RADIO LOCATION DETECTION SYSTEM

• US 3,750,178 A
• Filed: 05/22/1959
• Issued: 07/31/1973
• Est. Priority Date: 05/22/1959
• Status: Expired due to Term

• Current Assignee: ITT Corporation (ITT, Inc.)
• Original Assignee: George D. Hulst
• Inventors: Hulst, George D.
• Primary Examiner(s): Borchelt, Benjamin A.
• Assistant Examiner(s): Berger, Richard E.
• Application Number:
  US03/815,744
• Time in Patent Office: 5,184 Days
• Field of Search: 340/206 328/189 343/112,12,103,17.1 250/17.54D 228/189
• US Class Current: 342/465
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 takes precedence

Abstract

1. In a radio location detection system for locating the geographical position of a source of discrete radio frequency signals having a plurality of spaced radio receiving stations at known geographical locations; the combination of a timing means at each said receiving station in time synchronism with the timing means of said other stations, means to receive said discrete radio frequency signals, means to detect from each said discrete received signal the envelope of said signal, means to invert and delay said detected envelope, means to combine said inverted and detected envelope of given amplitude with said detected envelope at a different amplitude to produce a first combined signal having a positive portion and a negative portion with a crossover point at the zero axis occurring a predetermined time after the arrival at said receiver of said discrete radio signal, means to derive from said detected envelope a gating pulse and means to combine said gating pulse with said first combined signal to produce a second combined signal containing all of said negative portion and part of said positive portion of said first combined signal and including said zero crossover point, means to derive from said second combined signal a marker pulse coincident with the time of said zero crossover point, means to determine with reference to said timing means the time of occurrence of said marker pulse signal, means to compare the times of occurrence of corresponding marker pulses at said receivers to derive the time differences therebetween, said time differences indicating at least two hyperbolic lines, the intersection of which provides the geographical position of said source of radio frequency signal.

Claims

1. In a radio location detection system for locating the geographical position of a source of discrete radio frequency signals having a plurality of spaced radio receiving stations at known geographical locations;

the combination of a timing means at each of said receiving station in time synchronism with the timing means of said other stations, means to receive said discrete radio frequency signals, means to detect from each said discrete received signal the envelope of said signal, means to invert and delay said detected envelope means to combine said inverted and detected envelope of given amplitude with said detected envelope at a different amplitude to produce a first combined signal having a positive portion and a negative portion with a crossover point at the zero axis occurring a predetermined time after the arrival at said receiver of said discrete radio signal, means to derive from said detected envelope a gating Pulse and means to combine said gating pulse with said first combined signal to produce a second combined signal containing all of said negative portion and part of said negative portion of said first combined signal and including said zero crossover point, means to derive from said second combined signal a marker pulse coincident with the time of said zero crossover point, means to determine with reference to said timing means the time of occurrence of said marker pulse signal, means to compare the times of occurrence of corresponding marker pulses at said receivers to derive the time difference therebetween, said time differences indicating at least two hyperbolic lines, the intersection of which provides the geographical position of said source of radio frequency signal.

2. In a radio locating detection system for locating the geographical position of a source of discrete radio signals having a plurality of spaced radio receiving stations at known geopraphical locations;

the combination of a timing means at each said receiving station in time synchronism with the timing means of said other stations, means to receive said discrete radio frequency signals, means to detect from each said discrete received signal the envelope of said signal, means to invert and delay said detected envelope, means to combine said inverted and detected envelope of given amplitude with said detected envelope at a different amplitude to produce a first combined signal having a positive portion and a negative portion with a crossover point at the zero axis occurring a predetermined time after the arrival of said discrete radio signals, means to derive from said detected envelope a gating pulse, means to combine said gating pulse with said first combined signal to produce a second combined signal containing all of said negative portion and a part of said positive portion and including said zero crossover point, means to pass only said positive portion including said zero crossover point, means to invert and clip said positive portion to form a square wave, means to differentiate said square wave to form negative and positive pulse signals, said negative pulse occurring at the time of said zero crossover point, means to determine with reference to said timing means the time of the occurrence of said negative pulse signal, means to compare the times of occurrence of corresponding negative pulses at said receivers to derive the time differences therebetween, said time differences indicating at least two hyperbolic lines, the intersection of which provides the geographical position of said source of radio frequency signals.

3. A radio location detection system according to claim 2 wherein said means to determine the time of occurrence of said negative pulse signal comprises a digital clock controlled by said timing means and producing a pulse output, a plurality of AND gates, means coupling the said clock pulse output and said negative pulse to each of said AND gates whereby the coincidence of occurrence of said clock pulse and said negative pulse at any of said AND gates will cause a digital output from said AND gate indicative of the time of occurrence of said negative pulse and means to store said digital output from said AND gate.

4. A radio location detection system according to claim 3 wherein said comparing means include a computer, means to transmit said digital information from each of said station indicative of said time of occurrence of said negative pulse at each said station to said computer whereby said computer subtracts said occurrence times to derive the time differences therebetween, said time differences being indicative of the time differences in the arrival of said discrete signal at each said receiving station.

