Miniaturized Frequency Selective Surface Research Articles

Design of 2.5-D miniaturized frequency selective surface with enhanced oblique stability

This paper presents a miniaturized 2.5-D frequency selective surface (FSS) that exhibits a band stop response at frequency of 1.5 GHz. In the unit cell, the meander patterns on both side of the substrate are connected in series by four vias. Moreover, the meandered pattern in each quadrant is also connected with one of the meander patterns of the adjacent unit cell. In this manner, a 2.5-D closed loop is created with large perimeter. The enlarged perimeter amplifies the effective inductance and leads to a decrease in both the resonant frequency and the dimensions of unit cell. Subsequently, the proposed FSS demonstrates excellent miniaturization with an overall size of 0.038 λ 0 × 0.038 λ 0. Moreover, the frequency response is highly stable up to 86° for both TE and TM polarization. The resonance mechanism of the designed FSS is explicated through distribution of surface current and electric field. The testing board of the proposed FSS has been fabricated for the verification of the design. The measured frequency response of the prototype are congruent with the simulation results. The distinguished features of the constructed structure are enhanced angular stability, miniaturized unit cell, low profile, simple geometry and easy fabrication.

A Single Layer Interdigitated Loop Elements-Based Miniaturized Frequency Selective Surface for WLAN Shielding

A Single Layer Interdigitated Loop Elements-Based Miniaturized Frequency Selective Surface for WLAN Shielding

A Miniaturized Frequency Selective Surface for GSM Shielding by Utilizing a Spiral Handshake Structure

A Miniaturized Frequency Selective Surface for GSM Shielding by Utilizing a Spiral Handshake Structure

Machine Learning Empowered Magnetic Substrate Coupled Broadband and Miniaturized Frequency Selective Surface

This works offers a polarization-insensitive, wide angular stable, and wideband electromagnetic interference shielding structure using an integration of frequency selective surface (FSS) with magnetic substrates. The equivalent circuit model (ECM) together with the analytical model is derived to figure out the physics of the shielding structure. The overall inductance of the shielding structure is increased using a magnetic ferrite sheet and magnetic silicon rubber sheet as substrates. Further, four different deep neural network configurations are investigated with inverse modeling to predict the shielding structure parameters within a fraction of seconds. The mse between expected and predicted output is only 2.92 × <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$10^{-8}$</tex-math></inline-formula> . The entire X-band is shielded with a minimum 10-dB shielding effectiveness (SE) and with SE of 56 dB at resonance. The FSS unit cell size is only 0.21 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda$</tex-math></inline-formula> × 0.21 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda$</tex-math></inline-formula> . Furthermore, the proposed shielding structure shows stable transmission performance up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$75^{\circ}$</tex-math></inline-formula> angle of incidence for both perpendicular and parallel polarization. Finally, a prototype is fabricated and measured using nondestructive free space measurement. Good agreement among the simulated, ECM, analytical model, and measured results demonstrate the efficacy of the proposed technique for building an effective shielding structure.

A novel dual‐band miniaturized frequency selective surface with high selectivity

AbstractIn this paper, a novel dual‐band multilayer frequency selective surface (FSS) with high selectivity and miniaturization characteristics is proposed. The FSS consists of a top and bottom resonant layer and an intermediate coupling layer. The top and bottom resonant layers provide dual‐band passbands, and the cross‐coupling between the three layers makes the structure produce four transmission zeros (TZs) distributed two‐by‐two on both sides of the passband to improve the sharp roll‐off characteristics of the structure. Use bent structures in the top and bottom layers of the cell design to achieve miniaturization of the elements. FSS provides stable performance in incident angles from 0° to 45° with different polarizations of incident waves (TE and TM wave). The lower band of FSS works at 9.1 GHz and the higher band works at 10.26 GHz, the cell size of FSS is , FSS samples were made and tested, and the test results fit well with the simulation results.

