Side lobe level reduction of metasurface transmit array

Abstract

This paper presents a study on the side-lobe level (SLL) reduction with transmission type metasurface (MTS) using the concept of non-uniform array technique and transmit array antenna. According to the non-uniform antenna array technique, the SLL can be controlled by controlling the amplitude and phase distribution simultaneously. Initially, transmit array concept is used to design the MTS. The radiation characteristics of the MTS antenna are analyzed by exciting with a rectangular patch antenna at a fixed feed position. The simulation results show a gain of 17.6 dB with SLL of −18.3 and −19 dB in ϕ = 0° and 90°-planes, respectively. Later, non-uniform array techniques are used to reduce the SLL by introducing various amplitude distribution functions on the MTS for a fixed focal distance. The MTS incorporates the amplitude tapering functions such as Kaiser, Hamming, Hanning, and Blackman distribution functions. The resulting SLLs are analyzed, and the achieved SLLs are far from the theoretical values. In order to further reduce and control the SLL, the Gaussian distribution function is used, which minimizes the SLL by optimizing the standard deviation(σ). A MTS with 16 × 16 unitcells is fabricated and measured with an optimized σ = 0.31. The measured SLL are −25.1 and −26.3 dB in ϕ = 0° and 90°-planes, respectively.