A method is provided for determining a number of revolutions per minute (RPM) of a rotating object. The method includes transmitting interrogation signals at a regular period from a fixed antenna positioned adjacent to the rotating object. The method also includes transmitting echo signals from a sensor antenna positioned on the rotating object, in response to the interrogation signals. The method also includes counting a number of echo signals detected by the fixed antenna, during one revolution of the object. The method also includes determining the RPM of the rotating object based on the number of response signals and the regular period of the signals. A system is also provided for determining the number of revolutions per minute (RPM) of the rotating object.