System for sensing aircraft and other objects

• US 8,373,591 B2
• Filed: 10/22/2010
• Issued: 02/12/2013
• Est. Priority Date: 10/30/2009
• Status: Active Grant

• Current Assignee: Jed Margolin
• Original Assignee: Jed Margolin
• Inventors: Margolin, Jed
• Primary Examiner(s): Sotomayor, John B
• Assistant Examiner(s): Barker, Matthew M
• Application Number:
  US12/910,779
• Publication Number:
  US 20110169684A1
• Time in Patent Office: 844 Days
• Field of Search: 342/147
• US Class Current: 342/146
• CPC Class Codes: G01S 11/02 using radio waves G01S19/00 takes precedence
• CPC Class Codes: G01S 13/003 Bistatic radar systems; Multistatic radar systems
• CPC Class Codes: G01S 13/933 of aircraft or spacecraft
• CPC Class Codes: G01S 5/12 by co-ordinating position lines of different shape, e.g. hyperbolic, circular, elliptical or radial

Abstract

A system for sensing aircraft and other objects uses bistatic radar with spread-spectrum signals transmitted from remotely located sources such as aircraft flying at very high altitudes or from a satellite constellation. A bistatic spread spectrum radar system using a satellite constellation can be integrated with a communications system and/or with a system using long baseline radar interferometry to validate the digital terrain elevation database. The reliability and safety of TCAS and ADS-B are improved by using the signals transmitted from a TCAS or ADS-B unit as a radar transmitter with a receiver used to receive reflections. Aircraft and other objects using spread spectrum radar are detected by using two separate receiving systems. Cross-Correlation between the outputs of the two receiving systems reveals whether a noise signal is produced by the receiving systems themselves or is coming from the outside.

Claims

1. A system for sensing aircraft and other objects comprising:

(a) four or more orbiting satellites;

(b) an antenna;

(c) a receiver;

(d) a data buffer;

(e) a cross-correlator with two or more inputs and one or more outputs;

(f) a system controller;

(g) a list of code keys;

(h) a display;

wherein

(a) each of said four or more orbiting satellites is configured to transmit a signal encoded by a unique code key selected from said list of code keys,

(b) said antenna is connected to said receiver,

(c) the output of said receiver is connected to the input of said data buffer,

(d) the output of said data buffer is connected to a first of said two or more inputs of said cross-correlator,

(e) said system controller is configured to provide a second of said two or more inputs of said cross-correlator,

(f) said system controller is configured to receive an output of said one or more outputs of said cross-correleator,

and whereby

(a) said system controller is configured to use said signal transmitted by each of said four or more orbiting satellites, said list of code keys, and said cross-correlator to uniquely identify each of said four or more orbiting satellites,

(b) said system controller is configured to determine a distance and a direction to each uniquely identified satellite,

(c) said signal from said each uniquely identified satellite is reflected by a target producing a uniquely identifiable reflected signal,

(d) each said uniquely identifiable reflected signal is received by said antenna, which is connected to said receiver, which is connected to said data buffer, which is connected to said first of said two or more inputs of said cross-correlator,

(e) said system controller is configured to use said list of code keys and said cross-correlator to identify each said uniquely identifiable reflected signal,

(f) said system controller is configured to use each said uniquely identifiable reflected signal and said range and said direction to said each uniquely identified satellite to determine a range and a bearing to said target, and

(g) said system controller is configured to display said range and said bearing on said display,

and wherein

(a) the range and direction to a first of said four or more orbiting satellites and the signal from said first of said four or more orbiting satellites reflected from said target produce a first ellipsoid with said first of said four or more orbiting satellites at one focal point of said first ellipsoid, said antenna at the other focal point of said first ellipsoid, and said target on the surface of said first ellipsoid,

(b) the range and direction to a second of said four or more orbiting satellites and the signal from said second of said four or more orbiting satellites reflected from said target produce a second ellipsoid with said second of said four or more orbiting satellites at one focal point of said second ellipsoid, said antenna at the other focal point of said second ellipsoid, and said target on the surface of said second ellipsoid,

(c) the range and direction to a third of said four or more orbiting satellites and the signal from said third of said four or more orbiting satellites reflected from said target produce a third ellipsoid with said third of said four or more orbiting satellites at one focal point of said third ellipsoid, said antenna at the other focal point of said third ellipsoid, and said target on the surface of said third ellipsoid,

(d) the range and direction to a fourth of said four or more orbiting satellites and the signal from said fourth of said four or more orbiting satellites reflected from said target produce a fourth ellipsoid with said fourth of said four or more orbiting satellites at one focal point of said fourth ellipsoid, said antenna at the other focal point of said fourth ellipsoid, and said target on the surface of said fourth ellipsoid,

(e) said first ellipsoid and said second ellipsoid intersect in an ellipse with said target located on said ellipse,

(f) said third ellipsoid and said ellipse intersect at two points with said target located at one of said two points,

(g) said fourth ellipsoid intersects with only one of said two points with said target located at said only one of said two points.

2. The system of claim 1 further comprising communications links between each of said four or more orbiting satellites.

3. The system of claim 2 further comprising a satellite receiver in at least two or more of said four or more orbiting satellites whereby a signal transmitted by said at least two or more of said four or more orbiting satellites and said satellite receiver are configured to perform long baseline radar interferometric measurements of terrain elevations.

