Abstract:
A radar system for detecting a single object from a plurality of objects and calculating 4D information of said object may include a first radar for obtaining first positional information of a first object, a second radar for obtaining second positional information of a second object and a computer for comparing the first positional information with the second positional information to determine if the first object is the same as the second object and combining the matched first positional and second positional information into 4D information.

Description:
PRIORITY 
       [0001]    The present invention claims priority under 35 USC section 119 based upon a provisional application with a Ser. No. 61/890,267 which was filed on Oct. 13, 2013. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to a 4-dimensional (4D) continuous wave radar system which can provide 4D information of a moving object: range, range rate, azimuth angle and elevation angle. 
       BACKGROUND 
       [0003]    Traditionally, 3D information of a moving object (range, rage rate and azimuth angle) can be derived from a continuous wave radar which has multiple transmitting antennas and multiple receiving antennas using a waveform modulation method, such as Frequency Shift Keying (FSK) method or Frequency Modulated Continuous Wave (FMCW) method.  FIG. 1  presents an example of continuous wave radar with one transmitting antenna and two receiving antennas for 3-dimensional (3D) information sensing. The 3D information of the moving object is: range (r), range rate (v d ) and angle (θ). 
       SUMMARY 
       [0004]    A radar system for detecting a single object from a plurality of objects and calculating 4D information of said object may include a first radar for obtaining first positional information of a first object, a second radar for obtaining second positional information of a second object and a computer for comparing the first positional information with the second positional information to determine if the first object is the same as the second object and combining the matched first positional and second positional information into 4D information. 
         [0005]    The first radar may be a horizontal radar. 
         [0006]    The second radar may be a vertical radar. 
         [0007]    The first positional information may include range information. 
         [0008]    The second positional information may include range information. 
         [0009]    The first positional information may include azimuth angle information. 
         [0010]    The second positional information may include elevational angle information. 
         [0011]    The first positional information may include range rate information. 
         [0012]    The second positional information may include range rate information. 
         [0013]    The first positional information may be compared to the second positional information includes first range information from the first radar being compared to second range information from the second radar. 
         [0014]    The first positional information may be compared to the second positional information includes first range rate information from the first radar being compared to second range rate information from the second radar. 
         [0015]    The matched first positional information and second positional information may be combined into 4D information. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The invention may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which, like reference numerals identify like elements, and in which: 
           [0017]      FIG. 1  illustrates a continuous wave radar for three-dimensional information; 
           [0018]      FIG. 2  illustrates a 4D continuous wave radar of the present invention for a singular moving object; 
           [0019]      FIG. 3  illustrates a 4D continuous wave radar of the present invention for multiple moving objects; 
           [0020]      FIG. 4  illustrates a flowchart of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    In many applications, 4D information (range, range rate, azimuth and elevation angles) of a moving object is needed. No existing continuous wave radar device can provide such 4D information. The present invention presents a system using a horizontal 3D radar and a vertical 3D radar in a perpendicular configuration to derive 4D information of a moving object. Both horizontal and vertical radars could have multiple transmitters and receivers. 
         [0022]    The 4D information of the moving object can be derived by combining the 3D information from both horizontal and vertical radars. For a single moving object, this is trivial; but for multiple moving objects within both horizontal and vertical radar energy beams (as shown in  FIG. 3 ), a more challenging task is to find the signals in both horizontal and vertical radar corresponding to the same moving object. 
         [0023]    An example of deriving 3D information of a moving object is illustrated in  FIG. 1 . The range (distance) 
         [0000]    
       
         
           
             r 
             = 
             
               
                 c 
                  
                 
                     
                 
                  
                 Δ 
                  
                 
                     
                 
                  
                 ϕ 
               
               
                 4 
                  
                 
                     
                 
                  
                 π 
                  
                 
                     
                 
                  
                 Δ 
                  
                 
                     
                 
                  
                 f 
               
             
           
         
       
     
         [0000]    and range rate (speed) can be derived either using FSK method:
       (1)       
 
         [0000]      and  v   d   =K   d   f   D   (2)
 
         [0000]    where c is the speed of light, Δφ and Δf are the phase and frequency differences between two-step signals of FSk, f D  is the Doppler frequency and K D  is conversion constant, or using FMCW method: 
         [0000]    
       
         
           
             
               
                 
                   
                     r 
                     = 
                     
                       
                         
                           ( 
                           
                             
                               f 
                               Dup 
                             
                             + 
                             
                               f 
                               Ddown 
                             
                           
                           ) 
                         
                          
                         T 
                          
                         
                             
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         r 
                       
                       2 
                     
                   
                    
                   
                     
 
                   
                    
                   and 
                 
               
               
                 
                   ( 
                   3 
                   ) 
                 
               
             
             
               
                 
                   
                     v 
                     d 
                   
                   = 
                   
                     
                       
                         ( 
                         
                           
                             f 
                             Dup 
                           
                           - 
                           
                             f 
                             Ddown 
                           
                         
                         ) 
                       
                        
                       T 
                        
                       
                           
                       
                        
