Patent ID: 11906646
Assignee: SOUTHEAST UNIVERSITY
Field: Measurement (Instruments)
Classification: CPC G  Y | IPC G

Claim 0:
1. A method for estimating the air propagation delay of a direct wave, comprising
1) obtaining a received signal through a radio wave receiving device, and estimating an azimuth of arrival, an elevation angle and a total delay of each path of a multipath wave arriving at a receiving end; the estimated azimuth of arrival, elevation angle and total delay of each path of the multipath wave arriving at the receiving end comprise the azimuth of arrival, elevation angle of arrival, and total delay of arrival (φr,0, θr,0, τr,0) of the direct wave, and the azimuth of arrival, elevation angle of arrival, and total delay of arrival (φr,1, θr,1, τr,1) of a reflected wave;
2) obtaining a departure angle of the reflected wave according to the geometric principle of wave reflection and an arrival angle of the reflected wave measured by the radio wave receiving device; the arrival angle of the reflected wave refers to the azimuth of arrival and the elevation angle of arrival of the reflected wave, and the departure angle of the reflected wave refers to the azimuth of departure and the elevation angle of departure of the reflected wave;
3) selecting a hypothetical point on a ray where the arrival angle of the direct wave is located as a transmitting end, and calculating the air propagation delay of the direct wave and the position of a reflection point of the reflected wave at the hypothetical point; the position of the reflection point is determined by the midpoint of a common perpendicular line segment between the ray of the departure angle of the reflected wave and the ray of the arrival angle;
4) calculating a propagation distance of the reflected wave according to the total delay of the direct wave, the total delay of the reflected wave and the position of the selected hypothetical point;

lsc=|rr−rsc+|rsc−rp|

wherein, lsc means the propagation distance of the reflected wave, rr means the coordinate of the receiving end, rsc means the estimated coordinate of the reflection point of the reflected wave, rp means the coordinate of the hypothetical point, and |⋅| means a modulus value;
5) calculating the sum of the distance between the hypothetical point of the transmitting end and the reflection point and the distance between the reflection point and the receiving end, making a difference between the sum and the propagation distance of the reflected wave, and taking an absolute value; selecting the hypothetical point with the smallest absolute value as the position of the transmitting end; calculating the distance between the transmitting end and the receiving end and dividing the distance by the propagation velocity of the radio wave to obtain the estimated value of the air propagation delay of the direct wave;, the path propagation delay when the reflected wave reaches the receiving end is:

τp,1=τr,1−τr,0+τp,0 

wherein, τp,1 means the path propagation delay when the reflected wave reaches the receiving end, τr,1 means the measured total delay of the reflected wave, τr,0 means the measured total delay of the direct wave, and τp,0 means the direct path propagation delay from the hypothetical point P of the transmitting end to the receiving end;
the path propagation distance of the reflected wave reaching the receiving end is l′sc=cτp,1, where c is the propagation velocity of an electromagnetic wave in space;
choose an appropriate P point position to obtain the smallest cost function:

ƒ(rp)=|lsc−l′sc|

wherein, ƒ(rp) means the cost function, lsc means the propagation distance of the reflected wave calculated according to the spatial position coordinate, and l′sc means the propagation distance of the reflected wave calculated according to the calculated path propagation delay when the reflected wave reaches the receiving end;
an estimated value {circumflex over (τ)} of the propagation delay of the direct wave is:, τ
   ^
  
  =
  
   
    arg
      
    
     min
     
      r
      p
     
    
    
     f
     ⁡
     (
     
      r
      p
     
     )
    
   
   =
   
    arg
    ⁢
    
     
        
      min
     
     τ
    
    ⁢
    
     f
     ⁡
     (
     
      c
      ⁢
      τ
     
     )
    
   
  
 

wherein, {circumflex over (τ)} means the estimated value of the propagation delay of the direct wave, rp means the distance from a hypothetical transmitting point to the receiving end, and τ means the propagation delay of the direct wave.