ANGULAR POSITION DETERMINING SYSTEM COMPENSATED FOR DOPPLER

• US 3,704,465 A
• Filed: 08/28/1970
• Issued: 11/28/1972
• Est. Priority Date: 08/28/1970
• Status: Expired due to Term

• Current Assignee: Herbert F. Baurle, Raymond J. Masak
• Original Assignee: Herbert F. Baurle, Raymond J. Masak
• Inventors: Masak, Raymond J., Baurle, Herbert F.
• Primary Examiner(s): Borchelt, Benjamin A.
• Assistant Examiner(s): Berger, Richard E.
• Application Number:
  US05/067,820
• Time in Patent Office: 823 Days
• Field of Search: 343/1SA,16D,113DE,102,18M,16R 325/65
• US Class Current: 342/386
• CPC Class Codes: G01S 1/40 the apparent movement of the antenna being produced by cyclic sequential energisation of fixed antennas
• CPC Class Codes: G01S 11/10 using Doppler effect

Abstract

Disclosed are systems for determining the true angular position of a target with respect to a reference location. One such system employs a novel array of antenna units at the reference location. The units are uniquely excited by a pulse type signal in two opposite predetermined sequences to produce a pair of radiated pulse trains. A target located in the field of this array is illuminated by these radiated pulse trains each of which has a phase distribution proportional to the angular position of the target with respect to the array and opposite in sense to that of the other. Furthermore, the frequency of each pulse train undergoes a doppler shift due to the radial velocity, if any, of the target with respect to the array and therefore the ambiguity due to such shifts can be compensated for by detecting the phase distribution of each pulse train and processing the information obtained. In this manner an indication of the target'"'"''"'"'s true angular position, free from doppler ambiguities, can be provided either at the reference location alone, the target alone, or at both the reference location and the target.

Claims

1. A system for determining the true angular position of a target with respect to a reference location which system compensates for doppler ambiguities due to the relative motion of the target with respect to the reference location, comprising;

an array of antenna units at said reference location;

means for supplying a first pulse type signal to selected units of said array in a first predetermined sequence and with a first selected phase relationship to cause a first corresponding pulse type signal to be radiated from each unit during a time interval unique to that unit;

means for supplying a second pulse type signal to selected units of said array in a second predetermined sequence, opposite in order of units to said first predetermined sequence, and with a second selected phase relationship to cause a second corresponding pulse type signal to be radiated from each unit during a time interval unique to that unit, whereby a target located in the field of said array is illuminated by a pair of pulse trains each having a phase distribution opposite in sense to that of the other and proportional to the angular position of said target with respect to said array and each having a doppler component approximately equal to the doppler component of the other;

means for receiving the pair of pulse trains which have illuminated the target; and

means for detecting the phase distribution and doppler component of each of said received pulse trains and for providing a pair of output indications, each representative of one of said detected phase distributions and doppler components, whereby the true angular position of said target with respect to said array and therefore with respect to said reference location is represented by the relationship between said pair of indications.

2. A system in accordance with claim 1 wherein said angular position determining system further comprises means for processing said pair of output indications to provide a final output indication representative of said true angular position, compensated for the ambiguity in angular position due to said doppler components and substantially free from the effects of multipath.

3. A system in accordance with claim 2 wherein said receiving, detecting, and processing means are located at said reference location and wherein said target includes means for retransmitting said pair of radiated pulse trains to said reference location thereby providing said output indication at said reference location.

4. A system in accordance with claim 2 wherein said receiving, detecting, and processing means are located at said reference location and wherein said pair of radiated pulse trains are reflected by said target to said reference location thereby providing said output indication at said reference location.

5. A system in accordance with claim 2 wherein said receiving, detecting, and processing means are located at said target, thereby providing said target with an indication of its angular position with respect to said reference location.

6. An aircraft landing system which determines the true angular position of an aircraft with respect to a reference location which system compensates for doppler ambiguities due to the relative motion of the aircraft with respect to the reference location comprising:

an array of antenna units at said reference location;

means for supplying a first pulse type signal to a first unit of said array;

delay means for coupling said first pulse type signal to selected remaining units of said array in a first predetermined sequence and with a first predetermined phase relationship to cause a first corresponding pulse type signal to be raDiated from each unit during a time interval unique to that unit;

means for supplying a second pulse type signal to a second unit of said array;

delay means for coupling said second pulse type signal to selected remaining units of said array in a second predetermined sequence, opposite in order of units to said first predetermined sequence, and with a second selected phase relationship to cause a second corresponding pulse type signal to be radiated from each unit during a time interval unique to that unit, whereby an aircraft located in the field of said array is illuminated by a pair of first and second pulse trains each having a phase distribution opposite in sense to that of the other and proportional to the angular position of said aircraft with respect to said array and each having a doppler component approximately equal to the doppler component of the other;

means for receiving the pair of first and second pulse trains which have illuminated the target;

means for detecting the phase distribution and doppler component of said received first and second pulse trains, by forming a pair of first and second electrical signals each having a waveshape substantially equivalent to the field intensity characteristic which would be formed at said aircraft by a predetermined scanning beam illuminating said aircraft, and for providing a pair of output indications each representative of the phase distribution and doppler component of a corresponding one of said pulse trains; and

means for processing said output indications to provide a final output indication representative of the true angular position of said aircraft with respect to said array and therefore with respect to said reference location, compensated for the ambiguities in position due to said doppler components and substantially free from the effects of multipath.