                       Δ 
                        
                       
                           
                       
                        
                       v 
                     
                     2 
                   
                 
               
               
                 
                   ( 
                   4 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where f Dup  and f Ddown  are up and down beat frequencies, T is the triangle waveform period, and Δr and Δv are range and range rate resolutions. The angle of the moving object with respect to the radar, θ, can be calculated as 
         [0000]    
       
         
           
             
               
                 
                   θ 
                   = 
                   
                     
                       sin 
                       
                         - 
                         1 
                       
                     
                      
                     
                       ( 
                       
                         
                           λ 
                           
                             2 
                              
                             
                                 
                             
                              
                             π 
                              
                             
                                 
                             
                              
                             d 
                           
                         
                          
                         Δ 
                          
                         
                             
                         
                          
                         φ 
                       
                       ) 
                     
                   
                 
               
               
                 
                   ( 
                   5 
                   ) 
                 
               
             
           
         
       
     
         [0025]    Where λ is the emitted electromagnetic wave length, d is the distance between two receiving antenna centers, Δφ is the phase difference between the two signals received at two receiving antennas. 
         [0026]      FIG. 2  shows an example of 4D continuous wave radar for a single moving object, where both the horizontal and vertical radars have one transmitter and two receivers. 
         [0027]    Each 3D radar delivers a set of 3D information. The horizontal radar generates range (r h ), range-rate (v dh ) and azimuth angle (θ), and the vertical radar yields range (r v ), range-rate (v dv ) and elevation angle (α). The range and range rate are calculated by either Equations (1) and (2) or (3) and (4). The azimuth and elevation angles are calculated by Equation (5). 
         [0028]    In  FIG. 3 , a 4D radar system  100  is shown to detect a moving object from multiple moving objects. More particularly, the system  100  of the present invention may detect positional information on a single object which may be moving in a field of moving multiple objects. The system  100  may include a vertical continuous wave radar  105  which may be positioned substantially adjacent or adjacent and perpendicular to a horizontal continuous wave radar  115 . The vertical continuous wave radar  105  may include a vertical transmitter  103  which may extend across the substantially width of the vertical continuous wave radar  105 , a first vertical receiver  107  which may extend across the top or bottom of the vertical transmitter  103  and a second vertical receiver  109  which may extend across the top or bottom of the first vertical receiver  107 . The horizontal continuous wave radar  115  may include a horizontal transmitter  113  which may extend across the substantial height of the horizontal continuous wave radar  115 , the first horizontal receiver  117  which may be adjacent to the horizontal transmitter  113  and extend across the substantial height of the horizontal transmitter  113  and the second horizontal receiver  119  which may be adjacent to the first horizontal receiver  117  and may extend across the substantial height of the horizontal transmitter  113 . 
         [0029]    The present invention includes a computer  300  to operate a signal matching algorithm to identify the signals from two radars corresponding to the same moving object using physical constraints such as matching data: for example same range and same range-rate for the same moving object over a time window. 
         [0030]      FIG. 4  presents a flow chart of the signal matching algorithm. 
         [0031]    The signal from the first horizontal receiver  117  and the signal from the second horizontal receiver  119  are used to obtain a range (equation 1) and range rate (equation 2) value from the range and range rate calculation in step  203 . More particularly a horizontal range and horizontal range rate value is calculated in step  203 . The signal from the first horizontal receiver  117  and the signal from the second horizontal receiver  119  are used to obtain an azimuth angle from the angle calculation (equation 5) in step  201  The signal from the first vertical receiver  107  and the signal from the second vertical receiver  109  are used to obtain a range (equation 1) and range rate (equation 2) value from the range and range rate calculation in step  211 . A vertical range and vertical range rate value is calculated in step  211 . The signal from the first vertical receiver and  107  and the second vertical receiver  109  are used to obtain an elevation angle from the angle calculation (equation 5) in step  213 . 
         [0032]    The range (distance from the radar to the moving object) of the horizontal radar  115  and the range of the vertical radar  105  and the range rate (velocity of the moving target assuming the radar is stationary) of the horizontal radar  115  and the vertical radar  105  are used to determine if the object detected by the horizontal radar  115  is the same object detected by the vertical radar  105 . From the step  203  and step  211 , the range of the horizontal radar  115  is compared with the range of the vertical radar  105  in step  207 . If the two ranges are the same or substantially the same, control passes to step  215 , and if the two ranges are dissimilar, control passes to step  209  indicating different objects and another object is selected to be tested. 
         [0033]    From the step  203  and step  211 , the range rate of the horizontal radar  115  is compared with the range rate of the vertical radar  105  in step  205 . If the two range rates are the same or substantially the same, control passes to step  215  indicating that the horizontal radar and the vertical radar both have identified the same object. If the range rates are different, then control passes to step  209  indicating that the horizontal radar and the vertical radar have identified different objects. Other objects are chosen for identification. 
         [0034]    The matched signals from step  205  and step  207  are combined in step  215  into 4D information of the identified object: range, range rate, azimuth angle and elevational angle. 
         [0035]    While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed.