Traffic surveillance radar using ranging for accurate target identification

• US 6,798,374 B1
• Filed: 11/05/2002
• Issued: 09/28/2004
• Est. Priority Date: 11/05/2002
• Status: Expired due to Fees

• Current Assignee: Decatur Electronics, Incorporated
• Original Assignee: Decatur Electronics, Incorporated
• Inventors: Smith, Kimble Jon
• Primary Examiner(s): GREGORY, BERNARR E
• Application Number:
  US10/288,010
• Time in Patent Office: 693 Days
• Field of Search: 342/27, 342/28, 342/59, 342/70, 342/71, 342/72, 342/104-118, 342/128-133, 342/145, 342/146, 342/147, 342/175, 342/192-197
• US Class Current: 342/109
• CPC Class Codes: G01S 13/536 using transmission of continuous unmodulated waves, amplitude-, frequency-, or phase-modulated waves
• CPC Class Codes: G01S 13/583 using transmission of continuous unmodulated waves, amplitude-, frequency-, or phase-modulated waves and based upon the Doppler effect resulting from movement of targets
• CPC Class Codes: G01S 13/87 Combinations of radar systems, e.g. primary radar and secondary radar
• CPC Class Codes: G01S 13/92 for velocity measurement

Abstract

Disclosed is a Doppler shifted radar apparatus for correct target identification with respect to surveillance of moving vehicles. More particularly, an improved radar detection system using two or more continuously transmitted frequencies is used. The multiple frequencies are directed toward target vehicles whereby the phase difference of the two or more reflected Doppler signals is calculated and subsequently used to accurately determine a target range, thereby displaying the closest vehicle and closest vehicle speed. Vehicle speed is determined with use of the standard Doppler frequency shift. The next closest and/or next faster vehicle speed can also be easily determined.

Claims

1. An apparatus for remotely determining the range of a first target, the apparatus comprising:

a first oscillator generating a first frequency RF signal;

a second oscillator generating a second frequency RF signal;

a combiner receiving the first and the second frequency RF signals and outputting a continuous, complex transmitted signal;

a target reflected signal receiver which receives a Doppler, continuous complex signal and separates a Doppler first frequency signal and a Doppler second frequency signal; and

a signal processor which receives the Doppler first frequency signal and the Doppler second frequency signal and computes a phase shift between the Doppler first and second signals, thereby determining a range of the target.

2. The apparatus of claim 1, wherein the signal processor further computes a speed of the first target.

3. The apparatus of claim 2, wherein the signal processor further computes a range and a speed of the first target, and a range and a speed of a plurality of targets.

4. The apparatus of claim 3, wherein the signal processor controls a display to show a closest target'"'"'s speed chosen from the first and the plurality of target'"'"'s speeds.

5. The apparatus of claim 4, wherein the signal processor controls the display to show a next closer target'"'"'s speed.

6. The apparatus of claim 3, wherein the signal processor controls the display to show a fastest target'"'"'s speed.

7. The apparatus of claim 4, wherein the signal processor controls the display to show a fastest target'"'"'s speed.

8. The apparatus of claim 5, wherein the signal processor controls the display to show a next faster target'"'"'s speed.

9. The apparatus of claim 1, wherein the first oscillator further comprises a fixed frequency oscillator, and the second oscillator further comprises a variable frequency oscillator.

10. The apparatus of claim 9 further comprising a feedback loop and controller to maintain a fixed frequency offset between the first and second oscillator by varying the frequency of the second oscillator.

11. An apparatus for remotely determining the speed and range of a plurality of targets, the apparatus comprising:

a first oscillator generating a first frequency RF signal;

a second oscillator generating a second frequency RF signal;

a combiner receiving the first and the second frequency RF signals and outputting a continuous, complex transmitted signal;

a target reflected signal receiver which receives a Doppler, continuous complex signal and separates a Doppler first frequency signal and a Doppler second frequency signal for each of the plurality of targets;

a signal processor which receives the Doppler first frequency signal and the Doppler second frequency signal for each of the plurality of targets and computes a phase shift between the Doppler first and second signals for each of the plurality of targets, thereby determining a range of each target; and

said signal processor also determining a speed for each target using either the Doppler first or second signal for each target.

12. The apparatus of claim 11, wherein the signal processor controls a display to show a closest target'"'"'s speed chosen from the plurality of target'"'"'s speeds.

13. The apparatus of claim 12, wherein the signal processor controls the display to show a next closer target'"'"'s speed.

14. The apparatus of claim 11, wherein the signal processor controls the display to show a fastest target'"'"'s speed.

15. The apparatus of claim 12, wherein the signal processor controls the display to show a fastest target'"'"'s speed.

16. The apparatus of claim 14, wherein the signal processor controls the display to show a next faster target'"'"'s speed.

17. The apparatus of claim 15, wherein the signal processor controls the display to show the next faster target'"'"'s speed.

