초록 ▼

Frequency domain processing is used to determine rapidly whether false signals are present, and to improve the accuracy of speed measurements by rejecting speed measurements that could be inaccurate due to the presence of false signals. A Doppler signal responsive to speed of a moving vehicle is gen

Frequency domain processing is used to determine rapidly whether false signals are present, and to improve the accuracy of speed measurements by rejecting speed measurements that could be inaccurate due to the presence of false signals. A Doppler signal responsive to speed of a moving vehicle is generated by a Doppler radar transceiver. A digital computer transforms the Doppler signal into a frequency domain signal such as an energy spectrum, and the speed of the moving vehicle is computed from the weighted arithmetic mean of the energy spectrum. The mean value, however, is rejected as an indication of speed if the variance of the energy spectrum from the mean exceeds a threshold, or if a differential of the spectrum with respect to frequency exceeds a threshold. The frequency domain processing of the present invention can also be used to reject certain bands of frequencies in the Doppler signal, such as bands of frequencies that differ from the mean value by more than a threshold, and the mean value can then be recomputed to provide an even better indication of the speed of the moving vehicle. Moreover, speed samples computed from successive frames of spectrum can be averaged, and the average value can be rejected as an indication of speed if the variance of the speed samples about the average value exceeds a threshold, or if the difference between successive speed samples exceeds a threshold.

대표청구항 ▼

[ What is claimed is:] [10.] A method of monitoring moving vehicles, said method comprising the steps of:(a) operating a Doppler radar transceiver to generate a Doppler signal responsive to speeds of said moving vehicles; and(b) operating a digital computer to transform said Doppler signal into a fr

[ What is claimed is:] [10.] A method of monitoring moving vehicles, said method comprising the steps of:(a) operating a Doppler radar transceiver to generate a Doppler signal responsive to speeds of said moving vehicles; and(b) operating a digital computer to transform said Doppler signal into a frequency domain signal, wherein the frequency domain signal indicates a distribution of energy of the Doppler signal as a function of frequency, and wherein the frequency domain signal has successive portions, and for each portion,(i) to compute a mean value of said each portion of said frequency domain signal,(ii) to compute a variance of said each portion of said frequency domain signal from said mean value, and(iii) to compare said variance to a threshhold, and when said variance is greater than said threshhold, to reject said each portion of said frequency domain signal as an indication of a speed of any of said vehicles, and when said variance is less than said threshhold, to compute from said each portion of said frequency domain signal a measurement of speed of one of said signals.