Sparse Phased-Array-Fed Focusing Aperture Antennas With Reduced Grating Lobes

Abstract

An apparatus includes a plurality of antenna feed elements arranged in an array and a reflector or lens. The reflector or lens is configured to focus a first signal generated by the plurality of antenna feed elements or focus a second signal not generated by the plurality of antenna feed elements onto the plurality of antenna feed elements. The apparatus further includes a controller or processor configured to control the plurality of antenna feed elements to generate the first signal or receive the second signal. The first signal and the second signal have a nominal wavelength. The plurality of antenna feed elements are spaced from one another in the array at a distance greater than half of the nominal wavelength.

What is claimed is: 
     
         1 . An apparatus comprising:
 a plurality of antenna feed elements arranged in an array;   a reflector or lens configured to:
 focus a first signal generated by the plurality of antenna feed elements, or 
 focus a second signal not generated by the plurality of antenna feed elements onto 
   the plurality of antenna feed elements; and   a controller or processor configured to control the plurality of antenna feed elements to generate the first signal or receive the second signal, wherein:   the first signal and the second signal have a nominal wavelength,   the plurality of antenna feed elements are spaced from one another in the array at a distance greater than half of the nominal wavelength.   
     
     
         2 . The apparatus of  claim 1 , wherein the plurality of antenna feed elements are spaced from one another in the array at a distance equal to or greater than 0.6 times the nominal wavelength. 
     
     
         3 . The apparatus of  claim 1 , wherein the plurality of antenna feed elements are spaced from one another in the array at a distance equal to or greater than 0.7 times the nominal wavelength. 
     
     
         4 . The apparatus of  claim 1 , wherein the plurality of antenna feed elements are spaced from one another in the array at a distance equal to or greater than 0.75 times the nominal wavelength. 
     
     
         5 . The apparatus of  claim 1 , wherein the plurality of antenna feed elements are spaced from one another in the array at a distance between 0.6 and 0.8 times the nominal wavelength. 
     
     
         6 . A method for using the apparatus of  claim 1 , wherein only a subset of the plurality of antenna feed elements are used to generate a third signal or receive a fourth signal. 
     
     
         7 . The method of  claim 6 , wherein the subset of the plurality of antenna feed elements comprises less than half of the plurality of antenna feed elements. 
     
     
         8 . The apparatus of  claim 1 , wherein the reflector or lens comprises a gradient index (GRIN) lens. 
     
     
         9 . The apparatus of  claim 1 , wherein the reflector or lens comprises a plurality of gradient index (GRIN) lenses. 
     
     
         10 . The apparatus of  claim 9 , wherein the plurality of GRIN lenses are positioned in series such that the first signal or the second signal passes through each of the plurality of GRIN lenses. 
     
     
         11 . The apparatus of  claim 9 , wherein the plurality of GRIN lenses are each positioned to be associated with one or more of, but not all of, the plurality of antenna feed elements. 
     
     
         12 . A method comprising:
 focusing, with a reflector or lens, a signal tot generated by a plurality of antenna feed elements onto the plurality of antenna feed elements, wherein the plurality of antenna ked elements are arranged in an array; and   controlling, by a controller or processor, the plurality of antenna feed elements to generate a representation of the signal by combining signals received by at least a subset of the plurality of antenna feed elements, wherein;
 the signal has a nominal wavelength, 
 the plurality of antenna feed elements are spaced from one another in the array at a distance greater than half of the nominal wavelength. 
   
     
     
         13 . The method of  claim 12 , wherein the plurality of antenna feed elements are spaced from one another in the array at a distance between 0.6 and 0.8 times the nominal wavelength. 
     
     
         14 . The method of  claim 12 , wherein less than half of the plurality of antenna feed elements are used for the combining of the signals received by the subset of the plurality of antenna feed elements. 
     
     
         15 . The method of  claim 12 , wherein the reflector or lens comprises at least one gradient index (GRIN) lens. 
     
     
         16 . The method of  claim 12 , wherein the signal is a first signal and the subset of the plurality of antenna feed elements is a first subset of the plurality of antenna feed elements, and the method further comprises:
 controlling, by the controller or processor, the plurality of antenna feed elements to generate a second signal by outputting a plurality of signals using a second subset of the plurality of antenna feed elements, wherein a combination of the plurality of signals is representative of the second signal; and   focusing, with a reflector or lens, the second signal generated by the plurality of antenna feed elements to emit the second signal.   
     
     
         17 . An electromagnetic antenna comprising:
 a first and second feed element adjacent to each other and configured to simultaneously radiate a first and second signal, the first signal having a first frequency, a first amplitude and a first phase, the second signal having a second frequency, a second amplitude and a second phrase referenced to the phase of the first signal, wherein:
 the first frequency is equal to the second frequency; 
 the first amplitude is equal to or larger than the second amplitude by between a factor of −10 dB and 10 dB; 
 the first phase is different from the second phase by a predetermined angle between 0 and 360 degrees; and 
 the first and second feed elements being spaced apart by, a predetermined distance between 0.5λ and 1λ, wherein λ is a wavelength of an operating frequency; 
   a millimeter wave (MMW) printed circuit board (PCB) comprising a multi-channel beamforming circuit configured to supply the first and second signals, where the multi-channel beamforming circuit is further configured to transform a third signal into the first and second signal;   a planar focal surface on which the first and second feed elements are mounted; and   an electromagnetic lens configured to focus the first and second signals for transmission.   
     
     
         18 . The electromagnetic antenna of  claim 17 , wherein the electromagnetic lens comprises a compound lens having first and second lens elements arranged in series, wherein the compound lens focuses and both the first and second signals and is associated with the first and second feed elements. 
     
     
         19 . The electromagnetic antenna of  claim 18 , wherein the first lens element provides greater focusing than the second lens element, and further wherein the second lens element squints the first and second signals in aggregate toward the first lens. 
     
     
         20 . The electromagnetic antenna of  claim 19 , wherein each of the first and second lens elements comprises a gradient index (GRIN) lens. 
     
     
         21 . The electromagnetic antenna of  claim 17 , wherein the electromagnetic lens comprises at least a first lens element and a second lens element arranged in parallel to one another, wherein:
 the first lens element focuses the first signal and is associated with the first feed element, and   the second lens element focuses the second signal and is associated with the second feed element.   
     
     
         22 . The electromagnetic antenna of  claim 17 , wherein λ is in a range between 3.75 mm and 37.5 mm.