Radar apparatus for detecting a direction of a center of a target

Abstract

A radar apparatus of an automotive vehicle includes a radar unit which radiates an electromagnetic wave to a target in a forward direction of the vehicle and receives reflection beams from the target to detect the target. A scanning control unit performs a beam scanning of the radar unit to the target so that the reflection beams during the beam scanning are received. A center direction determining unit detects a distribution pattern of the received reflection beams with respect to respective scanning angles of the radar unit, performs a similarity approximation of the distribution pattern by using an antenna directional gain pattern of the radar unit to produce an approximated distribution pattern, and determines a direction of a center of the target based on a peak of the approximated distribution pattern.

What is claimed is:  
     
       1. A radar apparatus of an automotive vehicle, comprising: 
       radar means for radiating an electromagnetic wave to a target in a forward direction of the vehicle and for receiving reflection beams from the target to detect the target;  
       scanning control means for performing a beam scanning of the radar means to the target so that the reflection beams during the beam scanning are received; and  
       center direction determining means for detecting a distribution pattern of the received reflection beams with respect to respective scanning angles of the radar means, for performing a similarity approximation of the distribution pattern by using an antenna directional gain pattern of the radar means to produce an approximated distribution pattern, and for determining a direction of a center of the target based on a peak of the approximated distribution pattern.  
     
     
       2. The radar apparatus according to  claim 1 , further comprising: 
       correcting means for determining a corrected center scanning angle from a reference range value corresponding to a beam scanning range of the radar means for a width of the target, and from a scanning angle of the radar means corresponding to a mid-point of lower and upper limits of the scanning angle in the distribution pattern, when the vehicle is running along a curved path and the beam scanning range is below the reference range value.  
     
     
       3. The radar apparatus according to  claim 2 , wherein said correcting means includes: 
       means for detecting whether the vehicle is running along a curved path, by comparing a radius of curvature of a present path along which the vehicle is presently running with a predetermined reference value, said radius of curvature being determined by using a measured yaw rate and a measured vehicle speed.  
     
     
       4. The radar apparatus according to  claim 2 , wherein said correcting means includes: 
       means for detecting whether a beam radiation axis of the radar means directed to the target is slanting with respect to the forward direction of the vehicle.  
     
     
       5. The radar apparatus according to  claim 1 , wherein, when the vehicle is not running along a curved path, said center direction determining means generates a signal indicating the direction of the center of the target for a center scanning angle of the radar means. 
     
     
       6. The radar apparatus according to  claim 1 , wherein, when a beam radiation axis of the radar means directed to the target is not slanting with respect to the forward direction of the vehicle, said center direction determining means generates a signal indicating the direction of the center of the target for a center scanning angle of the radar means. 
     
     
       7. The radar apparatus according to  claim 1 , further comprising: 
       alarm means for providing a warning of a dangerous condition of the vehicle to a vehicle operator when the vehicle is detected to be in the dangerous condition with respect to the target, based a relative distance of the target and a relative velocity of the target.  
     
     
       8. The radar apparatus according to  claim 1 , wherein said radar apparatus includes a yaw rate sensor connected to an electronic control unit, said yaw rate sensor measuring a yaw rate of the vehicle and supplying the measured yaw rate to the electronic control unit. 
     
     
       9. The radar apparatus according to  claim 1 , wherein said radar apparatus includes a vehicle speed sensor connected to an electronic control unit, said vehicle speed sensor measuring a vehicle speed of the vehicle and supplying the measured vehicle speed to the electronic control unit. 
     
     
       10. The radar apparatus according to  claim 1 , wherein said radar means is a frequency-modulation-continuous-wave radar unit which radiates an extremely-high-frequency electromagnetic wave. 
     
