Radar method for measuring distances between and relative speeds of a vehicle and one or more obstacles

• US 6,396,436 B1
• Filed: 04/07/2000
• Issued: 05/28/2002
• Est. Priority Date: 04/07/1999
• Status: Expired due to Term

• Current Assignee: Volkswagen AG
• Original Assignee: Volkswagen AG
• Inventors: Meinecke, Marc-Michael, Lissel, Ernst, Rohling, Hermann
• Primary Examiner(s): Gregory, Bernarr E.
• Application Number:
  US09/545,528
• Time in Patent Office: 781 Days
• Field of Search: 342/70-72,104-115,118,127-133,192-197,165
• US Class Current: 342/70
• 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 13/931 of land vehicles

Abstract

The present invention relates to a CW radar method for measuring distances between and relative speeds of a vehicle and one or more obstacles. The present invention further provides that the transmission (s(t)) can be composed of at least four consecutive chirps (A, B, C, D), each having different slopes. The intersection points of all lines in the distance-relative speed diagram from two chirps (A, B) can be calculated from all the ascertained frequency positions K_1,n and K_2,p. To validate those intersection points, one may observe whether a peak exists in the Fourier spectrum of a third chirp C at a frequency position K_3,q, whose assigned line intersects a surrounding area of the intersection point in the distance-relative speed diagram. A further validation of those intersection points involves observing whether a peak exists in the Fourier spectrum of a fourth chirp D at a frequency position K_4,r, whose assigned line intersects a surrounding area of the intersection point in the distance-relative speed diagram. The intersection points are then regarded as valid, when they satisfy both conditions.

Claims

1. A radar method for measuring distances between and relative speeds of a vehicle and one or more obstacles, comprising:

emitting a transmission signal, the transmission signal being generated using an oscillator and having a sequence of linear chirps, and

simultaneously receiving a receiving signal, the receiving signal being reflected at at least one obstacle during the emission of the transmission signal;

acquiring a mixer output signal resulting from mixing the receiving signal with the transmission signal in a mixer;

processing the mixer output signal in a signal processing device (9) to obtain at least one signal value for at least one distance (R_i) of the at least one obstacle to the vehicle and for at least one relative speed (v_Rel,i) of the vehicle and any detected at least one obstacle;

analyzing the mixer output signal for each chirp of the transmission signal using a Fourier transform resulting in a spectrum, and

calculating the respective frequency position K_i of each of the at least one obstacle as a respective at least one peak in the Fourier transform spectrum;

providing a sequence of the transmission signal with at least four consecutive chirps (A, B, C, D) having respective slopes (m₁, m₂, m₃, m₄), each of the at least four consecutive chirps (A, B, C, D) being different in value for each of the sequence of the transmission signal;

calculating at least one intersection point at the at least one distance R_i of the at least one obstacle to the vehicle and the at least one relative speed v_rel,i of the vehicle and the any detected at least one obstacle, the intersection points being from any lines resulting from two of the chirps (A, B) and being calculated from the frequency positions K_1,n and K_2,p in the distance-relative speed diagram;

checking a first condition to determine whether a peak in the Fourier spectrum of the third chirp (C) exists at a frequency position K_3,q, whose assigned line in the distance-relative speed diagram intersects a surrounding area of the intersection point (R_i, v_rel,i);

checking a second condition to determine whether a peak in the Fourier spectrum of the fourth chirp (D) exists at a frequency position K_4,r, whose assigned line in the distance-relative speed diagram intersects a surrounding area of the intersection point (R_i, v_rel,i); and

validating the intersection points (R_i, v_rel,i) as valid when the first and the second conditions are checked and determined satisfied.

2. The method as recited in claim 1, respectively, wherein the intersection points (R_i, v_rel,i) of all lines from the first two chirps (A, B) are calculated from all the ascertained frequency positions K_1,n and K_2,p according to the equations $R_i=\Delta$



 



R·

κ

2,p-κ

1,nm1-m2,

vRe

 



l,i=Δ



 



v·

m1

κ

2,p-m2

κ

1,nm1-m2,

where Δ

R signifies the distance resolution and where Δ

v signifies the resolution of the speed.

3. The method as recited in claim 1 or 2, wherein the calculated intersection points (R_i, v_Rel,i) are checked to determine whether a peak in the Fourier spectrum of a third chirp (C) exists at a frequency position K_3,q, for which $k_{3,q}-{\varepsilon }_{}$

1≤

(vRe

 



l,iΔ



 



v-m3·

RiΔ



 



R)≤

k3,q+ɛ

1

is valid, where ε

₁ represents a parameter of predefined magnitude.