18. The apparatus of claim 11, wherein the first oscillator further comprises a fixed frequency oscillator, and the second oscillator further comprises a variable frequency oscillator.

19. The apparatus of claim 18 further comprising a feedback loop and controller to maintain a fixed frequency offset between the first and second oscillator by varying the frequency of the second oscillator.

20. A method of remotely determining the speed and range of a plurality of moving targets, the method comprising the steps of:

a) transmitting a continuous complex RF signal consisting of a combination of a first frequency signal and a second frequency signal;

b) receiving a target reflected signal from a plurality of moving targets;

c) converting the target reflected signal to extract a first frequency Doppler signal and a second frequency Doppler signal;

d) measuring a phase shift between the first frequency Doppler signal and the second frequency Doppler signal;

e) separating each target'"'"'s first and second Doppler signal; and

f) computing for each target its range and speed.

21. The method of claim 20 including the steps of:

a) selecting a target based on its range or on its speed from the plurality of targets; and

b) displaying the selected target'"'"'s range or speed.

22. The method of claim 20 further including the steps of:

a) converting the target'"'"'s reflected first frequency Doppler signal from an analog signal to a first digital Doppler signal;

b) converting the target'"'"'s reflected second frequency Doppler signal from an analog signal to a second digital Doppler signal;

c) providing a clock generation circuitry for time multiplexing both the first digital Doppler signal and the second digital Doppler signal;

d) providing a signal processor to perform a fast fourier transform to determine the spectral content to separate a plurality of target data from the first digital Doppler and the second digital Doppler signal;

e) providing a signal processor to compute a phase difference between the first digital Doppler signal and the second digital Doppler signal;

f) using the computed phase difference to compute a target range for each of the plurality of targets;

g) using the frequency of the first digital Doppler signal or the second digital Doppler signal to compute a target speed for each of the plurality of targets; and

h) storing each computed target speed and range for further display.

23. The method of claim 22, wherein the provided signal processor compares the frequencies of first digital Doppler signal and the second digital Doppler signal, and disregards the computed target'"'"'s speed and range data if the difference in compared frequencies is greater than a set magnitude.

24. An apparatus for remotely determining the range of a first target, the apparatus comprising:

a circuit generating a first frequency RF signal and generating a second frequency RF signal and generating a combined complex first and second frequency RF signal transmitted signal;

a target reflected signal receiver which receives a Doppler, continuous complex signal and separates a Doppler first frequency signal and a Doppler second frequency signal; and

a signal processor which receives the Doppler first frequency signal and the Doppler second frequency signal and computes a phase shift between the Doppler first and second signals, thereby determining a range of the first target.

25. The apparatus of claim 24, wherein the signal processor further computes a speed of the first target.

26. The apparatus of claim 25, wherein the signal processor further computes a range and a speed of the first target, and a range and a speed of a plurality of targets.

27. The apparatus of claim 26, wherein the signal processor controls a display to show a closest target'"'"'s speed chosen from the first and the plurality of target'"'"'s speeds.

28. The apparatus of claim 27, wherein the signal processor controls the display to show, a next closer target'"'"'s speed.

29. The apparatus of claim 28, wherein the signal processor controls the display to show a next faster target'"'"'s speed.

30. The apparatus of claim 27, wherein the signal processor controls the display to show a fastest target'"'"'s speed.

31. The apparatus of claim 26, wherein the signal processor controls the display to show a fastest target'"'"'s speed.

32. An apparatus for remotely determining the speed and range of a plurality of targets, the apparatus comprising:

a circuit generating a first frequency RF signal and a second frequency RF signal and combining the first and the second frequency RF signals and outputting a continuous, complex transmitted signal;

a target reflected signal receiver which receives a Doppler, continuous complex signal and separates a Doppler first frequency signal and a Doppler second frequency signal for each of the plurality of targets;

a signal processor which receives the Doppler first frequency signal and the Doppler second frequency signal for each of the plurality of targets and computes a phase shift between the Doppler first and second signals for each of the plurality of targets, thereby determining a range of each target; and

said signal processor also determining a speed for each target using either the Doppler first or second signal for each target.

33. The apparatus of claim 32, wherein the signal processor controls a display to show a closest target'"'"'s speed chosen from the plurality of target'"'"'s speeds.

34. The apparatus of claim 33, wherein the signal processor controls the display to show a next closer target'"'"'s speed.

35. The apparatus of claim 33, wherein the signal processor controls the display to show a fastest target'"'"'s speed.

36. The apparatus of claim 35, wherein the signal processor controls the display to show the next faster target'"'"'s speed.

37. The apparatus of claim 32, wherein the signal processor controls the display to show a fastest target'"'"'s speed.

38. The apparatus of claim 37, wherein the signal processor controls the display to show a next faster target'"'"'s speed.