US Patent 11238670 Determining the passing time of a moving transponder

In a method for determining the passing time of a moving transponder passing a detection antenna of a base station, a sequence of first signals are exchanged between a first transponder coil and the detection antenna, and a sequence of second signals are exchanged between a second transponder coil and the detection coil. The first and/or second signals are associated with time instances indicating the time when the first and/or second signals are exchanged between the transponder and the base station. The passing time of said transponder is determined on the basis of the signal strengths of the first and second signals and the time instances.