Modulation circuit for a vehicular traffic surveillance Doppler radar system

• US 7,049,999 B1
• Filed: 02/16/2005
• Issued: 05/23/2006
• 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:
  US11/059,199
• Time in Patent Office: 461 Days
• Field of Search: 342/27, 342/28, 342104-122, 342128-145, 342/175, 342194-198, 342/200, 342/201, 342/147
• US Class Current: 342/114
• 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

Abstract

A modulation circuit for a traffic surveillance Doppler radar system is disclosed. In one embodiment, the modulation circuit is utilized in a vehicular traffic surveillance Doppler radar system that processes a reflected double-modulated FM signal to determine a target range based upon a phase angle signal differential associated with the target. The modulation circuit may include a digital-to-analog (D/A) converter/voltage regulator/oscillator arrangement or a D/A converter/varactor device/oscillator arrangement. The modulation circuit generates a double-modulated FM signal based upon a frequency versus voltage characteristic associated with the oscillator.

Claims

1. A vehicular traffic surveillance Doppler radar system comprising:

a modulation circuit portion for generating a double-modulated FM signal by utilizing an oscillator frequency versus voltage characteristic;

an antenna circuit portion coupled to the modulation circuit, the antenna circuit portion operable to transmit the double-modulated FM signal to a target and receive a reflected double-modulated FM signal;

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 double-modulated FM signal; and

a processing circuit portion, responsive to the quadrature demodulation, for calculating a target range based upon a phase angle signal differential associated with the target.

2. The vehicular traffic surveillance Doppler radar system as recited in claim 1, wherein the modulation circuit portion comprises:

a digital-to-analog convertor for converting a plurality of digital inputs to a convertor voltage output;

a voltage regulator, responsive to the convertor voltage output, operating in combination with the digital-to-analog convertor to generate first and second oscillator input voltages; and

an oscillator, responsive to the first and second oscillator input voltages, for generating the double-modulated FM signal.

3. The vehicular traffic surveillance Doppler radar system as recited in claim 1, wherein the modulation circuit portion comprises:

a digital-to-analog convertor for converting a plurality of digital inputs to a convertor voltage output; and

a varactor device positioned within a cavity of an oscillator, the varactor device, responsive to the convertor voltage output, for tuning the double-modulated FM signal.

4. The vehicular traffic surveillance Doppler radar system as recited in claim 1, wherein the antenna circuit portion comprises a duplexer coupled to an antenna, the duplexer guiding the double-modulated FM signal from the modulation circuit portion to the antenna and guiding the reflected double-modulated FM signal from the antenna to the quadrature circuit portion.

5. The vehicular traffic surveillance Doppler radar system as recited in claim 1, wherein the processing circuit portion comprises a digital signal processor for performing fast Fourier transform analysis on data associated with the quadrature demodulated, reflected double-modulated FM signals.

6. The vehicular traffic surveillance Doppler radar system as recited in claim 1, wherein the processing circuit portion determines a target speed based upon a frequency signal differential associated with the target.

7. The vehicular traffic surveillance Doppler radar system as recited in claim 1, wherein the processing circuit portion performs a fast Fourier transform that results in an approaching target spectrum and a receding target spectrum to determine a target direction.

8. A modulation circuit for a vehicular traffic surveillance Doppler radar system, the modulation circuit comprising:

a digital-to-analog convertor for converting a plurality of digital inputs to a convertor voltage output;

a voltage regulator, responsive to the convertor voltage output, operating in combination with the digital-to-analog convertor to generate first and second oscillator input voltages; and

an oscillator, responsive to the first and second oscillator input voltages, for generating a double-modulated FM signal based upon a frequency versus voltage characteristic associated with the oscillator.

9. The modulation circuit as recited in claim 8, wherein the digital-to-analog convertor comprises a multi-bit, multi-wire serial interface digital-to-analog convertor.

10. The modulation circuit as recited in claim 8, wherein the voltage regulator comprises a positive voltage regulator having an input-output differential of approximately 5 V.

11. The modulation circuit as recited in claim 8, wherein the oscillator comprises a Gunn diode oscillator.

12. The modulation circuit as recited in claim 8, wherein the frequency versus voltage characteristic defines a non-linear, temperature dependent relationship between the first and second oscillator input voltages and the double-modulated FM signal.

13. A modulation circuit for a vehicular traffic surveillance Doppler radar system, the modulation circuit comprising:

a digital-to-analog convertor for converting a plurality of digital inputs to a convertor voltage output; and

a varactor device positioned within a cavity of an oscillator, the varactor device, responsive to the convertor voltage output, for tuning a double-modulated FM signal generated by the oscillator.

14. The modulation circuit as recited in claim 13, wherein the digital-to-analog convertor comprises an multi-bit, multi-wire serial interface digital-to-analog convertor.

15. The modulation circuit as recited in claim 13, wherein the varactor device comprises a two-terminal diode operating in the microwave-range.

16. The modulation circuit as recited in claim 13, wherein the oscillator is selected from the group consisting of dielectric resonator oscillators and Gunn diode oscillators.

17. The modulation circuit as recited in claim 13, wherein the frequency versus voltage characteristic comprises a non-linear, temperature dependent relationship between the first and second oscillator input voltages and the double-modulated FM signal.

18. A method for vehicular traffic target resolution comprising:

utilizing a frequency versus voltage characteristic associated with an oscillator of a radar system to generate a double-modulated FM signal;

transmitting the double-modulated FM signal from the radar system to a target;

receiving a reflected double-modulated FM signal at the radar system;

performing a quadrature demodulation using the reflected double-modulated FM signal; and

responsive to the quadrature demodulation, determining a target range based upon a phase angle signal differential associated with the target.

19. The method as recited in claim 18, wherein the frequency versus voltage characteristic comprises a non-linear, temperature dependent relationship between voltages supplied to the oscillator and the double-modulated FM signal.

20. The method as recited in claim 18, wherein performing the quadrature demodulation further comprises mixing the reflected double-modulated FM signal with a local oscillator signal generated by the oscillator.

21. The method as recited in claim 20, wherein mixing the reflected double-modulated FM signal further comprises shifting, prior to the mixing, the double-modulated FM signal by an integer multiple of 90 degrees relative to the local oscillator signal.

22. The method as recited in claim 20, wherein mixing the reflected double-modulated FM signal further comprises shifting, prior to the mixing, the local oscillator signal by an integer multiple of 90 degrees.

23. The method as recited in claim 18, wherein determining a target range further comprises performing a fast Fourier transform on data associated with the reflected double-modulated FM signals.

24. The method as recited in claim 18, further comprising determining a target speed based upon a frequency signal differential associated with the target.

25. The method as recited in claim 18, further comprising performing a fast Fourier transform that results in an approaching target spectrum and a receding target spectrum to determine a target direction.