System and method for calibrating a vehicular traffic surveillance Doppler radar

• US 7,057,550 B1
• Filed: 02/16/2005
• Issued: 06/06/2006
• Est. Priority Date: 02/16/2005
• Status: Active Grant

• Current Assignee: Applied Concepts Incorporated (Emerson Electric Company)
• Original Assignee: Applied Concepts Incorporated (Emerson Electric Company)
• Inventors: Aker, John L.
• Primary Examiner(s): Gregory, Bernarr E.
• Application Number:
  US11/059,474
• Time in Patent Office: 475 Days
• Field of Search: 342 89-116, 342/118, 342127-147, 342165-175, 342192-197, 342/27, 342/28, 342 70- 72, 342 82- 88
• US Class Current: 342/174
• CPC Class Codes: G01S 13/348 using square or rectangular modulation, e.g. diplex radar for ranging over short distances
• CPC Class Codes: G01S 13/584 adapted for simultaneous range and velocity measurements
• CPC Class Codes: G01S 13/92 for velocity measurement
• CPC Class Codes: G01S 13/931 of land vehicles
• CPC Class Codes: G01S 7/4021 of receivers

Abstract

A system and method for calibrating a vehicular traffic surveillance Doppler radar are disclosed. In one embodiment, a modulation circuit portion generates double-modulated FM signals. An antenna circuit portion transmits the double-modulated FM signals to a target and receives reflected double-modulated FM signals therefrom. A calibration circuit portion responds to the reflected double-modulated FM signals by sending a calibration signal to the modulation circuit. The calibration signal is indicative of a relationship between a first range measurement derived from phase angle measurements associated with the reflected double-modulated FM signals and a second range measurement derived from speed and time measurements associated with the reflected double-modulated FM signals.

Claims

1. A system for calibrating a vehicular traffic surveillance Doppler radar, the system comprising:

a modulation circuit portion for generating modulated FM signals;

an antenna circuit portion for transmitting the modulated FM signals to a target and receiving reflected modulated FM signals therefrom; and

a calibration circuit portion, responsive to the reflected modulated FM signals, for determining a calibration signal and sending the calibration signal to the modulation circuit portion, where the calibration circuit portion determines the calibration signal by comparing a first range measurement derived from phase angle measurements associated with the reflected modulated FM signals and a second range measurement derived from speed and time measurements associated with the reflected modulated FM signals.

2. The system as recited in claim 1, wherein the modulated FM signals form a portion of a continuous FM signal.

3. The system as recited in claim 1, wherein the modulated FM signals comprise double-modulated FM signals.

4. The system as recited in claim 1, wherein the modulation circuit portion comprises an oscillator selected from the group consisting of dielectric resonator oscillators and Gunn diode oscillators.

5. The system as recited in claim 1, wherein the antenna circuit portion comprises a duplexer coupled to an antenna, the duplexer guiding the modulated FM signals from the modulation circuit portion to the antenna and guiding the reflected modulated FM signals from the antenna to the calibration circuit portion.

6. The system as recited in claim 1, wherein the calibration circuit portion comprises:

a quadrature circuit portion coupled to the antenna circuit portion and the modulation circuit portion, the quadrature circuit portion for performing a quadrature demodulation using the reflected modulated FM signals; and

a processing circuit portion, responsive to the quadrature demodulation, for performing a fast Fourier transform analysis to determine the first range measurement and the second range measurement.

7. The system as recited in claim 1, wherein the calibration signal adjusts applied voltages of an oscillator frequency versus voltage characteristic associated with the modulation circuit portion.

8. The system as recited in claim 7, wherein the oscillator frequency versus voltage characteristic comprises a non-linear, temperature dependent relationship between the applied voltages and the modulated FM signals.

9. The system as recited in claim 1, wherein the calibration signal corrects an over modulation condition associated with the modulation circuit.

10. The system as recited in claim 1, wherein the calibration signal corrects an under modulation condition associated with the modulation circuit.

