Journal of Communication Engineering

Journal of Communication Engineering

Grating-Lobe Reduction for Non-Uniform Linear Sub-Array Using High order mode

Document Type : Research Paper

Authors
M. Etebarian Khorasgani
A. Ghorbani
Department of Electrical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran.
10.22070/jce.2025.20912.1289
Abstract
In antenna theory, a sub-array is a group of smaller antennas arranged into an array. It is a collection of smaller elements in the structure of an array antenna. Not only does this structure have advantages for performance antennas, but also the sub-array has problems, such as the occurrence of grating lobes (GLs) in the radiation pattern. Some of the advantages of these structures are reduced complexity, cost efficiency, and system flexibility. GLs are unwanted patterns that occur when the spacing between antenna elements is large relative to the signal wavelength. These lobes can appear in undesirable directions, decreasing the antenna's performance, including its directivity and gain. There are several methods for GL reduction, including reducing element spacing, using non-uniform or random spacing to disrupt periodicity, applying beamforming weights to suppress sidelobes, and employing multi-subarray techniques for additional control. The main approach to reducing GLs is to introduce a null in the radiation pattern using the high-order mode technique. This means that when the element pattern is a multiple of the array pattern, the GL is omitted from the pattern at -40 degrees. It is possible to change the radiation direction of an antenna by combining two modes. In other words, the beam scan in the element depends on the current excitation mode. Thus, each mode is excited by a coaxial cable, and each antenna element has two power supplies. Simulation results show that the reduction of GL is -21.54 dB.
Keywords
Grating lobe reduction
Subarray antenna
High order mode
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