Apparatus and method for determining a distance

An apparatus for determining a distance comprises a transmitting device, a signal transponder and a receiving device. The transmitting device is configured to provide a transmission signal at a first frequency and to transmit the transmission signal. The signal transponder is designed to receive the transmission signal to generate based on the received transmission signal a response signal having a second frequency and to send. The receiving device is configured based on a relative phase angle of the response signal to determine a reference signal having the second frequency the distance between the transponder signal, and the transmitting device or the receiving device.