4. The system of claim 1 wherein at least one of said four or more orbiting satellites is located in low earth orbit.

5. The system of claim 1 further comprising:

(a) a receiver in each of said four or more orbiting satellites;

(b) a transmitter;

whereby said receiver in each of said four or more orbiting satellites and said transmitter are configured for said transmitter to send transmissions to at least one of said four or more orbiting satellites in order to provide two-way communications through said at least one of said four or more orbiting satellites.

6. A system for sensing aircraft and other objects comprising:

(a) one or more orbiting satellites;

(b) a first antenna;

(c) a second antenna;

(d) a controller for said second antenna;

(e) an antenna multiplexer;

(f) a receiver;

(g) a data buffer;

(h) a cross-correlator with two or more inputs and one or more outputs;

(i) a system controller;

(j) a list of code keys;

(k) a display;

wherein

(a) said antenna multiplexer is configured to select between said first antenna and said second antenna under control of said system controller,

(b) the output of said antenna multiplexer is connected to the input of said receiver,

(c) said second antenna is directional and is controlled by said antenna controller under control of said system controller,

(d) the output of said receiver is connected to the input of said data buffer,

(e) the output of said data buffer is connected to a first of said two or more inputs of said cross-correlator,

(f) said system controller is configured to provide a second of said two or more inputs of said cross-correlator,

(g) said system controller is configured to receive an output of said one or more outputs of said cross-correleator,

and whereby

(a) said first antenna is selected by said system controller,

(b) said one or more orbiting satellites is configured to transmit a signal encoded by a unique code key selected from said list of code keys,

(c) said system controller is configured to use said signal transmitted by said one or more orbiting satellites, said list of code keys, and said cross-correlator to uniquely identify said one or more orbiting satellites,

(d) said system controller is configured to determine a distance to a uniquely identified satellite,

(e) said signal from said uniquely identified satellite is reflected by a target producing a uniquely identifiable reflected signal,

(f) said uniquely identifiable reflected signal is received by said second antenna, which is connected to said receiver, which is connected to said data buffer, which is connected to said first of said two or more inputs of said cross-correlator,

(g) said system controller is configured to use said list of code keys and said cross-correlator to identify said uniquely identifiable reflected signal,

(h) said system controller is configured to use said antenna controller to direct said second antenna at the source of said uniquely identifiable reflected signal to produce a bearing to said uniquely identifiable reflected signal,

(i) said system controller is configured to use said uniquely identifiable reflected signal and said range to said uniquely identified satellite to determine a range and a bearing to said target, and

(j) said system controller is configured to display said range and said bearing on said display,

and wherein

(a) the range and direction to said one or more orbiting satellites and the signal from said one or more orbiting satellites reflected from said target produces an ellipsoid with said one or more orbiting satellites at one focal point of said ellipsoid, said antenna at the other focal point of said ellipsoid, and said target on the surface of said ellipsoid,

(b) said second antenna is aimed to receive said signal from said one or more orbiting satellites reflected from said target, and

(c) the direction of said second antenna is used to determine the location of said target on said ellipsoid.

7. A system for sensing aircraft and other objects during daytime comprising:

(a) a first directional antenna;

(b) a first antenna controller;

(c) a first receiver;

(d) a first data buffer;

(e) a second directional antenna;

(f) a second antenna controller;

(g) a second receiver;

(h) a second data buffer;

(i) a cross-correlator;

(j) a system controller;

(k) a display;

whereby

(a) the position of said first directional antenna is controlled by said first antenna controller under the control of said system controller,

(b) the position of said second directional antenna is controlled by said second antenna controller under the control of said system controller,

(c) said cross-correlator has two inputs and one output,

(d) said first directional antenna is connected to the input of said first receiver,

(e) the output of said first receiver is connected to the input of said first data buffer,

(f) the output of said first data buffer is connected to a first input of said cross-correlator under control of said system controller,

(g) said second directional antenna is connected to the input of said second receiver,

(h) the output of said second receiver is connected to the input of said second data buffer,

(i) the output of said second data buffer is connected to a second input of said cross-correlator under control of said system controller,

(j) said system controller is configured to direct said first antenna controller to point said first directional antenna at the Sun to produce a first signal,

(k) said system controller is configured to direct said cross-correlator to perform a cross-correlation between said first signal received from said first directional antenna which is stored in said first data buffer and a second signal received from said second directional antenna which is stored in said second data buffer,

(l) said system controller is configured to direct said second antenna controller to point said second directional antenna to produce said second signal to maximize said output of said cross-correlator where said second directional antenna is not pointed at said Sun,

whereas

(a) said second signal is a reflection of said first signal produced by said Sun, said reflection being produced by a target,

(b) a time delay between said first signal and said second signal is used to determine an ellipsoid with said first directional antenna located at one focal point of said ellipsoid, said Sun located at the other focal point of said ellipsoid and said target on the surface of said ellipsoid,

(c) the direction of said second directional antenna is used to determine the location of said target on said ellipsoid,

(d) said system controller is configured to use said location of said target on said ellipsoid to produce a range and a bearing to said target, and

(e) said system controller is configured to display said range and said bearing on said display.