Electronically agile dual beam antenna system

Abstract

The present invention provides an improved antenna system that, in one embodiment, includes an antenna array comprised of a plurality of elements, each of which is capable of providing a signal. Also included in the improved antenna system is, a multi-beam beamformer for producing two spatially independent overlapping beams from the signals provided by two different subsets of the antenna array. The phase of the two beams is compared to realize an interferometer that can provide high or fine resolution data on the position of an object relative to the antenna system. The amplitude of the two beams can also be compared to obtain coarse data on the position of the object. The beamformer includes a switching network for selecting which elements of the antenna array form the two subsets. This permits, for example, the position of the beams to moved, the baseline of the two beams to be varied, and/or the beam width of the beams to be altered. To reduce adverse aerodynamic effects in certain applications, the antenna array is located conformal to the exterior surface of the body on which the array is mounted. Further, to reduce temperature related problems associated with high speed movement of the body on which the array is located, the array is located on the side of the body, as opposed to the front of the body. The side location also provides space for other types of sensors that are preferably located adjacent to the front surface of the body.

What is claimed is:  
     
         1 . An electronically agile antenna system comprising: 
 a body having an exterior surface;    an antenna array that is operatively connected to said body, has a plurality of elements, and is capable of providing a plurality of signals that are representative of the environment about the antenna system, each of said plurality of elements being capable of providing one of said plurality of signals;    a beamformer for processing a first portion of said plurality of signals provided by said antenna array to form a first beam and for processing a second portion of said plurality of signals provided by said antenna array to form a second beam; and    means for cooperatively using said first beam and said second beam to determine information relating to the environment about the antenna system; said beamformer includes means for selecting which of said plurality of signals are used to form said first beam and which of said plurality of signals are used to form said second beam.    
     
     
         2 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said second beam is spatially independent but overlapping with said first beam.    
     
     
         3 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said plurality of elements of said antenna array includes more than two elements.    
     
     
         4 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said means for selecting includes means for changing the identity over time of which of said plurality of signals are used to form at least one of the following: said first beam and said second beam.    
     
     
         5 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said beamformer forms said first beam at substantially the same time as said second beam; and    said means for selecting includes means for changing the identity over time of which of said plurality of signals are used to form said first beam and which of said plurality of signals are used to form said second beam to vary the baseline between said first beam and said second beam.    
     
     
         6 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said means for selecting includes means for changing over time the number of said plurality of signals that are used to form at least one of the following: said first beam and said second beam.    
     
     
         7 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said beamformer forms said first beam at substantially the same time as said second beam; and    said means for selecting includes means for changing over time the number of said plurality of signals that are used to form said first beam and the number of said plurality of signals that are used to form said second beam to change the beamwidth of said first beam and said second beam, respectively.    
     
     
         8 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said means for using includes means for performing an amplitude comparison of said first beam and said second beam.    
     
     
         9 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said means for using includes means for performing a phase comparison of said first beam and said second beam.    
     
     
         10 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said means for using includes means for performing an amplitude comparison and a phase comparison of said first beam and said second beam.    
     
     
         11 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said beamformer includes a gallium arsenide field-effect transistor amplifier.    
     
     
         12 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said means for selecting includes an absorptive gallium arsenide field-effect transistor switch.    
     
     
         13 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said antenna array is substantially conformal to said exterior surface.    
     
     
         14 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said exterior surface includes a front surface and a side surface; and    said antenna array is located on said side surface.    
     
     
         15 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said plurality of elements includes a transmit portion for transmitting a signal and a receive portion for receiving a signal.    
     
     
         16 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said exterior surface includes a plurality of facets, and a portion of said antenna array is located on each facet.    
     
     
         17 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said exterior surface includes a plurality of facets, each facet supporting a first portion of said antenna array and a second portion of said antenna array that is separated from said first portion of said antenna array.    
     
     
         18 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said plurality of elements includes a log periodic element.    
     
     
         19 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said antenna array includes a plurality of juxtaposed elements with the spacing between said plurality of juxtaposed elements being tapered.    
     
     
         20 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said antenna array includes a first array of horizontally juxtaposed elements and a second array of horizontally juxtaposed elements, wherein said first array is vertically juxtaposed with respect to said second array.    
     
     
         21 . An electronically agile antenna system comprising: 
 a body that is capable of moving, has a longitudinal axis, and has an exterior surface comprised of a side surface and a front surface;    an antenna array that is operatively connected to said body and has a low profile with respect to said exterior surface, has a plurality of elements, and is capable of providing a plurality of signals that are representative of the environment about the antenna system, each of said plurality of elements being capable of providing one of said plurality of signals;    a multi-beam beamformer for processing a first portion of said plurality of signals to form a first beam and a second portion of said plurality of signals to form a second beam; and    means for using said first beam and said second beam to determine information relating to the environment about the antenna system.    
     
     
         22 . An electronically agile antenna system, as claimed in  claim 21 , wherein: 
 said body is a missile.    
     
     
         23 . An electronically agile antenna system, as claimed in  claim 21 , wherein: 
 said means for using includes means for cooperatively using said first beam and said second beam.    
     
     
         24 . An electronically agile antenna system, as claimed in  claim 21 , wherein: 
 said antenna array is conformal to said exterior surface.    
     
     
         25 . An electronically agile antenna system, as claimed in  claim 21 , wherein: 
 said multi-beam beamformer includes means for selecting which of said plurality of signals is used to form said first beam and which of said plurality of signals is used to form said second beam.    
     
     
         26 . An electronically agile antenna system, as claimed in  claim 21 , wherein: 
 said means for using includes means for performing at least one of the following: an amplitude comparison and a phase comparison of said first beam and said second beam.    
     
     
         27 . An electronically agile antenna system, as claimed in  claim 21 , wherein: 
 at least a portion of said antenna array is located on said side surface.    
     
     
         28 . An electronically agile antenna system, as claimed in  claim 21 , wherein: 
 a first element of said plurality of elements is located on said side surface and in a lateral plane relative to said longitudinal axis; and    a second element of said plurality of elements is located on said side surface and in said lateral plane.    
     
     
         29 . An electronically agile antenna system, as claimed in  claim 21 , wherein: 
 a first element of said plurality of elements is located on said side surface and at a first distance along said longitudinal axis; and    a second element of said plurality of elements is located on said side surface, substantially in line with said first element, and at a second distance along said longitudinal axis that is different than said first distance.    
     
     
         30 . An electronically agile antenna system, as claimed in  claim 29 , wherein: 
 said first element is used to receive a signal and said second element is used to do one of the following: receive a signal and transmit a signal.    
     
     
         31 . An electronically agile antenna system, as claimed in  claim 21 , wherein: 
 a first element of said plurality of elements is located on said side surface; and    a second element of said plurality of elements is located on said side surface and opposite to said first element relative to said longitudinal axis.    
     
     
         32 . An electronically agile antenna system, as claimed in  claim 21 , wherein: 
 a first pair of said plurality of elements with one element located opposite to the other element relative to said longitudinal axis, said first pair being capable of providing a first pair of signals of said plurality of signals;    a second pair of said plurality of elements with one element located opposite to the other element relative to said longitudinal axis, said second pair being capable or providing a second pair of signals of said plurality of signals; and    said multi-beam beamformer includes means for selecting which of said first pair of signals and said second pair of signals is used to form said first beam and said second beam.    
     
     
         33 . An electronically agile antenna system, as claimed in  claim 21 , wherein: 
 a first pair of said plurality of elements that is located on said side surface and in a lateral plane relative to said longitudinal axis and is capable of providing a first pair of signals of said plurality of signals;    a second pair of said plurality of elements that is located on said side surface and in said lateral plane and is capable or providing a second pair of signals of said plurality of signals; and    said multi-beam beamformer includes means for selecting which of said first pair of signals and said second pair of signals is used to form said first beam and said second beam.    
     
