Electronically agile multi-beam antenna system

Abstract

The present invention provides an antenna system for use in determining N unknown parameter values relating to an object located in the vicinity of the system. One embodiment of the system includes a body with a longitudinal axis and a plane that is substantially perpendicular to the roll axis. The system further includes an antenna array comprised of a plurality of elements, each of which is located in a ring in the noted plane and separated from each of the other elements by less than 180° relative to the longitudinal axis. Also included in the improved antenna system is a beamformer for producing N+1 beams and a device for using the N+1 beams to determine N values associated with the object.

1 . An electronically agile antenna system comprising: 
 a body having an exterior surface, a longitudinal axis and a plane that is substantially perpendicular to said longitudinal axis;    an antenna array that is operatively connected to said body, has at least three elements that are each located in a first ring in said plane, and is capable of providing a plurality of signals that are representative of the environment about the antenna system, wherein each of said at least three elements is capable of providing one of said plurality of signals;    a beamformer that includes means for selecting a first portion of said plurality of signals provided by a first subset of elements of said plurality of elements to form a first beam and a second portion of said plurality of signals provided by a second subset of elements of said plurality of elements to form a second beam, wherein each element of said first subset of elements is separated from each element of said second subset of elements by less than about 180° relative to longitudinal axis, said beamformer further including means for processing said first portion of said plurality of signals to form said first beam, and means for processing said second portion of said plurality of signals to form said second beam; and    means for cooperatively using said first beam and said second beam to determine an unknown parameter value associated with an object located in the vicinity of said body.    
   
   
       2 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said body is a missile.    
   
   
       3 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said antenna array is substantially conformal to said exterior surface.    
   
   
       4 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said antenna array forms a portion of said exterior surface.    
   
   
       5 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said exterior surface includes a front surface and a side surface; and    substantially all said antenna array is located on said side surface.    
   
   
       6 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said antenna array has a field of view of approximately ±60° relative to said longitudinal axis.    
   
   
       7 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 at least one of said at least three elements includes a surface wave mode element.    
   
   
       8 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 at least one of said at least three elements includes one of the following: a wave guide feed and a printed circuit feed.    
   
   
       9 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 at least one of said at least three elements provides a broadband mode of operation.    
   
   
       10 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 at least one of said at least three elements has an endfire pattern.    
   
   
       11 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said at least three elements includes one of the following: at least three discrete elements, each with a feed and a lens, a single lens with at least three feeds, and a hybrid of at least one discrete element and a single lens with at least two feeds.    
   
   
       12 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 at least one of said at least three elements is one of the following: a radially polarized element and a circumferentially polarized element.    
   
   
       13 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 at least two elements have different polarization responses.    
   
   
       14 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said first ring has a substantially circular shape.    
   
   
       15 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said at least three elements that are each located in said first ring includes a discrete pair of elements, wherein a distance between the elements comprising said discrete pair of elements is predetermined to aid in resolving ambiguities in the determination of said unknown parameter value.    
   
   
       16 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said at least three elements that are each located in said first ring includes a first element, a second element that is located immediately adjacent to said first element, and a third element that is located immediately adjacent to said second element and separated from said first element by said second element, wherein a first distance between said first element and said second element is different than a second distance between said second element and said third element.    
   
   
       17 . An electronically agile antenna system, as claimed in  claim 16 , wherein: 
 said first distance is predetermined to aid in resolving ambiguities in the determination of said unknown parameter value.    
   
   
       18 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said at least three elements that are each located in said first ring includes at least two discrete pair of elements, wherein the two elements comprising each of said at least two discrete pair of elements are separated by a first distance and each of said at least two discrete pair of elements is separated from an immediately adjacent discrete pair of elements by a second distance that is greater than said first distance.    
   
   
       19 . An electronically agile antenna system, as claimed in  claim 18 , wherein: 
 a first of said at least two discrete pair of elements is separated from a second of said at least two discrete pair of elements by approximately 90° as measured from said longitudinal axis.    
   
   
       20 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said at least three elements are equally spaced from one another.    
   
   
       21 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said at least three elements that are each located in said first ring includes a plurality of pair of elements, wherein the two elements comprising each of said plurality of pair of elements are separated by a first distance and each of said plurality of pair of elements is separated from an immediately adjacent pair of elements by a second distance that is greater than said first distance and the distance between immediately adjacent pairs of elements is substantially equal.    
   
   
       22 . An electronically agile antenna system, as claimed in  claim 1  wherein: 
 said at least three elements that are each located in said first ring includes a plurality of pair of elements, wherein the two elements comprising each of said plurality of pair of elements are separated by a first distance and each of said plurality of pair of elements is separated from an immediately adjacent pair of elements by a second distance that is greater than said first distance and at least two immediately adjacent pair of elements have a different distance therebetween than between a different immediately adjacent pair of elements.    
   
