PASSIVE RANGING BY TIME DIFFERENCE MULTI-PATH

• US 3,863,257 A
• Filed: 06/27/1972
• Issued: 01/28/1975
• Est. Priority Date: 06/27/1972
• Status: Expired due to Term

• Current Assignee: Allan E. Berry, George S. Kang
• Original Assignee: Allan E. Berry, George S. Kang
• Inventors: Kang, George S., Berry, Allan E.
• Primary Examiner(s): Wilbur, Maynard R.
• Assistant Examiner(s): Berger, Richard E.
• Application Number:
  US05/268,225
• Time in Patent Office: 945 Days
• Field of Search: 235/150.27 343/112R,112C,112D
• US Class Current: 342/458
• CPC Class Codes: G01S 11/02 using radio waves G01S19/00 takes precedence
• CPC Class Codes: G01S 5/0273 using multipath or indirect path propagation signals in position determination
• CPC Class Codes: G01S 5/12 by co-ordinating position lines of different shape, e.g. hyperbolic, circular, elliptical or radial

Abstract

Range from an observer to an electromagnetic emitter is determined by the geometry of ellipse in which the observer is at one focus, the emitter is at the other focus, and a reflector lies on the locus. The time difference of arrival of the direct signal from the emitter and the reflected signal is measured and used to compute the distance from the vortex behind the observer to the observer. Also the rate of change of the successive time differences of arrival is determined and this value together with the observer'"'"''"'"'s speed and the emitter bearing is used to compute the reflector'"'"''"'"'s position with respect to the observer. The reflector'"'"''"'"'s position and the vortex to observer'"'"''"'"'s position is used to compute the eccentricity of the ellipse which is in turn used together with time difference of arrival to compute the range.

Claims

1. A system for determining range by a moving observer of an electromagnetic emitter of successive signals derived from a geometric configuration that defines an ellipse where the emitter is at one focus and the observer is at the other focus, comprising:

a. a reflector;

b. means for measuring the time differences of arrival between successive direct emitter signals and reflected signals from the reflector;

c. means for determining the rate of change of time differences of arrival, said means being fed by the time difference measuring means;

d. means for detecting the distance from the observer to the vortex of the ellipse behind the observer defining one focus of the ellipse, the distance detecting means being fed by the time difference measuring means;

e. a source of observer speed;

f. means for detecting the bearing of the emitter relative to the observer;

g. means for detecting the position of the reflector with respect to the observer with the reflector lying on the ellipse, the position detecting means being fed by the source of observer speed, the bearing detecting means, and the time rate of change of differences of arrival measuring means;

h. means for computing the eccentricity of the ellipse, the eccentricity computing means being fed by the reflector position detecting means and the observer to vortex distance detecting means; and

i. means for computing the range between the observer and the emitter, the range computing means being fed by the eccentricity computing means and the time difference of arrival measurement means.

2. A method of determining range by a moving observer of an electromagnetic emitter of successive signals from a geometric configuration that defines a plurality of ellipses where the emitter is at one focus and the observer is at the other focus, comprising:

a. measuring the time difference of arrival times of direct emitter signals and emitter signals reflected from a reflector;

b. measuring the rate of change of the time differences of arrival of the successive emitter signals and reflections;

c. detecting the distance from the observer to the vortex of the ellipse behind the observer;

d. measuring the velocity of the observer;

e. detecting the bearing of the emitter relative to the observer;

f. detecting the position of the reflector with respect to the observer with the reflector lying on the ellipse, the reflector position detecting being defined by the observer speed, the emitter bearing and the rate of change of the time differences of arrival of successive direct emitter signals and reflected emitter signals;

g. computing the eccentricity of the ellipses as defined by the positiOn of the reflector and vortex to observer position; and

h. computing the range between the observer and the emitter as defined by the eccentricity of the ellipse and the difference of arrival times of the direct and reflected emitter signals.