     
         34 . An electronically agile antenna system, as claimed in  claim 21 , wherein: 
 a first pair of said plurality of elements that is located on said side surface, substantially in line with one another, and with one of said first pair at a first distance along said longitudinal axis and the other at a second distance along said longitudinal axis that is different than said first distance, and is capable of providing a first pair of signals of said plurality of signals;    a second pair of said plurality of elements that is located on said side surface, substantially in line with one another, and with one of said second pair at said first distance along said longitudinal axis and the other at said second distance along said longitudinal axis, and is capable of providing a second pair of signals of said plurality of signals; and    said multi-beam beamformer includes means for selecting which of said first pair of signals and said second pair of signals is used to form said first beam and said second beam.    
     
     
         35 . An electronically agile antenna system, as claimed in  claim 21 , wherein: 
 a portion of said plurality of elements has an endfire pattern.    
     
     
         36 . An electronically agile antenna system, as claimed in  claim 21 , wherein: 
 a first portion of said plurality of elements has a first pattern that covers a first field of view relative to said longitudinal axis; and    a second portion of said plurality of elements has a second pattern that covers a second field of view relative to said longitudinal axis that substantially avoids overlapping with said first field of view.    
     
     
         37 . An electronically agile antenna system, as claimed in  claim 35 , wherein: 
 said first pattern includes an endfire pattern.    
     
     
         38 . An electronically agile antenna system, as claimed in  claim 21 , wherein: 
 a first portion of said plurality of elements is used to transmit a signal and a second portion of said plurality of elements is used to receive a signal.    
     
     
         39 . An electronically agile antenna system, as claimed in  claim 21 , further including: 
 a sensor that is located at one of the following: in between said front surface and said antenna array and in between said plurality of elements.    
     
     
         40 . An electronically agile antenna system comprising: 
 providing an antenna array that has a plurality of elements and is capable of providing a plurality of signals that are representative of the environment about the antenna system, each of said plurality of elements being capable of providing one of said plurality of signals;    using a first subset of said plurality of signals to form a first beam;    using a second subset of said plurality of signals that is different than said first subset to form a second beam;    cooperatively using said first beam and said second beam to determine information relating to the environment about the antenna system; and    electronically changing said first subset and said second subset; and    repeating said steps of using a first subset, using a second subset, and using said first beam and second beam.    
     
     
         41 . An electronically agile antenna system, as claimed in  claim 40 , wherein: 
 said step of electronically changing includes electronically changing the number of signals in said first subset and said second subset.    
     
     
         42 . An electronically agile antenna system, as claimed in  claim 40 , wherein: 
 said step of electronically changing includes electronically changing the identity of the signals in said first subset and said second subset.    
     
     
         43 . An electronically agile antenna system, as claimed in  claim 40 , wherein: 
 said step of using said first beam and said second beam includes performing an amplitude comparison of said first beam to said second beam.    
     
     
         44 . An electronically agile antenna system, as claimed in  claim 40 , wherein: 
 said step of using a second subset of said plurality of signals to form a second beam occurs after said step of using a first subset of said plurality of signals to form a first beam.    
     
     
         45 . An electronically agile antenna system, as claimed in  claim 40 , wherein: 
 said step of using said first beam and said second beam includes performing a phase comparison of said first beam to said second beam.    
     
     
         46 . An electronically agile antenna system, as claimed in  claim 40 , wherein: 
 said step of using said first beam and said second beam includes performing an amplitude comparison of said first beam to said second beam followed by a phase comparison of said first beam to said second beam.    
     
     
         47 . An electronically agile antenna system, as claimed in  claim 40 , wherein: 
 said step of electronically changing includes electronically changing the identity of the signals in the first subset and the second subset so that said first and second beams dither about a cross-plane.    
     
     
         48 . An electronically agile antenna system, as claimed in  claim 40 , wherein: 
 said step of electronically changing said first subset and said second subset changes an aperture of said antenna array.