High-Gain Flat-Top Antenna Sub-Arrays for Planar Arrays with Limited Field of View

This paper presents an antenna array which is based on a novel sub-array architecture. Each sub-array is a linear array of open-ended waveguides. The central element of the sub-array is directly fed, while the other elements are short-circuited. The position of the short circuits along the waveguides controls the radiation pattern properties and scattering parameters evaluated at the active ports of the array. The proposed sub-array structure exhibits high-gain characteristics with a flat-top distribution and is used as a unit cell in a two-dimensional array. The distance between the subarray centers along the relevant main axis is large in terms of wavelengths, which leads to limited scanning capabilities, whereas the inter-element separation along the orthogonal plane is about half free-space wavelength at the central working frequency, this leading to a wide scan range. Using the presented approach, an array operating at 28.5 GHz was designed in such a way as to feature a maximal scanning angle of ±7.4° along the E-plane and ±27.45° along the H-plane. The specific sub-array pattern, which approximates a rectangular pulse distribution, allows to filter out the grating lobes along the E-plane.