Multi-beam antenna using higher-order modes

Abstract

Disclosed is an array antenna comprising a plurality of array elements. The plurality of array elements are formed as a coupler including a central element and peripheral elements configured to surround the central element; each of the central element and the peripheral elements is formed as a waveguide; and the peripheral elements are excited in higher-order modes using coupling slots to form a beam pattern through an electric field distribution of the central element and the peripheral elements.

What is claimed is: 
     
         1 . An array antenna comprising a plurality of array elements, wherein:
 the plurality of array elements consist of a central element and peripheral elements configured to surround the central element;   each of the central element and the peripheral elements is a waveguide; and   the peripheral elements excites higher-order modes through coupling slots to form a beam pattern by electric field distributions of the central element and the peripheral elements.   
     
     
         2 . The array antenna of  claim 1 , wherein a signal amplitude is zero at a center of each of the peripheral elements. 
     
     
         3 . The array antenna of  claim 2 , wherein:
 half of an aperture of each of the peripheral elements close to the central element has the same phase as an electric field of the central element; and   half of the aperture of each of the peripheral elements farther away from the central element has an opposite phase to the electric field of the central element.   
     
     
         4 . The array antenna of  claim 1 , wherein, among the peripheral elements, peripheral elements positioned at lateral sides of the central element has an electric field distribution of a TE21 mode rotated by 45°. 
     
     
         5 . The array antenna of  claim 1 , wherein, among the peripheral elements, peripheral elements positioned above and below the central element have an electric field distribution of a combination mode of a TM01 mode and a TE21 mode. 
     
     
         6 . The array antenna of  claim 1 , wherein a length of the coupler including the coupling slots is defined to be less than or equal to a length of a guided wavelength. 
     
     
         7 . The array antenna of  claim 1 , wherein the central element is disposed at a central portion of the array structure and is disposed at a distance of an interval between the array elements.