Research, development and trades concerning the powerful Proxmark3 device.
Remember; sharing is caring. Bring something back to the community.
"Learn the tools of the trade the hard way." +Fravia
You are not logged in.
Time changes and with it the technology
Proxmark3 @ discord
Users of this forum, please be aware that information stored on this site is not private.
I'm looking at the schema and trying to wrap my head around the hardware design.
Can anyone explain what each of the components are doing in the RF front end?
I'm particularly interested in the section between C14 and C16 (both inclusive). I have very little experience with electronic design, but am guessing that it might be a low pass filter to remove the 13.56MHz carrier. Is that right?
Also, I presume that IC9 and IC10 are there to drive the carrier and signal when in reader mode and to provide a load on the external antenna when simulating a tag. I'm I understanding that correctly?
Offline
Ok, to partially answer my own question (using doc/proxmark3_schema.pdf as reference):
D2, C15 and R15 appear to be an envelope detector, which is what would be removing the 13.56MHz carrier. Still not sure as to how the values were determined, other than that larger values of R*C mean longer charge / discharge times. As such, it makes sense that R15*C15 is smaller than R11*C11 as the latter would be trying to detect the envelope on a lower (ie. slower) carrier frequency.
D10 appears to be a shunt diode used for over voltage protection. It is rated at 47V and if I understand things correctly, it means that if more than around 47V is present, it will divert the excess to ground. I'm guessing that IC14, IC6 and IC5 can handle voltages above that and that this diode is only really to define a max voltage for AMPL_HI.
R41 and R42 is a voltage divider. It means that AMPL_HI has 1/10 (or is it 1/11) the voltage of the signal entering R16. This would suggest that the peak voltage at AMPL_HI is around 4.7V.
Not sure what C14 and C16 (and C35 for that matter) are doing, but am guessing they help clean up the signal a little by acting as a set of filters. Don't know in what way, what cut off frequencies, etc. though.
Don't have an idea of what D3 is for at all at the moment. Maybe to counteract D2, which on its own might act as a half wave rectifier? But then why is there no equivalent on the LF side?
Offline