7. Apparatus usable in a system for determinig the true angular position of a target with respect to a reference location comprising:

an array of antenna units at said reference location;

means for supplying a first pulse type signal to selected units of said array in a first predetermined sequence and with a first selected phase relationship to cause a first corresponding pulse type signal to be radiated from each unit during a time interval unique to that unit; and

means for supplying a second pulse type signal to selected units of said array in a second predetermined sequence, opposite in order of units to said first predetermined sequence, and with a second selected phase relationship to cause a second corresponding pulse type signal to be radiated from each unit during a time interval unique to that unit, whereby a target located in the field of said array is illuminated by a pair of pulse trains each having a phase distribution opposite in sense to that of the other and proportional to the angular position of said target with respect to said array and each having a doppler component approximately equal to the doppler component of the other.

8. Apparatus usable in a system for determining the true angular position of a target with respect to a reference location comprising:

an array of antenna units at said reference location;

means for supplying a first pulse type signal to a first unit of said array;

delay means for coupling said first pulse type signal to selected remaining units of said array in a first predetermined sequence and having a first predetermined phase relationship to cause a first pulse type signal to be radiated from each unit during a time interval unique to that unit;

means for supplying a second pulse type signal to a second unit of said array; and

delay means for coupling said second pulse type signal to selected remaining units of said array in a second predetermined sequence, opposite in order of units to said first predetermined sequence, and with a second selected phase relationship to cause a second corresponding pulse type signal to be radiated from each unit during a time interval unique to that unit, whereby a target located in the field of said array is illuminated by a pair of pulse trains each having a phase distribution opposite in sense to that of the other and proportional to the angular position of said target in relation to said array and each having a doppler component approximately equal to the doppler component of the other.

9. Apparatus usable in a system for determing the true angular position of a target with respect to a reference location which system compensates for doppler ambiguities due to the relative motion of the target with respect to the reference location, wherein said target is illuminated with a pair of pulse trains each having a phase distribution opposite in sense to that of the other and proportional to the angular position of said target with respect to said reference location and each having a doppler component approximately equal to the doppler component of the other comprising:

means for receiving the pair of pulse trains which have illuminated the target; and

means for detecting the phase distribution and doppler component of each of said received pulse trains and for providing a pair of output indications, each representative of one of said detected phase distributions and doppler components, whereby the true angular position of said target with respect to said array and therefore with respect to said reference location is represented by the relationship between said pair of indications.

10. Apparatus in accordance with claim 9 wherein said angular position determining system further comprises means for processing said pair of output indications to provide a final output indication representative of said true angular position, compensated for the ambiguity in angular position due to said doppler components and substantially free from the effects of multipath.

11. Apparatus usable in a system for determining the true angular position of a target with respect to a reference location which system compensates for doppler ambiguities due to the relative motion of the target with respect to the reference location, wherein said target is illuminated with a pair of first and second pulse trains each having a phase distribution opposite in sense to that of the other and proportional to the angular position of said target with respect to said reference location and each having a doppler component approximately equal to the doppler component of the other, comprising:

means for receiving the pair of first and second pulse trains which have illuminated the target;

means for detecting the phase distribution and doppler component of said received first and second pulse trains, by forming a pair of first and second electrical signals each having a waveshape substantially equivalent to the field intensity characteristic which would be formed at said target by a predetermined scanning beam illuminating said target, and for providing a pair of output indications each representative of the phase distribution and doppler component of a corresponding one of said pulse trains; and

means for processing said output indications to provide a final output indication representative of the true angular position of said target with respect to said array and therefore with respect to said reference location and compensated for the ambiguity in angular position due to said doppler components.

12. Apparatus in accordance with claim 11 wherein said detecting means comprises a plurality of matched filters, each matched to the phase distribution due to a selected angular position, and together providing said first and second electrical signals from the particular filters matched to the phase distribution which correspond to said first and second received pulse trains.

13. Apparatus in accordance with claim 11 wherein said detecting means comprises a pair of Fourier transformers, each for detecting the phase distribution and doppler component of one of said pulse trains and each for developing an output indication in real time which is representative of said phase distribution and doppler component.

14. Apparatus in accordance with claim 11 wherein said detecting means comprises means including a pair of frequency lock loops for combining the pulses of said received pulse trains to form said pair of electrical signals, each signal having a center frequency representative of the phase distribution and doppler component of one of said pulse trains.