Doppler Shift using BladeRF in GNURadio

[SameerIrfan]

Hi, I'm working on BladeRF xA9 and trying to send and receive a signal using an antenna. I am sending the signal from one BladeRF on a metal foil and receiving it in real time with another when the signal gets reflected. Now I am planning to oscillate the metal foil and find its doppler shift. I have tried to make a frequency modulated wave using a VCO but don't know how I can demodulate it when it is received. If someone could help me out it would mean a lot. Please if someone could explain how can I find the Doppler Shift of the target using the BladeRF it would be of great help. Also, please send if you have any frequency modulation and demodulation file in GNURadio it would also help a lot. Thanks