   
       23 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said at least three elements that are each located in said first ring includes at least eight discrete pair of elements.    
   
   
       24 . An electronically agile antenna system, as claimed in  claim 22 , wherein: 
 said at least eight discrete pair of elements are substantially equally spaced from one another.    
   
   
       25 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said antenna array includes an element that is located in a second ring that is different than said first ring.    
   
   
       26 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said antenna array includes at least three radially polarized elements located in said first ring and at least three circumferentially polarized elements located in a second ring in said plane that is different than said first ring.    
   
   
       27 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said first subset of elements is immediately adjacent to said second subset of elements.    
   
   
       28 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said first subset of elements includes only one element;    said second subset of elements includes only one element; and    said first subset of elements is located immediately adjacent to said second subset of elements.    
   
   
       29 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said beamformer includes means for forming said first beam at a first time and said second beam at a second time that is later than said first time.    
   
   
       30 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said beamformer includes means for forming said first beam at substantially the same time as said second beam.    
   
   
       31 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said first beam is spatially independent but overlapping with said second beam.    
   
   
       32 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said means for cooperatively using includes means for performing an amplitude comparison of said first beam and said second beam.    
   
   
       33 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said means for cooperatively using includes means for performing a phase comparison of said first beam and said second beam.    
   
   
       34 . An electronically agile antenna system, as claimed in  claim 1 , wherein: 
 said means for cooperatively using includes means for performing an amplitude comparison and a phase comparison of said first beam and said second beam.    
   
   
       35 . An electronically agile, mobile antenna system for use in determining N unknown parameter values associated with an object located in the vicinity of the system, where N is at least three, comprising: 
 a body having an exterior surface, a longitudinal axis, and a plane that is substantially perpendicular to said longitudinal axis;    an antenna array that is operatively connected to said body, has a plurality of elements that are each located in a ring in said plane, and is capable of providing a plurality of signals that are each representative of the environment about the antenna system, wherein each of said plurality of elements is capable of providing one of said plurality of signals;    a beamformer for processing N+1 portions of said plurality of signals provided by N+1 subsets of said plurality of elements to produce N+1 beams, wherein each element of each of said N+1 subsets is separated from every other element of said N+1 subsets by less than about 180° relative to said longitudinal axis; and    means for cooperatively using said N+1 beams to determine said N unknown parameter values associated with the object, where N is at least three.    
   
   
       36 . An electronically agile, mobile antenna system, as claimed in  claim 35 , wherein: 
 said plurality of elements includes at least one radially oriented element; and    said means for cooperatively using includes means for compensating for an offset f(p) in phrase delta caused by said at least one radially oriented element whose phase and amplitude response at any given point in space varies based on element orientation.    
   
   
       37 . An electronically agile, mobile antenna system, as claimed in  claim 35 , wherein: 
 said plurality of elements are located substantially conformal to said exterior surface and include a discrete pair of elements; and    said discrete pair of elements are located substantially in said plane and are one of the following: in equal proximity to each other and in closer proximity to one another than to other of said plurality of elements.    
   
   
       38 . An electronically agile, mobile antenna system as claimed in  claim 35 , wherein: 
 said beamformer, when at least two of said N+1 beams to be provided to said means for cooperatively using are substantially linearly polarized and a phase difference therebetween is described by:      Δ= dsin ⊖ cos ø+ f ( p )    where f(p)→0, includes means for selecting said at least two of said N+1 beams based upon beam strength, phase ambiguity resolution, and desired baselines for azimuth and elevation determination.    
   
   
       39 . An electronically agile, mobile antenna system as claimed in  claim 35 , wherein: 
 said beamformer, when at least two of said N+1 beams to be provided to said means for cooperatively using are substantially circularly polarized and a phase difference therebetween is described by:      Δ= dsin⊖ cos ø+f ( p )    where f(p)=P·ø with P a constant, includes means for selecting said at least two of said N+1 beams based on signal strength, phase ambiguity resolution, desired baselines for azimuth and elevation determination, and multiple ø baselines for polarization ambiguity.    
   
   
       40 . An electronically agile, mobile antenna system as claimed in  claim 35 , wherein: 
 said beamformer, when at least two of said N+1 beams to be provided to said means for cooperatively using are one of linearly polarized and circularly polarized, and a phase difference therebetween is described by:      Δ= dsin⊖ cos ø+f ( p )    where f(p)=Pø and P=0 or P≠0, includes means for selecting said at least two of said N+1 beams based on signal strength, phase ambiguity resolution, desired baselines for azimuth and elevation determination, and multiple ø baselines for polarization ambiguity.    
   