4. The method as recited in claim 3, wherein the intersection points (R_i, v_Rel,i) are checked to determine whether a peak in the Fourier spectrum of a fourth chirp (D) exists at a frequency position K_4,r, for which $k_{4,r}-{\varepsilon }_{}$

2≤

(vRe

 



l,iΔ



 



v-m4·

RiΔ



 



R)≤

k4,r+ɛ

2

is valid, where ε

₂ represents a parameter of predefined magnitude.

5. The method as recited in claim 4, wherein the values of the parameters ε

₁ and ε

₂ are in the range of 0.3 to 0.7.

6. The method as recited in claim 4, wherein the values of the parameters ε

₁ and ε

₂ are in the range of 0.4 to 0.6.

7. The method as recited in claim 4, wherein the values of the parameters ε

₁ and ε

₂ are each 0.5.

8. The method as recited in claim 4, wherein the values of the parameters ε

₁ and ε

₂ are equal.

9. The method as recited in claim 3, wherein the values of the parameters ε

₁ and ε

₂ are in the range of 0.3 to 0.7.

10. The method as recited in claim 3, wherein the values of the parameters ε

₁ and ε

₂ are in the range of 0.4 to 0.6.

11. The method as recited in claim 3, wherein the values of the parameters ε

₁ and ε

₂ are each 0.5.

12. The method as recited in claim 3, wherein the values of the parameters ε

₁ and ε

₂ are equal.

13. The method as recited in claim 1 or 2, wherein the intersection points (R_i, v_Rel,i) are checked to determine whether a peak in the Fourier spectrum of a fourth chirp (D) exists at a frequency position K_4,r, for which $k_{4,r}-{\varepsilon }_{}$

2≤

(vRe

 



l,iΔ



 



v-m4·

RiΔ



 



R)≤

k4,r+ɛ

2

is valid, ε

₂ representing a parameter of predefined magnitude.

14. The method as recited in claim 13, wherein the values of the parameters ε

₁ and ε

₂ are in the range of 0.3 to 0.7.

15. The method as recited in claim 13, wherein the values of the parameters ε

₁ and ε

₂ are in the range of 0.4 to 0.6.

16. The method as recited in claim 13, wherein the values of the parameters ε

₁ and ε

₂ are each 0.5.

17. The method as recited in claim 13, wherein the values of the parameters ε

₁ and ε

₂ are equal.

18. A radar device for measuring distances between and relative speed of a vehicle and at least one obstacle, comprising:

an arrangement configured to emit a transmission signal generated using an oscillator and including a sequence of linear chirps;

an arrangement configured to simultaneously receive a receiving signal reflected at at least one obstacle during the emission of the transmission signal;

an arrangement configured to acquire a mixer output signal resulting from mixing the receiving signal with the transmission signal in a mixer;

an arrangement configured to process the mixer output signal to obtain at least one signal value for at least one distance of the at least one obstacle to the vehicle and for at least one relative speed of the vehicle and any detected at least one obstacle;

an arrangement configured to analyze the mixer output signal for each chirp of the transmission signal using a Fourier transform resulting in a spectrum;

an arrangement configured to calculate the respective frequency position of each of the at least one obstacle as a respective at least one peak in the Fourier transform spectrum;

an arrangement configured to provide a sequence of the transmission signal with at least four consecutive chirps having respective slopes, each of the at least four consecutive chirps being different in value for each of the sequence of the transmission signal;

an arrangement configured to calculate at least one intersection point at the at least one distance of the at least one obstacle to the vehicle and the at least one relative speed of the vehicle and the any detected at least one obstacle, the intersection points being from any lines resulting from two of the chirps and being calculated from the frequency positions in the distance-relative speed diagram;

an arrangement configured to check a first condition to determine whether a peak in the Fourier spectrum of the third chirp exists at a frequency position, whose assigned line in the distance-relative speed diagram intersects a surrounding area of the intersection point;

an arrangement configured to check a second condition to determine whether a peak in the Fourier spectrum of the fourth chirp exists at a frequency position, whose assigned line in the distance-relative speed diagram intersects a surrounding area of the, intersection point; and

an arrangement configured to validate the intersection points as valid when the first and the second conditions are checked and determined satisfied.