Passive ranging system

• US 4,433,334 A
• Filed: 09/21/1982
• Issued: 02/21/1984
• Est. Priority Date: 09/21/1982
• Status: Expired due to Term

• Current Assignee: Eaton Corp. (Wisconsin) (Eaton Corporation PLC.)
• Original Assignee: Eaton Corp. (Wisconsin) (Eaton Corporation PLC.)
• Inventors: Caputi, William J. Jr.
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US06/423,427
• Time in Patent Office: 518 Days
• Field of Search: 343/112 R, 343/112 S
• US Class Current: 342/450
• CPC Class Codes: G01S 11/02 using radio waves G01S19/00 takes precedence

Abstract

Range and velocity of target vehicles are determined from the angles of arrival of strobes from the target vehicles to provide a completely passive, linear, ranging system. From inputs which include strobe angle, time of strobe and receiving vehicle cross range position, the targets vehicles ranges and velocities are determined. A visual presentation is provided to enhance detecting the target vehicle in a high density environment.

Claims

1. Apparatus for determining the location and velocity of a target from the angle of strobes emitted by the target, the time of the strobes, and the cross-range position of the sensor at the time of each strobe, comprising:

(a) a first cathode-ray tube,

(b) a second cathode-ray tube,

(c) a first Y deflection amplifier connected to the first cathode-ray tube to control the Y deflection of the first tube,

(d) a second Y deflection amplifier connected to the second cathode-ray tube to control the Y deflection of second tube,

(e) a first X deflection amplifier connected to the first cathode-ray tube to control the X deflection of the first tube,

(f) a second X deflection amplifier connected to the second tube to control the X deflection of the second tube,

(g) a store-replay unit means for accepting the following four input;

a trigger to store each strobe, the arc tangent of the strobe angle, and a function equal to a minimum display range desired multiplied by the arc tangent of the strobe angle, all added to the sensor cross range position, and the time of the strobe said store replay unit means storing and processing such inputs as delineated in paragraph (l),

(h) a trigger generator,

(i) a fast saw-tooth generator, receiving as an input the trigger from the trigger generator to initiate each saw-tooth pulse, the output saw-tooth being supplied to the X deflection amplifiers to provide a sweep of the cathode-ray tubes,

(j) a divide-by-N-counter receiving as an input the trigger from the trigger generator to produce a lower frequency trigger output at a frequency equal to the trigger generator frequency divided by N, the lower frequency trigger output being in synchronism with the trigger from the trigger generator,

(k) a slow saw-tooth generator receiving the slow trigger output of the divide-by-N-counter to initiate each saw-tooth wave,

(l) means for coupling the slow trigger output from the divide-by-N-counter to the store replay unit means to cause the store replay unit means to provide the following outputs;

a time of strobe, the slope of the strobe line (m) and the intercept of the strobe line (b), derived from the minimum display range, the cross range position and the arc tangent of the strobe angle as delineated in paragraph (g),

(m) a first multiplier receiving as inputs the output of the fast saw-tooth generator and the slope (m),

(n) a first adder receiving as inputs the output of the first multiplier and the strobe intercept (b),

(o) a second multiplier accepting as inputs the time from the store replay unit means and the output of the slow saw-tooth generator,

(p) a second adder accepting as inputs the output of the first adder and the output of the second multiplier,

(q) a third adder accepting as inputs the output of the second adder and the output of the slow saw-tooth generator, and supplying its output to the first Y-deflection amplifier for deflecting the first cathode-ray tube in the Y direction,

(r) a first subtracter accepting as its first input the output of the second adder and as its second input the output of the slow saw-tooth generator, the second input being subtracted from the first in the subtracter to produce a difference output which is supplied to the second Y-deflection amplifier for deflecting the second cathode-ray tube in the Y direction, and

(s) means for coupling the output from the fast saw-tooth generator to both the first and second X-deflection amplifiers to deflect the first and second cathode tubes in the X-direction.

2. A system for determining the location and velocity of a target by a sensor using the angle of strobes received from the target, the time of occurrence of the strobes and the cross range position of the sensor at the times of the strobes, comprising the steps of:

(a) presenting a representation of a first plane, said first plane encompassing the paths of the target and the sensor during the periods of the strobes, said first plane including all the strobes,

(b) plotting a representation of the positions of the sensor at the time of each strobe in said first plane,

(c) plotting a representation of a first series of lines in said first plane through the position of the sensor at the angle of the strobe received at each of the position of the sensor, said first series of lines being referred to as strobe lines,

(d) selecting a representation of the position of the sensor and the target at midrange and designating them as the reference positions and their time of occurrence as the reference time,

(e) erecting a representation of a second plane orthogonal to the first, said second plane including the strobe line passing through the reference position of the sensor, and said second plane being referred to as the reference plane,

(f) erecting a representation of a first series of plane through selected positions of the sensor and the corresponding strobe lines received at these positions, the selected positions including those occurring prior to as well as after the occurrance of the reference position, each of the planes in this first series being tilted towards the reference plane at angles which are proportional to the time elapsed between the time of occurrence of the sensor position through which a plane in the first series passes and the time of occurrence of the sensor positions through which the reference plane passes,

(g) generating a representation of a second series of lines which are formed by the intersections of the first series of planes with the reference plane,

(h) drawing a representation of the point of intersection of the second series of lines,

(i) generating a representation of a line orthogonal to the first plane which passed through the point of intersection of the second series of lines,

(j) measuring the position of the point through which the orthogonal line of step (i) passes in the first plane to determine the location of the target at the reference time, and

(k) measuring the length of the orthogonal line in subparagraph (i) to determine the velocity of the target at the reference time.

3. A system as described in claim 2, further comprising the steps of:

(a) expanding said first series of planes into wedges, the plane about which a wedge is formed being referred to as a central plane, the apex of a particular wedge being formed along a line passing through the selected positions of the sensors through which the particular central plane passes,

(b) illuminating each wedge with varying intensity, wherein the brightest areas is the central plane about which a particular wedge is formed, the brightness of the wedge having a gradient towards less brightness in traversing the area orthogonally away from the central plane of the particular wedge and towards the edges of that wedge,

(c) locating the brightest point at the intersection of the wedges produced from the first series of planes,

(d) generating a representation of a line orthogonal to the first plane which passes through the point of step (c), and

(e) measuring the position of the point through which the orthogonal line of step (c) passes to determine the location of the target at the reference time.