Development of a compact metasurface antenna with reconfigurable pattern through mode combination technique for 5G mm-wave applications

This paper presents a compact metasurface antenna with reconfigurable radiation patterns designed for 5G mm-wave applications. The antenna consists of a metasurface with 3 × 3 unit cells of modified patches, two coupling slots on the ground plane, and a reconfigurable feeding network. The method of characteristic mode analysis is initially employed to identify the modes of the metasurface layer which are responsible for steering the radiation pattern of the antenna at angles of 0° and ±30°. By analysing the surface currents of these modes, the locations of the coupling slots are determined, making it easier to excite and combine the desired modes and steer the main beam of the antenna in specific directions. The pattern reconfigurability is achieved by switching PIN diodes in the microstrip feed network to excite the appropriate coupling slots. The proposed metasurface antenna, with dimensions of 0.9λ₀ × 0.9λ₀ × 0.08λ₀ (where λ₀ is the free space wavelength at the centre frequency of 27 GHz), was fabricated and tested. The experimental results showed a wide bandwidth of 22.71% achieved by combining the resonance frequencies of the slots and metasurface layer. Furthermore, the antenna exhibits three distinct main beams at +30°, 0°, and −30° with a peak gain of 8.95 dB.