In this paper, a low-profile broadband frequency selective surface (FSS) is presented for wideband shielding. The FSS consists of periodic patterns of circular loops connected among themselves through varactor diodes, which exhibit tunable operation. The novelty of the proposed design lies in its wideband tuning, where the bandstop response can be varied from 0.54 to 2.50 GHz under the reverse bias voltage, thereby exhibiting a tunable range of 363%. Moreover, the structure exhibits a wide 1.28 GHz stopband (fractional bandwidth of 152%), which is maximum as compared to other wideband FSSs. Additionally, the design is polarization-insensitive and angularly stable for both TE and TM polarizations. A prototype of the proposed structure has been fabricated where the varactor diodes are biased through a novel biasing technique. The sample is measured using parallel-plate waveguide setup as well as the free-space technique, where the measured results show good agreement with the simulated responses.

Broadband Polarization-Insensitive Tunable Frequency Selective Surface for Wideband Shielding

A novel broadband bandpass frequency-selective surface (FSS) designed for fifth generation (5G) EMI shielding is proposed in this paper. This new design employs the vertical vias into the 2-D periodic arrays, and such a single 2.5-D periodic layer of via-based structure is demonstrated to produce a highly stable angular response up to 60° for both TE and TM polarizations. By cascading two layers of such 2.5-D periodic arrays, the proposed FSS is able to obtain a broad passband as well as the wide out-of-band rejection. Moreover, it has a quite sharp band edge between the passband and the specified stopband. A corresponding equivalent circuit model (ECM) is further developed for better analysis of the operating principle. Finally, a prototype working at the center frequency of around 28 GHz is fabricated and measured. The main novelty of this paper is introducing the 2.5-D concept into designing a wideband FSS, and further reduce the unit size as well as improve the angular stability. Favorable agreement is achieved among the 3-D full-wave simulation, ECM and measurement. All these results demonstrate that the proposed FSS is a good candidate for 5G EMI shielding.

A 2.5-D Angularly Stable Frequency Selective Surface Using Via-Based Structure for 5G EMI Shielding

A reconfigurable frequency-selective surface (RFSS) for electromagnetic shielding applications is presented in this letter The unit cell of the proposed RFSS contains a pair of shorted square loops separated by a uniform distance Wideband RFSS with the frequency tuning ratio of 1:234 achieved by varying the horizontal spacing is proposed The RFSS covers the frequencies 35, 5, and 58 GHz shielding the WiMAX, WLAN, and ISM/WiMAX bands, respectively The prototype of the proposed RFSS is fabricated and loaded on to the mechanical tuning setup The tuning setup has a box frame with rotating shafts attached to the bevel gears to control the horizontal spacing The use of collapsible linkage mechanism ensures uniform spacing during reconfigurable operation The simulated results are validated with measurements The proposed FSS offers wideband frequency tuning for electromagnetic shielding applications

A Wideband Frequency Tunable FSS for Electromagnetic Shielding Applications

A low-profile broadband bandpass frequency selective surface (FSS) with two rapid band edges is proposed in this paper for 5G near-field applications. The overall structure consists of three metallic layers, separated by two thin substrates with a thickness of 0.07λ. In addition, some centro-symmetric miniaturized slots are introduced in the middle metallic layer to further improve its stability and reduce its physical dimensions. A corresponding equivalent circuit model (ECM) is also proposed to better analyze the principles of the proposed FSS. Finally, an FSS prototype working at the center frequency of 27.5 GHz with a relative -3 dB bandwidth of 20.5% is fabricated and measured. More than 25 dB shielding effectiveness can be obtained out of the passband for a bandwidth of 1.46 GHz in this experiment. Both 3-D full-wave simulations and ECM results are in good agreement with the experimental results, having a maximum deviation of only 2.257% in the transmission zeros and poles. These results demonstrate that the proposed FSS is a good candidate for 5G near-field EMI shielding.

A Low-Profile Broadband Bandpass Frequency Selective Surface With Two Rapid Band Edges for 5G Near-Field Applications

Based on 2.5-dimensional (2.5-D) structure, a novel compact dual-band frequency selective surface for GSM shielding is proposed in this letter. The unit cell geometry is designed by knitting double square-loop elements in 2.5-D which realizes the compact dual band-stop characteristics successfully. The size of proposed 2.5-D frequency selective surfaces (FSS) cell is only 0.072 λ0, where λ0 corresponds to free-space wavelength of the lower resonance frequency. The 2.5-D FSS is modeled and simulated by Microwave CST STUDIO SUITE. The simulation result shows that the FSS offers band-stop response at 900 and 1790 MHz with shielding effectiveness of 41.9 dB and 49.2 dB, respectively. Furthermore, the 2.5-D FSS performs a good angle-stability under both TE and TM polarizations. Hence, the designed 2.5-D FSS can be used for GSM shielding effectively. A prototype of proposed 2.5-D FSS is fabricated. The measurement result proves the satisfactory consistency with the simulation results.

A Novel Compact Dual-Band Frequency Selective Surface for GSM Shielding by Utilizing a 2.5-Dimensional Structure

A low profile dual-band frequency selective surface (FSS) for shielding the GSM applications is presented in this paper. The proposed FSS contains the unit cell made of modified double square loop elements with paper as its substrate. The overall thickness of the proposed FSS measures only 0.55 mm. The FSS offers band stop response at 930 and 1720 MHz with 18 dB shielding effectiveness for a bandwidth of 100 and 173 MHz, respectively, thus shielding the GSM signals. Additionally, the modified double square loop element-based FSS is symmetrical providing the advantage of polarization independency. It also exhibits angular stability up to 60° for both the horizontal polarized electric field (TE mode) and vertically polarized electric field (TM mode). A prototype of the proposed dual-band low profile FSS is fabricated. The simulation results are compared with the experimental results and are found to be in congruence with each other.

Lingeshwaran Murugasamy

Papers

A Low-Profile Paper Substrate-Based Dual-Band FSS for GSM Shielding