In this work, we present a method for simultaneous ranging of multiple transponders. The method was implemented on a software defined radio (SDR) and investigated by measurement. The ranging method investigated here is based on a frequency-modulated continuous-wave (FMCW) radar. The signal, modulated via backscattering at the transponder, is used by the interrogator to distinguish and separate the signal of one transponder from clutter as well as from the backscattered signals of other transponders. We demonstrate in a series of measurements that simultaneous ranging of multiple transponders is possible with this novel technique. Using a bandwidth of 10MHz at 5. 8GHz a mean absolute error of 5. 9cm was achieved. The influence of clutter and the signal of other transponders is removed from the signal of the investigated transponder.