Kapur’s entropy based honey badger optimization for design of miniaturized frequency selective surface for 5G electromagnetic shielding

Kapur’s entropy based honey badger optimization for design of miniaturized frequency selective surface for 5G electromagnetic shielding

A New Miniaturized Low-Profile and Stable Dual-Band FSS with 2.5D Structure for ISM Bands

Based on 2.5-Dimensional (2.5D) frequency selective surface (FSS) structures, a new miniaturized frequency selective surface structure is proposed in this work to operate as a bandreject filter in the 2.4 GHz (2400 to 2483.5 MHz) and 5 GHz (5150 to 5350 MHz and 5470 to 5725 MHz) ISM (Industrial, Scientific, and Medical) bands. The FSS has the metallization layer formed by a square loop with an internal cross loop, with each geometry being responsible for a rejection frequency range. The main characteristics of the structure are discussed, emphasizing the resonance frequency variation as a function of the increasing number of vias. Numerical results are obtained through simulations using the commercial software ANSYS HFSS. In addition, by analyzing numerical results for structures with different numbers of vias, it was possible to obtain expressions for calculating the first resonance frequency for each geometry. The cell size of the 2.5D FSS of the proposed cell is only 0.0883 λ0, where λ0 corresponds to the free-space wavelength of the lower resonance frequency. The FSS presents dual polarization, angular stability for angles up to 50° and its simulated response presented two resonant frequencies, the first at 2.65 GHz and the second at 5.34 GHz, with relative bandwidths of 38.11% and 35.96%, respectively. For comparison and validation purposes, the prototype is fabricated and measured. A very good agreement between the simulation and measurement results is observed.

A Dual-Frequency Miniaturized Frequency Selective Surface Structure Suitable for Antenna Stealth

A tiny dual-band frequency selective surface structure is proposed in this paper. With dual-band rejection characteristics at the corresponding frequency points of the S-band and C-band, suitable for antenna stealth. To achieve miniaturization, the unit-cell architecture resembles the shape of a “S.” First of all, the author describes the parameters of the surface element, and then, the transmission characteristics of the surface element are analyzed by the equivalent circuit method. By maintaining a constant response to TE and TM polarization patterns and oblique incident angles, the suggested device ensures angular independence. The measured findings from the constructed FSS are used to validate the computed results. Finally, a new unit structure is provided for the application of FSS in antenna stealth.

A 2.5D miniaturized low-profile ultra-wideband band-stop frequency selective surface

This paper proposes a miniaturized UWB band-stop frequency selection surface based on metalized via technology, aiming at the problem of the large cell size and thick profile of the UWB band-stop frequency selection surface. By studying the principle of miniaturization of 2.5D frequency selective surface, a 2.5D ultra-wideband band-stop miniaturized frequency selective surface with high angular stability and low profile is designed. The simulation and test results show that the designed structure can cover the ultra-wideband frequency range of 2.36 GHz ∼ 11.36 GHz, the −10 dB percentage bandwidth is 161.9%, the unit size is , and the thickness is , where represents the resonance wavelength in free space. The maximum incident angle can reach 60 degrees for TE and TM polarization. Compared with the existing literature, the designed ultra-wideband band-stop miniaturization frequency selection surface miniaturization is better, and the profile is lower.

A Novel Fractal Inspired Iterated Four-Legged Loaded Loop Elements Based 2.5-D Miniaturized Frequency Selective Surface

This letter presents a 2.5-D frequency selective surface (FSS) based on four-legged loaded loop elements of third-order iteration inspired by fractal geometries. This FSS design strives to harness the efficacy of the space-filling property of fractals and an additional degree of freedom associated with the use of metal vias in planar structures to obtain a miniaturized unit cell by enhancing the electrical length altogether. The proposed FSS provides a band-stop response with resonance at 1.056 GHz and demonstrates identical transmission curves for transverse-electric and transverse-magnetic modes of polarization of the incident wave. The unit cell of the proposed FSS achieves a figure-of-merit <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$({{{\rm{\lambda }}_{0}}/{\rm{P}}{\boldsymbol{\ }}}){\rm{\ = \ 29}}$</tex-math></inline-formula> , where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${{\rm{\lambda }}_{0}}$</tex-math></inline-formula> is the free space resonant wavelength and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</i> is the periodicity exhibited by the unit cell, and offers an excellent angular stability up to 75° for oblique incidence. The measured results advocate the real-time shielding effectiveness of the fabricated prototype.

