Interwoven Hexagonal Frequency Selective Surface: An Application for WiFi Propagation Control

Abstract

A sub-wavelength band stop unit cell Frequency Selective Surface, comprising six continuously interwoven hexagonal unit cells and arranged as a tessellated surface, is proposed, analyzed, simulated, and measured. The broadband and sub-wavelength characteristics of this unit cell, below the typical λ 0 /2, are analyzed and discussed. It has been demonstrated that by using the unit cell proposed in this paper, a 22% increase in the fractional bandwidth can be achieved along with a substantial improvement in its angular stability at high angles of incidence, compared to similar works previously published. The analysis of this unit cell is performed using the equivalent circuit method that allows relating the number of interweaves with the equivalent capacitance and inductance, thus giving a better understanding of the unit cell characterization. In addition, a frequency selective surface arranged in a 2.5D configuration is also proposed. This 2.5D configuration provides a bandwidth similar to the conventional model but with a reduction in the resonance frequency by 44%. Simulations have been validated using two prototypes, each having an overall dimension of 400 x 400 mm. To demonstrate the scalability of the design, both prototypes are designed to be used as WiFi propagation control, working as a band stop filter at 2.4 and 5.8 GHz, respectively. Transmission coefficients have been measured for TE and TM-modes using an optical bench at angles of incidence from 0 to 60 • . These compare favorably with simulations performed using the frequency domain solver in CST Microwave Studio and are found to have a maximum MSE of 2.3 ×10 −3 .

Multibeam Beamforming for Direct Radiating Arrays in Satellite Communications Using Genetic Algorithm

“…In this design, the array is configured in a hexagonal lattice layout, a choice motivated by the packing density of elements within a given area, improving that of square or rectangular configurations. This arrangement effectively minimizes the emergence of grating lobes, as detailed by [32]. According to the Array Dimensioning section, the configuration will incorporate an 8×8 matrix of elements, with an inter-element spacing of 0.74λ 0 , predicated on the assumption of minimal mutual coupling.…”

Triangular Intertwined Frequency Selective Surface

“…λ 0 /p Fractional bandwidth (%) Trifilar spiral [3] 34.72 17.98 Hexafilar spiral [3] 26.94 69.91 Intertwined Hexagonal [5] 18.617 90.2 Intertwined Triangular 34.8 55 Intertwined Triangular (MEFSS) 47.9 28…”

“…These structures are electromagnetic filters whose frequency response depends upon the impinging polarization and angle of incidence of the electromagnetic wave. Some authors have researched different intertwined structures for propagation control applications; for instance, some principal designs are: convoluted cross spiral [1], quadrifilar spiral [2], trifilar spiral [3], hexafilar spiral [3], intertwined Brigid's cross [4], and intertwined hexagonal structure [5]. All previous structures can be used as band band-pass filters (inductive FSS) or band-stop filters (capacitive FSS).…”

2.5D Inductive Intertwined Frequency Selective Surface For Pass-Band Applications

“…One of the techniques used to improve FSS miniaturization is the so-called 2.5D configuration, which consists of using vias to connect two or more FSS layers. As we increase the number of layers, the surface current finds a new path that will increase the inductance, improving the miniaturization, but with reduced bandwidth [2]. Some authors have presented different designs to obtain a pass-band structure at different frequency bands in the This work was supported by the Luxembourg National Research Fund (FNR), through the CORE Project (ARMMONY): Ground-based distributed beamforming harmonization for the integration of satellite and Terrestrial networks, under Grant FNR16352790.…”