Analysis and design of a passive spatial filter for sub-6 GHz 5G communication systems

A frequency-selective surface (FSS) is able to transmit or reflect incoming electromagnetic waves, and these properties of FSS can be utilized in printed antennas to improve the performance of these antennas. Sub-6 GHz frequency bands are used in fifth-generation (5G) systems for various applications. This paper presents the design and analysis of a wideband band-pass spatial filter using a double square loop frequency-selective surface (DSLFSS) for the sub-6 GHz 5G frequency range 1 (FR1). The proposed spatial filter consists of DSLFSS elements and can be placed on the patch radiator to increase the radiation characteristics in n77, n78, and n79 bands of the sub-6 GHz 5G spectrum. The effect of varying the width of the loops, angle of incidence. and polarization on the transmission coefficient in the frequency band of operation is analyzed. The design is synthesized using the closed form mathematical expressions for finding the physical dimensions of the spatial filter. Design trade-offs are reported based on the proposed mathematical formulation and simulations. The designed DSLFSS structure is fabricated and measured. The design results are authenticated by comparing results from the Ansys HFSS v20 Electronic Desktop Circuit Editor and measurement setup. In addition, the extension of the results from a unit cell is taken to the \(2 \times 2\) array and \(10 \times 10\) array, which shows nearly the same performance, hence confirming the stability of the DSLFSS structure. The proposed DSLFSS-based spatial filter has the potential for use in the design and development of patch radiators with improved radiation characteristics.