Design of Miniaturized and Polarization-Insensitive Double-Layer Frequency Selective Surface Based on Meander Lines

The work presented in this paper concerns a method for the miniaturized frequency selective surface (FSS) based on the meander lines. A miniaturized dual-bandstop FSS structure based on meander lines with spiral-shape is proposed and simulated. The equivalent circuit and current distributions are introduced to explain the FSS performance. The size of the unit cell is 10 mm, which is about 0.037 wavelength at the first resonant frequency. Simulation results indicate that the proposed FSS has a frequency shift smaller than 1% for different polarizations with an oblique incident angle of 60°. A prototype of the FSS is fabricated and measured. The measurement results show that the FSS is polarization-insensitive and angle-insensitive.

Miniaturized frequency selective surface with high angular stability

Abstract In this paper, a miniaturized bandstop frequency selective surface (FSS) with high angular stability is presented. Each FSS element consists of four sets each consisting eight octagonal concentric interconnected loops. The four sets are connected with each other through outermost octagonal loop. The unit size is miniaturized to 0.066 λ0 at the resonant frequency of 1.79 GHz. The proposed configuration achieves excellent angular stability (only 0.025 GHz resonant frequency deviation is observed upto 83° oblique angles). The working mechanism of FSS is explained with the help of equivalent circuit model (ECM), electric field distribution, and corresponding surface current distribution. A prototype of the designed bandstop FSS is fabricated to verify the simulated frequency response. The experimental results are consistent with the simulation results. Simple geometry, low profile, high angular stability, and compact cell size are prominent features of the proposed structure.

A Miniaturized Quad-Stopband Frequency Selective Surface with Convoluted and Interdigitated Stripe Based on Equivalent Circuit Model Analysis.

This paper presents a miniaturized frequency selective surface (FSS) based on the convoluted and interdigitated stripe with multiple narrow passbands/wide stopbands in the L-/S-/C-/X-/Ku-/K-band. By using the convoluted and interdigitated stripe, the coupling inside is well controlled, so that the spatial efficiency is maximized to provide a high miniaturization. An equivalent circuit model is presented to reveal the working mechanism of the proposed FSS. The proposed structure forms four transmission band rejections of 3 dB in 1–6.65 GHz, 8.35–16.9 GHz, 18.0–24 GHz, and 24.50–27.84 GHz. The size of the unit cell is 0.09λ0 × 0.09λ0, where λ0 is the wavelength of the first resonance frequency. The proposed FSS has a good angle stability and polarization stability in a scanning range up to 60°. For verification, an FSS prototype has been fabricated and measured. The measured results were in agreement with the simulated results. The proposed FSS can be used in practical applications such as radomes, antenna reflectors, and spatial filters.

Design of miniaturized FSS using equivalent circuit model and multi-objective particle swarm optimization

A method for designing miniaturized frequency selective surface (FSS) using equivalent circuit model (ECM) and multi-objective particle swarm optimization (MOPSO) algorithm is proposed in this paper. In the proposed method, ECM describing the desired frequency response is established, and parameters of the ECM are determined using the MOPSO algorithm. Combining the ECM analysis and the MOPSO algorithm, the requirements of desired frequency response can be converted into the constraints of equivalent circuit parameters, which simplifies the optimization process of FSS design. For verification, a single-layer bandstop-bandpass FSS composed of convoluted elements with the unit cell size of 0.073λ 0 × 0.073λ 0 is designed. Simulation results show that the −15 dB bandwidth is from 2.62 to 2.83 GHz, and the −0.5 dB bandwidth is from 3.84 to 5 GHz. Meanwhile, the resonant frequency is stable at different incident angles (up to 80°) under TE and TM polarization. Finally, the proposed FSS prototype is fabricated and measured. The measured results agree well with the simulated ones.

A quasi‐elliptical bandpass frequency selective surface with low‐profile and miniaturization characteristics

A low-profile and miniaturized frequency selective surface (FSS) with dual-polarized bandpass characteristics is proposed in this article. The FSS is a second-order structure with two layers separated by an air spacer, achieving two transmission poles (TPs) and two transmission zeros (TZs) at both sides of the TPs. Using the miniaturized structure, the physical dimension of the element is reduced to 0.09λ × 0.09λ, where λ is the free-space wavelength at the center frequency. Thus, the structure exhibits stable performance with respect to different incident angles. The overall thickness is 0.053λ, which is much thinner than alternative second-order FSSs using the traditional cascading technique. This feature makes it a candidate to be applied in low frequency bands with long wavelengths. In addition, the operating principle of the proposed structure is analyzed by using the equivalent circuit method (ECM) and the surface current distribution is also given. Finally, a prototype is fabricated and measured to validate the simulated results.

