METHODS AND SYSTEMS FOR DETERMINING A RANGE RATE FOR A BACKSCATTER TRANSPONDER
First Claim
1. A method of determining a range rate of a vehicle-mounted backscatter transponder in a roadway using an automatic vehicle identification system, the system including an antenna defining a coverage area for communicating with the backscatter transponder, the range rate being a rate of change of a distance between the transponder and the antenna, the method comprising:
- transmitting, via the antenna, a continuous wave signal having a carrier frequency;
receiving a modulated reflected response signal from the transponder, wherein the modulation is at a modulation frequency;
converting the modulated reflected response signal to a downconverted signal by mixing the modulated reflected response signal with the carrier frequency;
bandpass filtering the downconverted signal to pass a bandpass filtered signal containing at least the modulation frequency;
applying a non-linear amplitude transfer function to the bandpass filtered signal to remove modulation and produce a modulation-suppressed signal;
measuring the frequency of the modulation-suppressed signal; and
determining the range rate based upon a Doppler shift corresponding to the measured frequency of the modulation-suppressed signal.
1 Assignment
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Accused Products
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.
20 Citations
17 Claims
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1. A method of determining a range rate of a vehicle-mounted backscatter transponder in a roadway using an automatic vehicle identification system, the system including an antenna defining a coverage area for communicating with the backscatter transponder, the range rate being a rate of change of a distance between the transponder and the antenna, the method comprising:
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transmitting, via the antenna, a continuous wave signal having a carrier frequency; receiving a modulated reflected response signal from the transponder, wherein the modulation is at a modulation frequency; converting the modulated reflected response signal to a downconverted signal by mixing the modulated reflected response signal with the carrier frequency; bandpass filtering the downconverted signal to pass a bandpass filtered signal containing at least the modulation frequency; applying a non-linear amplitude transfer function to the bandpass filtered signal to remove modulation and produce a modulation-suppressed signal; measuring the frequency of the modulation-suppressed signal; and determining the range rate based upon a Doppler shift corresponding to the measured frequency of the modulation-suppressed signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 17)
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9. A reader for determining a range rate of a vehicle-mounted backscatter transponder in a roadway, the reader comprising:
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a transmitter to generate a continuous wave signal having a carrier frequency; an antenna to transmit the continuous wave signal and to receive a modulated reflected response signal from the transponder, wherein the modulation is at a modulation frequency, and wherein the range rate is a rate of change of a distance between the transponder and the antenna; a mixer to mix the modulated reflected response signal with the carrier frequency to produce a downconverted signal; a bandpass filter to filter the downconverted signal to pass a bandpass filtered signal containing at least the modulation frequency; a non-linear amplitude transfer function to produce a modulation-suppressed signal when the function is applied to the bandpass filtered signal to remove modulation; and a frequency measurer to measure the frequency of the modulation-suppressed signal and to determine the range rate from the measured frequency. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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Specification