Patent ID: 7119736

Claim:
Distance determination system for determining the distance from a base station (BS) to a transponder (TR), wherein the base station (BS) has an oscillating signal source (OSZ B ) for generating a signal (s tx (t)) and a transmission device (ANT B ) for radiating out the signal (s tx (t)), the transponder (TR) has a receiving device (ANT T ). for receiving the signal (e rxt (t)) from the base station (BS), an oscillator (OSZ T ) for generating a signal (s OSZ (t)) which is quasi-phase-coherent with the signal (e rxt (t)) from the base station (BS), and a transmission device (ANT T ) for radiating out the quasi-phase-coherent signal (s OSZ (t)), the oscillator (OSZ T ) excited with the received signal (S rxt (t)) into generating a quasi-phase-coherent signal (s OSZ (t)), the base station (BS) has in addition a receiving device (ANT B ) for receiving the quasi-phase-coherent signal (s OSZ (t)) from the transponder (TR) and distance determination equipment (RMIX, FLT, DEMOD) for determining the distance (dist) between the base station (BS) and the transponder (TR), and the distance determination equipment (RXMIX, FLT, DEMOD) in the base station (BS) has a mixer (RXMIX) for mixing the quasi-phase-coherent signal (s rxt (t)) received from the transponder (TR) and the instantaneous transmit signal (s tx (t)) to form a mixture signal (S mix (t)).