A Novel Miniaturized Polarization Independent Band-Stop Frequency Selective Surface

A novel miniaturized frequency selective surface (FSS) with a band-stop response at 1.6 GHz is presented in this letter. The designed FSS comprises convoluted elements connected via plated-through holes, which increases the overall electrical length. The proposed FSS unit cell provides the miniaturization of 0.034 λ0 × 0.034 λ0, where λ0 is the free space wavelength corresponding to the resonant frequency. The drafted FSS is polarization independent and angularly stable for both TE and TM polarizations. A prototype of the FSS is fabricated and its simulated results are validated with measurements.

A new miniaturized frequency selective surface designed for Ku‐band absorption and low‐frequency bandpass

AbstractThis article designs a new miniaturized frequency selective surface (FSS) for Ku‐band absorption and low‐frequency bandpass. The miniaturized frequency selective surface (MFSS) consists of a periodically arranged unit structure, each unit consisting of an upper three‐dimensional absorbing structure and a bottom two‐dimensional FSS. The upper layer is a bent‐closed structure that mainly provides over 90% absorption in the Ku‐band. The underlying structure is a FSS in which it acts as a bandpass filter in the transmission band (2.9‐3.9 GHz). The unit‐cell dimension of the MFSS is 0.091λ0 × 0.091λ0 × 0.054λ0 (λ0 is the free‐space wavelength at the resonant frequency). Due to its small size, MFSS can effectively avoid grating lobes and maintain good angular stability. Finally, the actual measurement verified that the MFSS has good characteristics.

Miniaturised frequency selective surface based on fractal arrays with square slots for enhanced bandwidth

A novel approach is used to miniaturise the array size and broaden the bandwidth (BW) of a multilayer antenna-filter antenna- based frequency selective surface (FSS). Although such FSSs have broadly been investigated for higher frequency selectivity and less thickness, they still own high periodicity and lower BW. The proposed fractal FSS with centre square slots consists of three metallic layers, separated by two dielectric substrates and periodicity of the unit cell is sub-wavelength order (0.2 λ ₒ). Central square slots are added in the external Minkowski fractal patches to increase the capacitive effect whereas fractal slots are etched on the ground placed in the middle for enhanced coupling. It is demonstrated through simulations that proposed design can effectively minimise the element size and enhance the BW. Owing to minuscule array size and symmetric fractal geometry, the presented structure is insensitive to higher incidence angles (up to 30°) for both polarisations. A prototype of the proposed FSS is also fabricated and tested in a microwave anechoic chamber. An equivalent circuit model, full wave simulation and measurement results agree well and demonstrate stable response with 3 dB fractional BW approaching 87.4 and 92%, respectively, at a normal angle of incidence.

Ultrathin and Miniaturized Frequency Selective Surface With Closely Located Dual Resonance

Ultrathin and miniaturized frequency selective surface (FSS) with closely located dual bands is proposed in this letter. The proposed FSS comprises parallel patches and meandering lines that construct parallel LC resonators. Then, two independent passbands can be achieved and adjusted by only changing corresponding structure parameters of the element. Through a catercorner arrangement, the structure avoids the effect introduced by the unnecessary inductance. The proposed FSS resonates at 1.59 and 1.96 GHz with a low resonant frequency ratio of 1.23. The proposed FSS provides a low profile of 0.13 mm and a miniaturized unit cell size as compact as 0 . 042λ × 0 . 042λ. A simplified equivalent circuit model is established, which provides good insight into the operation mechanism. Finally, a prototype of the proposed structure is fabricated and measured. All the results present excellent resonant stability with respect to different polarizations and incident angles up to 60°.

Design of miniaturised‐element FSS based on 2.5‐dimensional closed‐loop Hilbert fractal

A novel miniaturised frequency selective surface (FSS) unit cell is proposed based on the Hilbert fractal and 2.5-dimensional (2.5-D) metallic loop. For the increase of current path, both sides of substrate are used which are connected together by four vias. The dimension of FSS unit cell is obtained as 0.041λ0 × 0.041λ0 at the frequency of 2.47 GHz. The transmission coefficient is insensitive and independent of angle and polarisation of incident wave. A prototype model of the proposed FSS is fabricated and measured for the proof of concept. It is shown that it achieves better miniaturisation relative to the FSS reported in the literature.