Method for Detecting a Distance, a Radar System and a Computer Program Product

• US 20120169529A1
• Filed: 06/17/2010
• Published: 07/05/2012
• Est. Priority Date: 06/17/2009
• Status: Active Grant

• Current Assignee: Nederlandse Organisatie Voor Toegepast-Natuurwetenschappelijk Onderzoek Tno
• Original Assignee: Nederlandse Organisatie Voor Toegepast
• Inventors: Prevo, René, Janssen, Johannes Antonius Andreas, van Heijster, Robért Michael Evert
• Granted Patent: US 9,310,476 B2
• Time in Patent Office: Days
• US Class Current: 342/128
• 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 for detecting a distance between a radar system and a reflecting surface, comprising the steps of:

transmitting a frequency modulated continuous wave (FMCW) radar signal from the radar system;

receiving a reflected FMCW radar signal being the transmitted signal that has been reflected by the reflecting surface;

providing a beat signal having a frequency that is equal to the frequency difference between the transmitted signal and the received signal;

determining harmonics of the beat signal by Fourier decomposition; and

using phase shift information of at least one of said harmonics for determining a distance between the radar system and the reflecting surface.

2. A method according to claim 1, wherein the step of using phase shift information comprises determining a phase difference between a pair of harmonics.

3. A method according to claim 2, wherein the step of using phase shift information comprises determining multiple phase differences.

4. A method according to claim 1, further comprising setting an angular sweep frequency so as to allow a particular associated phase shift in a harmonic or between harmonics to correspond to a pre-determined distance between the radar system and the reflecting surface.)

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

6. A method according to claim 1, further comprising checking a signal to noise ratio of the phase shift information prior to detecting a height.

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

8. A method according to claim 6, wherein a signal to noise ratio of the phase shift information is determined by distributing calculated differential phases over K sets, low-pass filtering the K sets, selecting a reference set having a highest value for computing a signal strength, and computing a noise strength measured in the sets.

9. A radar system for detecting a distance to a reflecting surface, comprising:

a transmitter module arranged for transmitting a frequency modulated continuous wave (FMCW) radar signal;

receiver module arranged for receiving a reflected FMCW radar signal being the transmitted signal that has been reflected by the reflecting surface; and

a processing unit arranged for;

providing a beat signal having a frequency that is equal to the frequency difference between the transmitted signal and the received signal;

determining harmonics of the beat signal by Fourier decomposition; and

using phase shift information of at least one of said harmonics for determining a distance between the radar system and the reflecting surface.

10. A computer program product for detecting a distance between a radar system and a reflecting surface, which computer program product comprises instructions for causing a processing unit to perform the steps of:

providing a beat signal having a frequency that is equal to the frequency difference between a frequency modulated continuous waves (FMCW) radar signal being transmitted by the radar system and a received FMCW radar signal being the transmitted signal that has been reflected by the reflecting surface;

determining harmonics of the beat signal by Fourier decomposition; and

using phase shift information of at least one of said harmonics for determining a distance between the radar system and the reflecting surface.