Method for LFM radar accuracy improvement without increasing FFT length

• US 10,444,325 B2
• Filed: 12/09/2016
• Issued: 10/15/2019
• Est. Priority Date: 12/09/2016
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: Pokrass, Alexander, Laifenfeld, Moshe, Bilik, Igal
• Primary Examiner(s): Brainard, Timothy A
• Application Number:
  US15/374,193
• Publication Number:
  US 20180164405A1
• Time in Patent Office: 1,040 Days
• Field of Search: 342 70
• CPC Class Codes: G01S 13/931 of land vehicles
• CPC Class Codes: G01S 7/288 Coherent receivers
• CPC Class Codes: G01S 7/2883 using FFT processing
• CPC Class Codes: G01S 7/2921 based on data belonging to one radar period
• CPC Class Codes: G01S 7/352 Receivers
• CPC Class Codes: G01S 7/354 Extracting wanted echo-signals Doppler systems G01S13/50
• CPC Class Codes: G01S 7/356 involving particularities of FFT processing

Abstract

A method and apparatus for determining a frequency of an echo signal obtained by a radar system is disclosed. The echo signal in response to a source signal of the radar system is received at a receiver. A harmonic oscillator generates a harmonic component signal, and a multiplier multiplies the echo signal with the harmonic component signal to obtain a combined signal. A Fast Fourier Transform (FFT) is performed on the combined signal to obtain a peak in a frequency space, wherein a central frequency of a frequency bin in the frequency space is shifted with respect to the frequency of the echo signal by the harmonic component signal. The frequency of the echo signal is determined from the shifted central frequency.

Claims

1. A method of determining a frequency of an echo signal obtained by a radar system, comprising:

receiving the echo signal at a receiver in response to a source signal of the radar system;

multiplying the echo signal by a harmonic component signal to obtain a combined signal; and

performing, on a processor, a Fast Fourier Transform (FFT) on the combined signal to obtain a peak in a frequency space, wherein a central frequency of a frequency bin in the frequency space is shifted with respect to the frequency of the echo signal by the harmonic component signal; and

determining the frequency of the echo signal from the shifted central frequency.

2. The method of claim 1, wherein the harmonic component signal is a complex harmonic signal.

3. The method of claim 2, wherein a frequency Ω

of the complex harmonic signal is equal to a fraction of a frequency resolution of the FFT.

4. The method of claim 3, wherein Ω

=Δ

F/k, where Δ

F is a frequency resolution of the frequency space for the FFT and k is a resolution factor.

5. The method of claim 3, wherein the central frequency of the frequency bin is shifted in frequency space by the frequency Ω

.

6. The method of claim 3, further comprising adjusting the harmonic frequency Ω

based on a result of the FFT.

7. The method of claim 1, further comprising providing the frequency measurement to a collision avoidance device of a vehicle.

8. The method of claim 7, wherein the determined frequency indicates at least one of a location and a velocity of a target with respect to the vehicle, further comprising operating the collision avoidance device to maneuver the vehicle with respect to the target based on the determined frequency.

9. An apparatus for determining a frequency of an echo signal obtained using radar, comprising:

a receiver configured to receive the echo signal in response to reflection of a source signal generated by the radar from a target;

a harmonic oscillator configured to generate a harmonic component signal;

a multiplier for multiplying the echo signal with the harmonic component signal to obtain a combined signal; and

a processor configured to;

perform a Fast Fourier Transform (FFT) on the combined signal to obtain a peak in a frequency space, wherein a central frequency of a frequency bin in the frequency space is shifted with respect to the frequency of the echo signal, and

determine the frequency of the echo signal from the shifted central peak.

10. The apparatus of claim 9, wherein the harmonic component signal is a complex harmonic signal.

11. The apparatus of claim 10, wherein a frequency Ω

of the complex harmonic signal is equal to a fraction of a frequency resolution of the FFT.

12. The apparatus of claim 11, wherein Ω

=Δ

F/k, where Δ

F is a frequency resolution of the frequency space for a selected FFT and k is a resolution factor.

13. The apparatus of claim 11, wherein the central frequency of the frequency bin is shifted in frequency space by frequency Ω

.

14. The apparatus of claim 11, further comprising a frequency tuner that adjusts the harmonic frequency Ω

of the harmonic oscillator based on a result of the FFT.

15. The apparatus of claim 9, further comprising a vehicle including a collision avoidance device that operates using the frequency measurement.

16. The apparatus of claim 15, wherein the determined frequency indicates at least one of a location and a velocity of a target with respect to the vehicle, and the collision avoidance device maneuvers the vehicle with respect to the target based on the determined frequency.