     
       11. A radar apparatus for an automotive vehicle in which a radiation beam from a radar unit is transmitted to a target in a forward direction of the vehicle and reflection beams from the target are received so that a relative distance between the target and the vehicle and a relative velocity of the target are detected based on the reflection beams, said radar apparatus comprising: 
       
         a frequency modulation unit for modulating a frequency of a radiation signal related to the radiation beam, in accordance with a predetermined waveform;  
       
         a beat signal generating unit for generating a first beat signal from the reflection beams during an up - period for which the frequency of the radiation signal is increasing and a second beat signal from the reflection beams during a down - period for which the frequency of the radiation signal is decreasing;    
       
         a radar signal processing unit for determining spectrum level data, including a first spectrum level of frequency of the first beat signal and a second spectrum level of frequency of the second beat signal, so that the relative distance and the relative velocity related to the target are determined based on a pairing of a peak in the first spectrum level and a peak in the second spectrum level;  
       
       
         a scanning controller for performing a beam scanning of the radar unit to the target with respect to a specific one of a plurality of scanning ranges to that the reflection beams with respect to each of the plurality of scanning ranges are received; and  
       
       
         a radar control unit for performing the pairing of the spectrum level peaks for the spectrum level data from the radar signal processing unit, based on the specific scanning range related to the spectrum level peaks when two or more pairs of peaks in the first spectrum level and in the second spectrum level, related to a plurality of targets, are included in the spectrum level data for the specific scanning range. 
       
     
     
       12. The radar apparatus according to  claim 11 , wherein said radar control unit makes a determination as to whether the pairing of the spectrum level peaks for the spectrum level data is appropriately performed, by comparing a correlation factor of the spectrum level data related to the specific one of the plurality of scanning ranges with a threshold value. 
     
     
       13. The radar apparatus according to  claim 12 , wherein said radar control unit stores the spectrum level data for the specific scanning range into one of a plurality of predetermined areas of a memory when it is determined that the correlation factor is not above the threshold value. 
     
     
       14. The radar apparatus according to  claim 11 , wherein, when the spectrum level data is stored in one of a plurality of predetermined areas of a memory, said radar control unit makes a determination as to whether the spectrum level data has been fixed to determine the relative distance and the relative velocity related to a respective one of the plurality of targets. 
     
     
       15. The radar apparatus according to  claim 11 , wherein, when said radar control unit has determined that the spectrum level data has been fixed, said radar control unit makes a determination as to whether the spectrum level peaks for the spectrum level data stored in one of a plurality of predetermined areas of a memory are the same as the spectrum level peaks for the spectrum level data stored in an adjacent one of the plurality of predetermined areas. 
     
     
       16. The radar apparatus according to  claim 11 , wherein, when said radar control unit has determined that the spectrum level peaks for the spectrum level data stored in one of a plurality of predetermined areas of a memory are the same as the spectrum level peaks for the spectrum level data stored in an adjacent one of the plurality of predetermined areas, said radar control unit performs the pairing of the spectrum level peaks for the spectrum level data stored in said one of the plurality of predetermined areas. 
     
     
       17. The radar apparatus according to  claim 11 , wherein said radar control unit makes a determination as to whether two or more pairs of peaks in the first spectrum level and in the second spectrum level, related to the plurality of targets, are included in the spectrum level data. 
     
     
       18. The radar apparatus according to  claim 11 , wherein said radar control unit determines values of the relative distance and the relative velocity with respect to each of the plurality of targets for the specific scanning range and stores the relative distance values, the relative velocity values and the specific ranges of the beam scanning related to each of the plurality of targets. 
     
     
       19. The radar apparatus according to  claim 11 , wherein said radar apparatus includes a steering angle sensor connected to an electronic control unit, said steering angle sensor outputting a measured steering angle of the vehicle to the electronic control unit. 
     
     
       20. The radar apparatus according to  claim 11 , wherein said radar apparatus includes a yaw rate sensor connected to an electronic control unit, said yaw rate sensor outputting a signal indicating a measured yaw rate of the vehicle to the electronic control unit. 
     
     
       21. The radar apparatus according to  claim 11 , wherein said radar apparatus includes a vehicle speed sensor connected to an electronic control unit, said vehicle speed sensor outputting a signal indicating a measured speed of the vehicle to the electronic control unit. 
     
     
       22. The radar apparatus according to  claim 11 , wherein said radar apparatus includes a frequency- modulation - continuous - wave radar unit which radiates an extremely - high - frequency electromagnetic wave as the radiation beam.