Is it feasible to make distance measurement to modulated scatter RFID this way?
Assuming I have one RFID wich sends data (modulated scatter)
Two RFID readers 1 and 2 placed in one enclosure, frequency difference between reader's LO is 2..3MHz
Then if
it is possible to calculate distance to RFID scatter by comparing received signal phase shift between RFID reader 1 and 2.
As a bonus, we can measure distance to moving objects, as they provide doppler shift.
But there are many movement sensors selling all over the world, and from datasheet i see it uses very simple VCO, and FMCW or FSK can be implemented by voltage on Vtune pins. Distance measurement application notes says that complex FFT of result for F1 and F2 is enough to get phase shift for each scatter.