Separation of close targets based on Doppler precoding

• US 10,444,348 B2
• Filed: 08/17/2017
• Issued: 10/15/2019
• Est. Priority Date: 08/17/2017
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (Motors Liquidation Co. GUC Trust)
• Inventors: Bialer, Oded
• Primary Examiner(s): Chen, Shelley
• Application Number:
  US15/679,572
• Publication Number:
  US 20190056490A1
• Time in Patent Office: 789 Days
• Field of Search: None
• CPC Class Codes: G01S 13/18 wherein range gates are used
• CPC Class Codes: G01S 13/50 Systems of measurement based on relative movement of target
• CPC Class Codes: G01S 13/931 of land vehicles
• CPC Class Codes: G01S 13/935 for terrain-avoidance
• CPC Class Codes: G01S 2013/93271 in the front of the vehicles

Abstract

A system and method to separate close targets includes transmitting a pulse sequence and detecting a first target at a first target Doppler frequency based on processed received reflections resulting from the pulse sequence. A nulling pulse sequence designed to null the processed received reflections at the target Doppler frequency is transmitted.

Claims

1. A method of separating close targets, the method comprising:

transmitting a pulse sequence;

detecting a first target at a first target Doppler frequency based on processed received reflections resulting from the pulse sequence; and

transmitting a nulling pulse sequence designed to null the processed received reflections at the target Doppler frequency.

2. The method according to claim 1, further comprising detecting a second target having a lower reflectivity than the target based on the processed received reflections resulting from the nulling pulse sequence.

3. The method according to claim 1, further comprising generating the pulse sequence to have a constant phase.

4. The method according to claim 1, wherein the detecting the first target includes forming a matrix of received sequences a(f_i) for Doppler frequencies f_i of f₀ through f_L given by:

A=[a(f₀)a(f₁) . . . a(f_L)].

5. The method according to claim 4, wherein the detecting the first target includes determining each of the received sequences a(f_i) for sampling time intervals T₀ through T_L as:

a(f_i)=[e<sup>j2π

fiT0</sup> e<sup>j2π

fiT1</sup> . . . e<sup>j2π

fiTL</sup>]^T, where

T indicates a transpose to a column vector.

6. The method according to claim 5, further comprising generating the nulling pulse sequence includes generating a binary vector b of length L+1.

7. The method according to claim 6, wherein the generating the binary vector b includes setting every element of the binary vector b to 1 except the element corresponding with the target Doppler frequency of the first target.

8. The method according to claim 6, wherein the generating the nulling pulse sequence is according to:

w=arg min_{{tilde over (w)}}∥

A{tilde over (w)}−

b∥

², where

w is the null pulse sequence.

9. The method according to claim 8, further comprising solving for the nulling pulse sequence as:

w=(A^HA)<sup>−

1</sup>A^Hb, where

H represents a Hermitian transpose.

10. The method according to claim 1, further comprising transmitting the pulse sequence again following the transmitting the nulling pulse sequence.

11. A system to separate close targets, the system comprising:

a radar system configured to transmit a pulse sequence; and

a controller configured to detect a first target at a first target Doppler frequency based on processed received reflections resulting from the pulse sequence and to generate a nulling pulse sequence designed to null the processed received reflections at the target Doppler frequency.

12. The system according to claim 11, wherein the controller is further configured to detect a second target having a lower reflectivity than the target based on the processed received reflections resulting from the nulling pulse sequence.

13. The system according to claim 11, wherein the controller is further configured to generate the pulse sequence to have a constant phase.

14. The system according to claim 11, wherein the controller is further configured to detect the first target based on forming a matrix of received sequences a(f_i) for Doppler frequencies f_i of f₀ through f_L given by:

A=[a(f₀)a(f₁) . . . a(f_L)].

15. The system according to claim 14, wherein the controller is further configured to detect the first target based on determining each of the received sequences a(f_i) for sampling time intervals T₀ through T_L as:

a(f_i)=[e<sup>j2π

fiT0</sup> e<sup>j2π

fiT1</sup> . . . e<sup>j2π

fiTL</sup>]^T, where

T indicates a transpose to a column vector.

16. The system according to claim 15, wherein the controller is further configured to generate the nulling pulse sequence based on generating a binary vector b of length L+1.

17. The system according to claim 16, wherein the controller is further configured to generate the binary vector b based on setting every element of the binary vector b to 1 except the element corresponding with the target Doppler frequency of the first target.

18. The system according to claim 16, wherein the controller is further configured to generate the nulling pulse sequence according to:

w=arg min_{{tilde over (w)}}∥

A{tilde over (w)}−

b∥

², where

w is the null pulse sequence.

19. The system according to claim 18, wherein the controller is further configured to solve for the nulling pulse sequence as:

w=(A^HA)<sup>−

1</sup>A^Hb, where

H represents a Hermitian transpose.

20. The system according to claim 11, wherein the radar system is further configured to transmit the pulse sequence again following transmitting the nulling pulse sequence.