Abstract: A method for determining a lateral position of a vehicle passing a road and carrying a transponder uses at least two antennas mounted at different lateral positions and connected to a processor and comprises: triggering the transponder and recording signals from responses of the transponder by the processor, each signal being received via one of the antennas and recorded as i) a time of receipt at said one antenna and ii) the lateral position of said one antenna; generating by the processor a regression curve fitting all recorded signals; and determining by the processor the lateral position of the vehicle from the generated regression curve. An apparatus implementing said method is also disclosed.

Abstract: Methods of estimating vehicle location in a roadway using an automatic vehicle identification system are described. The methods involve receiving a set of response signals from a vehicle-mounted transponder at points in time and determining a range rate of the transponder relative to the antenna at each point in time; identifying a minima in the magnitude of the range rate; estimating a first position of the transponder at a first time corresponding to the occurrence of the minima; estimating a velocity of the vehicle based upon one or more of the determined range rates; and estimating a second position of the transponder based upon the first position and the velocity.

Abstract: Methods for determining a range rate of a backscatter transponder and readers implementing the methods are described. The reader transmits a continuous wave signal and receives a modulated reflected response signal from the transponder, mixes the modulated reflected response signal with the carrier frequency to produce a downconverted signal, bandpass filters the downconverted signal to pass a bandpass filtered signal containing at least the modulation frequency, applies a non-linear amplitude transfer function to produce a modulation-suppressed signal, and measures the frequency of the modulation-suppressed signal and determines the range rate from the measured frequency.

Abstract: Methods of estimating vehicle location in a roadway using an automatic vehicle identification system are described. The methods involve receiving a set of response signals from a vehicle-mounted transponder at points in time and determining a range rate of the transponder relative to the antenna at each point in time; identifying a minima in the magnitude of the range rate; estimating a first position of the transponder at a first time corresponding to the occurrence of the minima; estimating a velocity of the vehicle based upon one or more of the determined range rates; and estimating a second position of the transponder based upon the first position and the velocity.

Abstract: Methods for determining a range rate of a backscatter transponder and readers implementing the methods are described. The reader transmits a continuous wave signal and receives a modulated reflected response signal from the transponder, mixes the modulated reflected response signal with the carrier frequency to produce a downconverted signal, bandpass filters the downconverted signal to pass a bandpass filtered signal containing at least the modulation frequency, applies a non-linear amplitude transfer function to produce a modulation-suppressed signal, and measures the frequency of the modulation-suppressed signal and determines the range rate from the measured frequency.