Method for reducing angular blur in radar pictures

• US 7,236,125 B2
• Filed: 01/25/2005
• Issued: 06/26/2007
• Est. Priority Date: 01/27/2004
• Status: Active Grant

• Current Assignee: Saab AB
• Original Assignee: Saab AB
• Inventors: Tullsson, Bert-Eric
• Primary Examiner(s): Gregory; Bernarr E.
• Application Number:
  US11/041,244
• Publication Number:
  US 20060066475A1
• Time in Patent Office: 882 Days
• Field of Search: 342 25 R- 25 F, 342/89, 342 94- 97, 342/118, 342128-147, 342159-176, 342/179, 342189-197, 342149-154
• US Class Current: 342/173
• CPC Class Codes: G01S 13/426 Scanning radar, e.g. 3D radar G01S13/66 takes precedence
• CPC Class Codes: G01S 7/4026 Antenna boresight
• CPC Class Codes: G01S 7/403 in azimuth, i.e. in the horizontal plane
• CPC Class Codes: G01S 7/4034 in elevation, i.e. in the vertical plane

Abstract

A method for reducing angular blur in radar pictures achieved in range bin based detection systems includes measuring a variable S(x, y) such as amplitude or power as a function of an angle x and a distance y. An expression:
corrected angular position=angular position+angle correction
is determined in each range bin for a plurality of angular values x. The term “angle correction” includes derivative(s) of first or higher order of the variable S(x). The variable measured at the angular position “angular position” is moved to the variable in the angular position “corrected angular position”, and the moved variable and the variable in “corrected angular position” are processed by adding or maximizing the values.

Claims

1. A method useful for reducing angular ambiguity in a radar detection system having a plurality of range bins, the method comprising:

measuring a power variable S(x, y) as a function of an angle x and a distance y;

determining, for each of a plurality of angular values x and for a given distance y, a corrected angular position as a sum of an angular position and an angle correction for each range bin of the plurality of range bins; and

adding an amount of measured power at said angular position to an amount of measured power at the corrected angular position,

wherein said angle correction comprises a ratio S′

(x)/S(x) and wherein said S′

(x) is a partial derivative in an angular direction of the measured variable S(x).

2. The method of claim 1, wherein the partial derivative is numerically estimated using measured values of S(x).

3. The method of claim 1, wherein the partial derivative is estimated using finite differences of Δ

S/Δ

x.

4. The method of claim 1, wherein the partial derivative is estimated using either averaged or low-pass filtered finite differences.

5. The method of claim 1, wherein measured information from the variable S(x) are only used for such values of x in which the variable S(x) exceeds a threshold value.

6. The method of claim 1, wherein the angle correction comprises a quotient q=S′

(x)/(S(x)+t), wherein S′

(x) is a first derivative of the measured variable S(x) and t is a positive threshold.

7. The method of claim 1, wherein said measured variable S(x) only assumes discrete values and is represented by a variable S(i, j) with i1≦

i2 and j1≦

j ≦

j2.