11. The system as recited in claim 1, wherein the calibration signal maintains modulation conditions associated with the modulation circuit.

12. A method for calibrating a vehicular traffic surveillance Doppler radar, method system comprising:

transmitting modulated FM signals from the Doppler radar to a target;

receiving reflected modulated FM signals at the Doppler radar from the target;

determining a first range measurement of the target based upon phase angle measurements associated with the reflected modulated FM signals;

determining a second range measurement of the target based upon speed and time measurements associated with the reflected modulated FM signals; and

calibrating the Doppler radar by comparing the first and second range measurements.

13. The method as recited in claim 12, wherein transmitting the modulated FM signals further comprises transmitting a continuous FM signal including the modulated FM signals.

14. The method as recited in claim 12, wherein transmitting the modulated FM signals further comprises transmitting double-modulated FM signals from the Doppler radar to the target.

15. The method as recited in claim 12, wherein transmitting the modulated FM signals further comprises transmitting modulated FM signals from the Doppler radar to a target in response to an expiration of a predetermined period of time.

16. The method as recited in claim 12, further comprising correcting an over modulation condition associated with the Doppler radar.

17. The method as recited in claim 12, further comprising correcting an under modulation condition associated with the Doppler radar.

18. The method as recited in claim 12, further comprising maintaining modulation conditions associated with the Doppler radar.

19. A system for calibrating a vehicular traffic surveillance Doppler radar, method system comprising:

means for transmitting modulated FM signals from the Doppler radar to a target and receiving reflected modulated FM signals therefrom;

means for determining a first range measurement of the target based upon phase angle measurements associated with the reflected modulated FM signals;

means for determining a second range measurement of the target based upon speed and time measurements associated with the reflected modulated FM signals; and

means for calibrating the Doppler radar by comparing the first and second range measurements.

20. The system as recited in claim 19, wherein the means for transmitting the modulated FM signals further comprises means for transmitting a continuous FM signal including the modulated FM signals.

21. The system as recited in claim 19, wherein the means for transmitting modulated FM signals further comprises means for transmitting double-modulated FM signals from the Doppler radar to the target.

22. The system as recited in claim 19, wherein the means for transmitting the modulated FM signals further comprises means for transmitting modulated FM signals from the Doppler radar to a target in response to an expiration of a predetermined period of time.

23. The system as recited in claim 19, further comprising means for correcting an over modulation condition associated with the Doppler radar.

24. The system as recited in claim 19, further comprising means for correcting an under modulation condition associated with the Doppler radar.

25. The system as recited in claim 19, further comprising means for maintaining modulation conditions associated with the Doppler radar.

26. A system for vehicular traffic surveillance, the system comprising:

a Doppler radar that transmits modulated FM signals and receives reflected modulated FM signals; and

a target vehicle that generates the reflected modulated FM signals in response to the modulated FM signals,

wherein the Doppler radar self-calibrates by utilizing a calibration circuit portion to compare a first range measurement derived from phase angle measurements associated with the reflected modulated FM signals and a second range measurement derived from speed and time measurements associated with the reflected modulated FM signals.

27. The system as recited in claim 26, further comprising a police vehicle onto which the Doppler radar is mounted.

28. The system as recited in claim 26, wherein the Doppler radar self-calibrates to correct an over modulation condition in a frequency versus voltage characteristic associated with the Doppler radar.

29. The system as recited in claim 26, wherein the Doppler radar self-calibrates to correct an under modulation condition in a frequency versus voltage characteristic associated with the Doppler radar.

30. The system as recited in claim 26, wherein the Doppler radar self-calibrates and maintains modulation conditions associated with a frequency versus voltage characteristic of the Doppler radar.

31. The system as recited in claim 26, wherein the modulated FM signals form a portion of a continuous FM signal.

32. The system as recited in claim 26, wherein the modulated FM signals comprise double-modulated FM signals.