One example discloses a vibration sensor, comprising: an RF receiver circuit configured to receive an RF input signal； an RF signal characterization circuit configured to measure an attribute of the RF input signal over a set time-period； wherein the attribute of the RF input signal varies based on a physical motion between the vibration sensor and an RF source transmitting the RF input signal； and a vibration profiling circuit configured to map the attribute of the RF input signal to a vibration level.
