NAVIGATION SYSTEM USING SATELLITES AND PASSIVE RANGING TECHNIQUES

• US 3,789,409 A
• Filed: 10/08/1970
• Issued: 01/29/1974
• Est. Priority Date: 10/08/1970
• Status: Expired due to Term

• Current Assignee: Roger L. Easton
• Original Assignee: Roger L. Easton
• Inventors: Easton, Roger L.
• Primary Examiner(s): Farley, Richard A.
• Assistant Examiner(s): Berger, Richard E.
• Application Number:
  US05/079,307
• Time in Patent Office: 1,209 Days
• Field of Search: 343/112D,112R,1ST
• US Class Current: 342/357.21
• CPC Class Codes: G01S 11/08 using synchronised clocks

Abstract

A navigation system wherein the navigator'"'"''"'"'s location is obtained by determining the navigator'"'"''"'"'s distance (or range) from one or more satellites of known location. Each satellite transmits multifrequency signals that are derived from a stable oscillator which is phase synchronized with the navigator'"'"''"'"'s equipment that produces similar multifrequency signals. Phase comparison between the signals received from the satellites and the locally produced signals indicates both the distance between the navigator and the satellites and the navigator'"'"''"'"'s location. In determining his location, the presence of the navigator is not revealed since no interrogatory transmission by him is required.

Claims

1. A navigation system comprising:

at least two earth satellites, the instantaneous locations of which are precisely known, each satellite including transmitting means for broadcasting multifrequency signals derived from a first extremely stable oscillator, and a navigator'"'"''"'"'s station including;

receiving means for receiving said broadcast multifrequency signals;

signal generating means including a second extremely stable oscillator for producing multifrequency signals the same as said broadcast signals, and phase comparison means connected to said receiving means and to said signal generating means for comparing the phase of said received multifrequency signals to the phase of said produced multifrequency signals whereby the location of said navigator'"'"''"'"'s station can be determined from the intersection of lines of position established by detecting the station'"'"''"'"'s distance from the instantaneously known location of the satellites derived from said phase comparisons without the necessity of betraying the presence of said navigator'"'"''"'"'s station by an interrogation signal.

2. The technique of determining a navigator'"'"''"'"'s location by determining his position relative to a moving satellite whose location is known at all times comprising the steps of:

measuring the phase difference between multifrequency signals received from said satellite at first and second locations and reference signals of corresponding frequencies produced at said navigator'"'"''"'"'s location, said signals including a low frequency signal and a signal having a frequency at least one hundred times higher than the low frequency signal;

determining approximate first and second distances between said navigator and said satellite at the first and second locations, respectively, from the phase comparison of said low frequency signals;

determining accurate first and second distances from said approximate distances and the phase comparison of the higher frequency signals;

establishing first and second lines of position of said navigator from said accurately determined distances, whereby said navigator'"'"''"'"'s location is determined by the intersection of said first and second lines of position.

3. The navigation system of claim 1 wherein no more than one satellite broadcasts at any one carrier frequency.

4. The navigation system of claim 3 wherein said receiving means functions to separate said multifrequency signals from the carrier frequency which is broadcast.

5. The navigation system of claim 4 wherein said signal generating means includes count down circuits which are connected to said second stable oscillator.

6. The navigation system of claim 5 wherein said transmitting Means includes multiplier and synthesizer means which are connected to said first stable oscillator and which produce said carrier frequency signal.