigger ones) I'm very ready to crush and/or nuke the RFID tags in the microwave. > Actually, more to the point, it means that the vast infrastructure of > "remote bill readers" will, perforce, pick up the proles. True money > launderers will use shielding. (Actually, this is all oriented at > "walking around money," so the vast infrastructure will never actually > get built, as there is no interest in monitoring trivial amounts.) I could imagine airlines screening for this, though, as a big RFID splash would invite you to become a target for "random" searches, and a prospective target for confiscation. > I'm done with this thread, though.