   
       41 . An electronically agile mobile antenna system as claimed in  claim 35 , wherein: 
 said beamformer includes a look up table for polarization parameters γ n  and δ n  that is indexed based upon element location; and    said means for cooperatively using includes means for determining f(p), where f(p)=Ψ n pol−Ψ m pol, using said polarization parameters and a measured phase difference between beams.    
   
   
       42 . An electronically agile mobile antenna system as claimed in  claim 35 , wherein: 
 said means for cooperatively using, when at least two of said N+1 beams are of a known polarization and a location of an object is approximately known, includes means for determining f (p) and means for calculating location parameters of the object with two phase difference measurements.    
   
   
       43 . An electronically agile mobile antenna system as claimed in  claim 35 , wherein: 
 said beamformer includes means for selecting said N+1 beams such that said N+1 beams are derived from N+1 portions of said plurality of signals produced by a group of said plurality of elements that are located substantially adjacent to one another.    
   
   
       44 . An electronically agile mobile antenna system as claimed in  claim 35 , wherein: 
 said beamformer includes means for selecting said N+1 beams such that said N+1 beams are derived from N+1 portions of said plurality of signals produced by elements located substantially on opposite sides of said ring to achieve substantially 180° spatial separation for high resolution measurements in a reduced field of view.    
   
   
       45 . An electronically agile, mobile antenna system, as claimed in  claim 35 , wherein: 
 each of said plurality of elements is a broadband launch element.    
   
   
       46 . An electronically agile, mobile antenna system, as claimed in  claim 35 , wherein: 
 said plurality of elements includes a plurality of discrete pair of elements.    
   
   
       47 . An electronically agile, mobile antenna system, as claimed in  claim 35 , wherein: 
 said plurality of elements includes at least two discrete pair of elements and no more than eight discrete pair of elements.    
   
   
       48 . An electronically agile, mobile antenna system, as claimed in  claim 35 , wherein: 
 each of said N+1 subsets of said plurality of elements includes only one element.    
   
   
       49 . An electronically agile, mobile antenna system, as claimed in  claim 35 , wherein: 
 said beamformer includes only one beamforming channel and means for sequentially using said only one beamformer channel to produce said N+1 beams.    
   
   
       50 . An electronically agile, mobile antenna system, as claimed in  claim 35 , wherein: 
 said beamformer includes more than one beamforming channel and less than N+1 beamforming channels, and means for simultaneously using said more than one beamforming channels to form less than said N+1 beams, and means for later using at least one of said more than one beamforming channels to generate the remaining N+1 beams.    
   
   
       51 . An electronically agile, mobile antenna system, as claimed in  claim 35 , wherein: 
 said beamformer includes N+1 beamforming channels and means for simultaneously using said N+1 beamforming channels to produce said N+1 beams.    
   
   
       52 . An electronically agile, mobile antenna system, as claimed in  claim 35 , wherein: 
 said beamformer includes more than N+1 channels and means for simultaneously using said more than N+1 channels to form more than said N+1 beams to provide greater accuracy.    
   
   
       53 . An electronically agile, mobile antenna system, as claimed in  claim 35 , wherein: 
 at least two of said N+1 beams are spatially independent and overlapping.    
   
   
       54 . An electronically agile, mobile antenna system, as claimed in  claim 35 , wherein: 
 all of said N+1 beams are spatially independent and overlapping.    
   
   
       55 . An electronically agile, mobile antenna system for determining N unknown parameter values associated with an object in the vicinity of the system, where N is at least three, comprising: 
 a body having an exterior surface, a longitudinal axis, and a plane that is substantially perpendicular to said longitudinal axis;    an antenna array that is operatively connected to said body, has a plurality of discrete pair of broadband elements that are each located in a ring in said plane, and is capable of providing a plurality of signals that are each representative of the environment about the antenna system, wherein each element of said plurality of discrete pair of elements is capable of providing one of said plurality of signals;    a beamformer for processing N+1 of said plurality of signals provided by N+1 elements of said plurality of discrete pair of broadband elements to produce N+1 beams, wherein each element of said N+1 elements is separated from every other element of said N+1 elements by less than about 180° relative to said longitudinal axis; and    means for cooperatively using said N+1 beams to determine said N unknown parameter of values, where N is at least three.    
   
   
       56 . An electronically agile, mobile antenna system, as claimed in  claim 55 , wherein: 
 said beamformer includes means for forming a first beam from a first signal provided by a first broadband element of a discrete pair of broadband elements and a second beam from a second broadband element of the same said discrete pair of broadband elements.    
   
