Given a radio transmitter (like a cell-phone or wireless computer), how can you measure the rise time remotely?
I understand that you can use an oscilloscopes to measure it on components at hand, but apparently, telcoms analyze the cell-phones' rise time to obtain a radio fingerprint of each device (and being able to tell if a device is a clone of another).
Best Answer
The following blog page Transmitter Fingerprinting contains some information. I couldn't find the particular patent mentioned although I was searching by the name Phil Farrell , possibly it was lodged under a company name or too old to be available in on-line patent databases. Certainly the claims made all sound perfectly plausible and relate to changes in the carrier frequency as the transmitter stabilizes. In that article it quotes the following as being from the former Motron website who used to sell the product:
There is also an open source project called XMIT_ID and while somewhat dated being written for DOS it does have source code available. I also found an article about a Windows application called SherlockXP written by WA9BVS although couldn't find a download location for it so I'm not sure if it's still available.
Those techniques are mainly aimed at transmitters with simple modulation schemes but I imagine for digital transmitters most of it would still apply and it could be augmented with further analysis in the digital domain.