5. In a radio location direction system for locating the geographical position of a source of discrete radio frequency signals having a plurality of spaced receiving stations at known geographical locations;

the combination of a timing means at each said receiving sTation in time synchronism with the timing means of said other stations, means to receive said discrete radio frequency signals, means to detect from each said discrete received signal the envelope of said signal, means to invert and delay said detected envelope, means to combine said inverted and detected envelope of full amplitude with said detected envelope of half amplitude to produce a combined signal having a positive portion and a negative portion with a crossover point at the zero axis occuring a predetermined time after the arrival at said receiver of said discrete radio signal, means to derive from said combined signal a marker pulse coincident with the time of said zero crossover point, a digital clock controlled by said timing means and producing a pulse output, a plurality of AND gates, means coupling said clock pulse output and said marker pulse to each of said published gates whereby the coincidence of occurrence of said clock pulse and said negative pulse at any of said AND gates will cause a digital output from said AND gate indicative of the time of occurrence of said marker pulse, a register, means to couple said outputs of said AND gates to said register for adding the times of occurrence of said marker pulses derived from said discrete radio frequency signals during a predetermined time period and deriving from said added occurrence times the average time of occurrence of said marker pulses, a computer, means coupling the output of said register at each said receiving station to said computer whereby said computer subtracts said averaged occurrence times to derive the time difference therebetween, said time differences being indicative of the time differences in the arrival of said radio frequency signals at each said receiving station, said time differences indicating at least two hyperbolic lines, the intersection of which provides the geographical position of said source of radio frequency signals.

6. A system for deriving a timemarker pulse from a received discrete radio frequency signal at a predetermined time after the arrival of said signal comprising means to receive said signal, means to detect the envelope of said discrete signal, means to invert and delay said detected envelope, means to combine said inverted and delayed envelope of given amplitude and said detected envelope at a different amplitude to produce a first combined signal having a negative portion and a positive portion with a crossover point at the zero axis occurring a predetermined time after arrival of said discrete radio signal, and means to develop therefrom a marker pulse occurring at the time of said zero crossover point thus marking a predetermined time interval after the arrival of said discrete radio frequency signal.

7. A system for deriving a marker pulse according to claim 6 wherein said means to derive said marker pulse from said first combined signal comprise means to derive from said detected envelope a gating pulse, means to combine said gating pulse with said first combined signal to produce a second combined signal containing said negative portion and a part of said positive portion and including said zero crossover point, means to pass only said positive portion including said zero crossover point, means to invert and clip said positive portion to form a square wave, means to differentiate said square wave to form negative and positive pulse signals, said negative pulse occurring at said zero crossover point and constituting said marker pulse.

8. In a radio location detection system for locating the geographical position of a source of discrete radio frequency signals having a plurality of spaced radio receiving stations at known geographical locations, the combination of a timing means at each of said receiving stations in time synchronism with the timing means of said other stations, means to derive a marker pulse from each said discrete signal, a digital clock controlled by said timing means and producing a pulse output, a plurality of AND gates, means coupling said clock pulse output and said marker pulse to each of said AND gates whereby the coincidence of said clock pulse and said marker pulse at any of said AND gates will cause a digital ouptut from said AND gate indicative of the time of occurrence of said marker pulse and means to compare the times of occurrence of corresponding marker pulses of said receivers to derive the time difference therebetween, said time differences indicating at least two hyperbolic lines, the intersection of which provides the geographical position of said source of radio frequency signals.

9. In a radio location system according to claim 8 wherein said comparing means include a include means to transmit said digital information from each said station indicative of the time of occurrence of said marker pulse at each said station to said computer whereby said computer subtracts said occurence times to derive the time difference therebetween, said time differences being indicative of the time differences in the arrival of said discrete signal at each said receiving station.

10. In a radio location detecting system for locating the geographical position of a source of discrete radio frequency signals having a plurality of spaced radio receiving stations at known geographical locations;

the combination of a timing means at each said receiving station in time synchronism with the timing means of said other stations, means to derive at each receiving station a marker pulse from each said discrete signal, said means to derive said marker pulse comprising means to detect the envelope of said discrete radio frequency signal, means to amplify, invert and delay said detected envelope, and means to combine said inverted and delayed envelope of given amplitude and said detected envelope at a different amplitude to produce a combined signal having a negative portion and a positive portion with a crossover point at the zero axis, said zero crossover point determining the timing of said marker pulse, means to determine with reference to said timing means the time occurrence of said marker pulse, means to compare the times of occurrence of corresponding marker pulses of said receivers to derive the time difference therebetween, said time differences indicating at least two hyperbolic lines, the intersection of which provides the geographical position of said source of radio frequency signals.

11. In a radio location detection system for locating the geographical position of a source of discrete radio frequency signals having a plurality of spaced radio receiving stations at known geographical locations;

the combination of a timing means at each said receiving station in time synchronism with the timing means of said other station, means to receive said discrete radio frequency signals, means to detect from each said discrete received signal the envelope of said signal, means to invert and delay said detected envelope, means to combine said inverted and detected envelope of given amplitude with said detected envelope at a different amplitude to produce a first combined signal having a positive portion and a negative portion with a crossover point at the zero axis occurring a predetermined time after the arrival at said receiver of said discrete radio signal, the amplitude of said inverted and delayed envelope being greater than the amplitude of said detected envelope, means to derive from said detected envelope a gating pulse and means to combine said gating pulse with said first combined signal to produce a second combined signal containing all of said negative portion and part of said positive portion of said first combined signal and including said zero crossover point, means to derive from said second combined signal a marker pulse coincident with the time of said zero crossover point, means to determine with reference to said timing means the time of occurrence of said marker pulse signal, means to compare the times of occurrence of corresponding marker pulses at said receivers to derive the time differences therebetween, said time differences indicating at least two hyperbolic lines, the intersection of which provides the geographical position of said source of radio frequency signal.

12. In a radio location detection system according to claim 11 wherein the ratio of the amplitude of said inverted and delayed envelope to the amplitude of said detected envelope is substantially two-to-one.