   
       57 . An electronically agile, mobile antenna system, as claimed in  claim 55 , wherein: 
 said beamformer includes means for forming a first beam from a first signal provided by a first broadband element of a first discrete pair of broadband elements, a second beam from a second signal provided by a second broadband element of said first discrete pair of broadband elements, and a third beam from a third signal provided by a third element of a second discrete pair of broadband elements that is different than said first discrete pair of broadband elements.    
   
   
       58 . An electronically agile, mobile antenna system, as claimed in  claim 57 , wherein: 
 said third element is separated from said first and second elements by less than 90° relative to said longitudinal axis.    
   
   
       59 . An electronically agile, mobile antenna system, as claimed in  claim 57 , wherein: 
 said third element is separated from said first and second elements by approximately 90° relative to said longitudinal axis.    
   
   
       60 . An electronically agile, mobile antenna system, as claimed in  claim 55 , wherein: 
 said beamformer includes means for forming first and second beams from first and second signals provided by a first discrete pair of broadband elements and means for forming third and fourth signals from a second discrete pair of broadband elements that is different than said first pair of discrete broadband elements.    
   
   
       61 . An electronically agile, mobile antenna system, as claimed in  claim 60 , wherein: 
 said first pair of broadband elements is separated from said second pair of broadband elements by less than 90° relative to said longitudinal axis.    
   
   
       62 . An electronically agile, mobile antenna system, as claimed in  claim 60 , wherein: 
 said first pair of broadband elements is separated from said second pair of broadband elements by approximately 90° relative to said longitudinal axis.    
   
   
       63 . An electronically agile, mobile antenna system, as claimed in  claim 60 , wherein: 
 said beamformer includes means for selecting said N+1 beams such that said N+1 beams are derived from N+1 portions of said plurality of signals produced by elements located substantially on opposite sides of said ring to achieve substantially 180° spatial separation for high resolution measurements in a reduced field of view.    
   
   
       64 . A method for operating an electronically agile, mobile antenna system for determining N unknown parameter values associated with an object in the vicinity of said system, where N is at least three, comprising: 
 providing a body having an exterior surface, a longitudinal axis, and a plane that is substantially perpendicular to said longitudinal axis;    providing an antenna array that is operatively connected to said body, has a plurality of elements that are each located in a ring in said plane, and is capable of providing a plurality of signals that are representative of the environment about the antenna system, wherein each of said elements is capable of providing one of said plurality of signals;    forming a first plurality of beams from said plurality of signals provided by said antenna array;    acquiring coarse information on the location of the object by comparing the amplitudes of said first plurality of beams to one another;    forming, following said step of acquiring, a second plurality of beams from N+1 portions of said plurality of signals provided by N+1 subsets of said plurality of elements to produce N+1 beams, wherein each element of each of said N+1 subsets is separated from every other element of said N+1 subsets by less than about 180° relative to said roll axis; and    tracking fine information on the object by comparing the phases of said second plurality of beams to one another to determine at least N unknown parameter values, where N is at least three.    
   
   
       65 . A method, as claimed in  claim 64 , wherein: 
 said step of forming a first plurality of beams includes forming at least one of said plurality of beams at a different time than another of said first plurality of beams.    
   
   
       66 . A method, as claimed in  claim 64 , wherein: 
 said step of forming a first plurality of beams includes forming all of said first plurality of beams at substantially the same time.    
   
   
       67 . A method, as claimed in  claim 64 , wherein: 
 said step of forming a second plurality of beams includes forming at least one of second plurality of beams at a different time than another of said second plurality of beams.    
   
   
       68 . A method, as claimed in  claim 64 , wherein: 
 said step of forming a second plurality of beams includes forming all of said second plurality of beams at substantially the same time.    
   
   
       69 . A method, as claimed in  claim 64 , wherein: 
 said step of forming a second plurality of beams includes forming spatially independent and overlapping beams.    
   
   
       70 . A method, as claimed in  claim 64 , wherein: 
 said step of tracking includes comparing a first phase of a first beam produced using a first subset of said plurality of elements to a second phase of a second beam produced from using a second subset of said plurality of elements, wherein said first subset of elements is separated from said second subset of elements by less than 90° relative to said roll plane.    
   
   
       71 . A method, as claimed in  claim 64 , wherein: 
 said step of tracking includes comparing a first phase of a first beam produced using a first subset of elements of said plurality of elements to a second phase of a second beam produced using a second subset of said plurality of elements, wherein said first subset of elements is separated from said second subset of elements by approximately 90°.    
   
   
       72 . A method, as claimed in  claim 64 , wherein: 
 said step of forming includes selecting said N+1 beams such that said N+1 beams are derived from N+1 portions of said plurality of signals produced by elements located substantially on opposite sides of said ring to achieve substantially 180° spatial separation for high resolution measurements in a reduced field of view.