Method for detecting a distance, a radar system and a computer program product

• US 9,310,476 B2
• Filed: 06/17/2010
• Issued: 04/12/2016
• Est. Priority Date: 06/17/2009
• Status: Active Grant

• Current Assignee: Nederlandse Organisatie Voor Toegepast-Natuurwetenschappelijk Onderzoek Tno
• Original Assignee: Nederlandse Organisatie Voor Toegepast-Natuurwetenschappelijk Onderzoek Tno
• Inventors: Janssen, Johannes Antonius Andreas, Prevo, Ren, van Heijster, Robrt Michael Evert
• Primary Examiner(s): Barker, Matthew M
• Application Number:
  US13/379,098
• Publication Number:
  US 20120169529A1
• Time in Patent Office: 2,126 Days
• Field of Search: 342/128, 342/193
• US Class Current: 1/1
• CPC Class Codes: F42C 13/045 using transmission of F.M. waves
• CPC Class Codes: G01S 13/34 using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal
• CPC Class Codes: G01S 13/345 using triangular modulation
• CPC Class Codes: G01S 13/505 using Doppler effect for determining closest range to a target or corresponding time, e.g. miss-distance indicator
• CPC Class Codes: G01S 13/84 for distance determination by phase measurement
• CPC Class Codes: G01S 13/882 for altimeters measuring height using barometric means G01C5/06
• CPC Class Codes: G01S 7/354 Extracting wanted echo-signals Doppler systems G01S13/50

Abstract

The invention relates to a method for detecting a distance between a radar system and a reflecting surface. The method comprises the steps of transmitting a frequency modulated continuous wave (FMCW) radar signal from the radar system and receiving a reflected FMCW radar signal being the transmitted signal that has been reflected by the reflecting surface. Further, the method comprises the steps of providing a beat signal having a frequency that is equal to the frequency difference between the transmitted signal and the received signal and determining harmonics of the beat signal. The method also comprises the step of using phase shift information of at least one of said harmonics for determining a distance between the radar system and the reflecting surface.

Claims

1. A method, comprising:

transmitting, using a signal generator and antenna of a radar system, a frequency modulated continuous wave (FMCW) radar signal from the radar system;

receiving, by the radar system, a reflected FMCW radar signal corresponding to the transmitted FMCW radar signal that has been reflected by a reflecting surface;

obtaining, using a mixer of the radar system, a beat signal having a frequency corresponding to a frequency difference between the transmitted FMCW radar signal and the reflected FMCW radar signal;

determining harmonics of the beat signal by Fourier decomposition; and

determining, by a processor of the radar system, a distance between the radar system and the reflecting surface using phase shift information of at least one of the harmonics, wherein determining the distance comprises determining a phase difference between a pair of the harmonics.

2. The method according to claim 1, wherein determining the distance comprises determining multiple phase differences.

3. The method according to claim 1, further comprising setting an angular sweep frequency such that a particular phase shift in at least one of the harmonics or a particular differential phase shift between two of the harmonics corresponds to a pre-determined distance between the radar system and the reflecting surface.

4. The method according to claim 3, wherein the angular sweep frequency is set such that one of the pair of the harmonics reaches a peak at the pre-determined distance between the radar system and the reflecting surface.

5. The method according to claim 1, further comprising checking whether subsequent detected distances correspond with an expected distance evolution.

6. The method according to claim 1, further comprising checking a signal to noise ratio of the phase shift information prior to determining the distance.

7. The method according to claim 6, wherein determining the distance is started when the signal to noise ratio of the phase shift information exceeds a predetermined level.

8. The method according to claim 6, wherein checking the signal to noise ratio of the phase shift information comprises distributing calculated differential phases over K sets, low-pass filtering the K sets, selecting a reference set, among the K sets, having a highest value for computing a signal strength, and computing a noise strength measured in at least one of the K sets, wherein K is a positive integer.

9. The method according to claim 1, wherein determining the distance comprises detecting a differential phase shift, the differential phase shift being a shift in the phase difference between the pair of the harmonics.

10. The method according to claim 9, wherein the differential phase shift occurs when a harmonic of the pair of the harmonics reaches a peak.

11. A radar system, comprising:

a transmitter, comprising a signal generator and antenna, the transmitter configured to transmit a frequency modulated continuous wave (FMCW) radar signal;

a receiver configured to receive a reflected FMCW radar signal corresponding to the transmitted FMCW radar signal that has been reflected by a reflecting surface; and

a processing unit, comprising a mixer and processor, the processing unit configured to;

obtain, using the mixer, a beat signal having a frequency corresponding to a frequency difference between the transmitted FMCW radar signal and the reflected FMCW radar signal;

determine harmonics of the beat signal by Fourier decomposition; and

determine, using the processor, a distance between the radar system and the reflecting surface using phase shift information of at least one of the harmonics, wherein determining the distance comprises determining a phase difference between a pair of the harmonics.

12. The radar system of claim 11, wherein determining the distance comprises determining multiple phase differences.

13. The radar system of claim 11, wherein the processing unit is further configured to set an angular sweep frequency such that a particular phase shift in at least one of the harmonics or a particular differential phase shift between two or the harmonics corresponds to a pre-determined distance between the radar system and the reflecting surface.

14. The radar system of claim 11, wherein determining the distance is started when a signal to noise ratio of the phase shift information exceeds a predetermined level.

15. A non-transitory computer readable storage medium having computer-executable instructions stored therein that, when executed by a processor of a processing unit of a radar system that comprises a signal generator, antenna, and mixer, cause the processing unit to:

obtain, from the mixer, a beat signal having a frequency that corresponds to a frequency difference between a frequency modulated continuous wave (FMCW) radar signal, transmitted using the signal generator and antenna of the radar system, and a reflected FMCW radar signal corresponding to the transmitted FMCW radar signal that has been reflected by a reflecting surface;

determine harmonics of the beat signal by Fourier decomposition; and

determine a distance between the radar system and the reflecting surface using phase shift information of at least one of the harmonics, wherein determining the distance comprises determining a phase difference between a pair of the harmonics; and

output the distance between the radar system and the reflecting surface.

16. The non-transitory computer readable storage medium of claim 15, wherein determining the distance comprises determining multiple phase differences.

17. The non-transitory computer readable storage medium of claim 15, wherein the computer-executable instructions, when executed, further cause the processing unit to set an angular sweep frequency such that a particular phase shift in at least one of the harmonics or a particular differential phase shift between two of the harmonics corresponds to a pre-determined distance between the radar system and the reflecting surface.

18. The non-transitory computer readable storage medium of claim 15, wherein determining the distance is started when a signal to noise ratio of the phase shift information exceeds a predetermined level.