Radar apparatus

• US 6,573,859 B2
• Filed: 01/02/2001
• Issued: 06/03/2003
• Est. Priority Date: 02/07/2000
• Status: Expired due to Fees

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Tokoro, Setsuo
• Primary Examiner(s): Gregory, Bernarr E.
• Application Number:
  US09/750,920
• Publication Number:
  US 20010015698A1
• Time in Patent Office: 882 Days
• Field of Search: 342/70, 342/71, 342/72, 342/118, 342/128, 342/133, 342/134, 342/139, 342/145-158, 342/175, 342/194-197, 342/385, 342/417-499, 342/100, 342/113, 342/165-174, 342/27, 342/28
• US Class Current: 342/70
• CPC Class Codes: G01S 13/345 using triangular modulation
• CPC Class Codes: G01S 13/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S13/46
• CPC Class Codes: G01S 13/931 of land vehicles
• CPC Class Codes: G01S 2013/932 using own vehicle data, e.g. ground speed, steering wheel direction
• CPC Class Codes: G01S 2013/93271 in the front of the vehicles
• 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 radar apparatus of the present invention is provided with a reception array antenna having a plurality of antenna elements, a first bearing detector for detecting a bearing of a target by carrying out signal processing on individual element signals received on an element-by-element basis through the respective antenna elements, and a second bearing detector for detecting a bearing of a target by carrying out signal processing different from that of the first bearing detector, on the individual element signals received through the respective antenna elements. Since the radar apparatus is provided with the two detectors of the first bearing detector and second bearing detector as means for acquiring the target bearing, both or either one of the results of detection by the two detectors can be selectively utilized as occasion demands.

Claims

1. A radar apparatus comprising:

a transmitter for outputting a local signal;

a reception array antenna having a plurality of antenna elements;

a receiver coupled to the plurality of antenna elements for receiving the local signal; and

a processor coupled to an output of the receiver, said processor comprising;

first bearing detecting means for detecting a bearing of a target by carrying out signal processing on individual element signals received on an element-by-element basis through said respective antenna elements; and

second bearing detecting means for detecting a bearing of a target by carrying out signal processing different from that of said first bearing detecting means, on the individual element signals received through said respective antenna elements.

2. The radar apparatus according to claim 1,

wherein said first bearing detecting means imposes a lighter operational load for detection of the target bearing than said second bearing detecting means, and

wherein said second bearing detecting means possesses a higher target bearing resolution than said first bearing detecting means.

3. The radar apparatus according to claim 2, wherein said first bearing detecting means is applied to detection of a target existing in a relatively near range and said second bearing detecting means to detection of a target existing in a relatively far range.

4. The radar apparatus according to claim 3, wherein a transmitted signal of frequency-modulated continuous wave is used and the distance to the target is acquired from a beat frequency between said transmitted signal and a received signal through said reception array antenna.

5. The radar apparatus according to claim 4, comprising a reception circuit for mixing said transmitted signal with the received signals received through said plurality of antenna elements to acquire beat signals and converting the beat signals obtained corresponding to said respective antenna elements, to digital beat signals,

wherein said first bearing detecting means is means for carrying out a digital beamforming process on said plurality of element-by-element digital beat signals to form an antenna beam in a plurality of directions and detecting the bearing of said target, and

wherein said second bearing detecting means is means for carrying out an analysis by digital signal processing on a phase difference between said plurality of element-by-element digital beat signals to detect the bearing of said target as point information.

6. The radar apparatus according to claim 5, wherein said first bearing detecting means detects the bearing of said target, using a frequency component of the beat frequency not more than a predetermined value out of said element-by-element digital beat signals, and

wherein said second bearing detecting means detects the bearing of said target, using a frequency component of the beat frequency larger than said predetermined value out of said element-by-element digital beat signals.

7. The radar apparatus according to claim 6, comprising beat frequency detecting means for detecting a beat frequency indicating an approximate distance at which a target is assumed to exist, prior to the detection of the bearing of the target by said first baring detecting means or by said second bearing detecting means.

8. The radar apparatus according to claim 7, wherein at least either one of said first bearing detecting means and said second bearing detecting means is means for carrying out said target bearing detection with a limitation to the beat frequency component acquired by said beat frequency detecting means.

9. The radar apparatus according to claim 5, wherein said first bearing detecting means is means for detecting the bearing of said target from a position of a peak in a power distribution with a variable of bearing and detecting a width of said target from a width of the distribution at a position where power is lowered by a predetermined amount from said peak position.

10. The radar apparatus according to claim 9, wherein when the target width detected by said first bearing detecting means is not less than a predetermined value, the bearing of the target is again detected at the same beat frequency by said second bearing detecting means.

11. The radar apparatus according to claim 5, wherein said second bearing detecting means is means for detecting the target bearing by an analytical operation using an adaptive array antenna filter and wherein initial values of weights in said analytical operation are set based on the result of recognition by said first bearing detecting means.

12. The radar apparatus according to claim 5, wherein said second bearing detecting means is means for detecting the target bearing by an analytical operation using an adaptive array antenna filter and wherein initial values of weights in said analytical operation are set based on the result of target recognition in previous detection.

13. The radar apparatus according to claim 4, which comprises:

a reception circuit for mixing said transmitted signal with the received signals received through said plurality of antenna elements to acquire beat signals and converting the beat signals obtained corresponding to said respective antenna elements, to digital beat signals, and

beat frequency detecting means for detecting a beat frequency indicating an approximate distance at which a target is assumed to exist,

wherein each of said first and second bearing detecting means is means for carrying out a digital beamforming process on a predetermined frequency component of said plurality of element-by-element digital beat signals to form an antenna beam in a plurality of directions and detecting the bearing of said target,

wherein said first bearing detecting means performs the digital beamforming process for a frequency detected by said beat frequency detecting means and being not more than a predetermined frequency or for a frequency near said frequency, and

wherein said second bearing detecting means is means for performing the digital beamforming process for all frequencies from said predetermined frequency to a maximum frequency of a detection range.

14. The radar apparatus according to claim 13, which is mounted on a vehicle, said vehicle comprising lane shape acquiring means for acquiring a shape of a lane on which said vehicle is running,

wherein when it is determined that a target detected is present on the lane acquired by said lane shape acquiring means, said first and second bearing detecting means suspend the digital beamforming process based on the beat signal acquired at that time for beat frequencies larger than a beat frequency corresponding to that target.

15. The radar apparatus according to claim 4, comprising a reception circuit for mixing said transmitted signal with the received signals received through said plurality of antenna elements to acquire beat signals and converting the beat signals obtained corresponding to said respective antenna elements, to digital beat signals,

wherein said first and second bearing detecting means are means for carrying out a digital beamforming process on said plurality of element-by-element digital beat signals to form an antenna beam in a plurality of directions and detecting the bearing of said target, and

wherein the number of said antenna beams formed per unit angle in said first bearing detecting means is smaller than the number of said antenna beams formed per unit angle in said second bearing detecting means.

16. The radar apparatus according to claim 15, wherein said first bearing detecting means performs the digital beamforming process on a frequency component not more than a predetermined value out of said plurality of element-by-element digital beat signals, and

wherein said second bearing detecting means performs the digital beamforming process on a frequency component larger than said predetermined value out of said plurality of element-by-element digital beat signals.

17. The radar apparatus according to claim 15, comprising beat frequency detecting means for detecting a beat frequency indicating an approximate distance at which a target is assumed to exist,

wherein said first and second bearing detecting means perform said digital beamforming process with a limitation to the beat frequency component detected by said beat frequency detecting means.