Design Of Frequency Selective Surface Research Articles

Narrow Bandpass Frequency Selective Surface With High Level of Angular Stability at Ka-Band

In this letter, a novel design of a narrow bandpass frequency selective surface (FSS) based on the utilization of the coupled method, which resonates at Ka-band frequencies between 29 and 30.3 GHz, is proposed and experimentally evaluated. A high selectivity was achieved, by coupling two metallic layers, which were based on the structure of a cross aperture and a rectangle grid patch, respectively. The simple symmetric patterns used in the proposed work have also made the FSS independent of polarization properties. Moreover, a high angular stability was also achieved since for electromagnetic (EM) wave incident at degrees from 0° to 75°, the frequency deviations were only 0.1% and 0.4% for TE and TM polarizations, respectively. For performance evaluation, an experimental FSS prototype was fabricated by a double-sided printed circuit board (PCB), which was composed of 50×50 unit cells in a dimension of 18 cm ×18 cm. A Keysight N5227A PNA and two-horn antennas in a chamber were setup to measure the performance. The experimental measurement results have shown a good agreement with the numerical simulations.

Design of a Single-Layer Frequency Selective Surface for 5G Shielding

In this letter, a single-layer bandpass frequency selective surface (FSS) working at 2.6 GHz is proposed to decrease the interference to communication systems and the cost of processing based on a multimode resonator. A metasurface unit cell is adopted to suppress the grating lobe and achieve miniaturization. Therefore, the performance of the proposed FSS can remain stable under a large oblique incidence. The surface current distribution and equivalent circuit model at each design step are extracted to explain its working principle. Good agreement between the experimental results and the simulated response verifies the feasibility of the proposed FSS.

Angle and polarization-independent miniaturized UWB FSS design

AbstractA single-layer ultra-wideband (UWB) stop-band frequency selective surface (FSS) has several advantages in wireless systems, including a simple design, low debugging complexity, and an appropriate thickness. This study proposes a miniaturized UWB stop-band FSS design. The proposed FSS structure consists of a square-loop and metalized vias that are arranged on a single layer substrate; it has an excellent angle and polarization-independent characteristics. At an incident angle of 60°, the polarization response frequencies of the transverse electric and magnetic modes only shifted by 0.003 f0 and 0.007 f0, respectively. The equivalent circuit models of the square-loop and metallized vias structure are analysed and the accuracy of the calculation is evaluated by comparing the electromagnetic simulation. The 20 × 20 array constitutes an FSS reflector with a unit size of 4.2 mm × 4.2 mm (less than one-twentieth of the wavelength of 3 GHz), which realizes an UWB quasi-constant gain enhancement (in-band flatness is <0.5 dB). Finally, the simulation results were verified through sample processing and measurement; consistent results were obtained. The FSS miniaturization design method proposed in this study could be applied to the design of passband FSS (complementary structure), antennas and filters, among other applications.

FSS superstrate antenna for satellite cynosure on IoT to combat COVID-19 pandemic

The global pandemic, COVID-19 needs joint techniques and technology to combat it. The internet of things (IoT) has been at the forefront in solving problems, not only in the health care sector but in other sectors. It delivers accuracy with robustness in the developing service and application. However, it remains clear that the use of IoT is limited to coverage, longevity, security, connectivity issue, immediacy, and multicasting, we proposed in this paper frequency selective surface (FSS) as superstrate for rectangular microstrip antenna. An FSS design combine with the rectangular microstrip antenna for better performance is placed over FSS parallel configuration. The rectangular microstrip antenna was titled 45 degrees to change the band-stop. Analysis of the proposed performance in terms of gain, return loss, and directivity shows that the FSS structure's integration brings better results. With the help of a 3D electromagnetic computer simulation technology CST studio suite, we model the proposed antenna, perform the simulation with a frequency-domain solver, and validate it with a time-domain solver. The proposed impressive result is suitable for satellite networks, which hybrid with IoT can provide a sustainable long-time solution in fighting the COVID-19 pandemic.

Comparison of Basic Frequency Selective Surface Design Methods for Optical Windows

Methods for designing frequency selective surface for optical windows are analyzed and experimentally verified. Four methods; ITO coatings, graphene, metallic nano-coatings and metallic meshes; are compared in terms of optical transmission and shielding effectiveness (SE) characteristics. ITO is the most common method for increasing SE performance in the visible band. However, in the infrared band, transmission of ITO is limited. Metallic nano-coating is an alternative for ITO with underperformance from the SE and optical transmission point. Graphene is an emerging method and needs further development. SE performance of the graphene prevents it from being a single material for shielding applications. On the other hand, it might be involved in applications where back reflection is critical because of the electromagnetic absorption characteristic. Metallic mesh is a successful candidate for applications requiring high level SE and optical transmission. However, dielectric properties of substrate the mesh applied, and diffraction effects should be carefully analyzed.

Design Optimization of Origami-Tunable Frequency Selective Surfaces

Recent studies demonstrate the benefit of integrating origami in many engineering applications, where computational methods facilitate the origami design process. An emerging concept utilizes origami design for physically and functionally flexible electromagnetic devices. However, coupled mechanical and electromagnetic design tools are needed to systematically navigate the complex spaces of fold topology and electromagnetic performance. In this article, we introduce topology optimization formulations that find origami fold-driven frequency selective surface designs possessing electromagnetic filtering properties at target frequencies. These formulations utilize a nonlinear mechanics analysis to simulate an origami folding process. A geometric mapping relates mechanically-relevant origami substrate properties and electromagnetically-relevant conductive element properties. Both gradient-based and genetic algorithm methods are used to find optimal origami crease patterns and folded configurations by optimizing fold stiffness and force distributions over a prescribed potential fold line network. Using nonlinear manifold learning techniques, we demonstrate the isolated nature of optimal design candidates in the design space and the complex interplay of fold topology and fold path selection through initial perturbation from the flat state. Collectively, this study provides an initial framework to design novel EM origami structures and also provides important insights on the complex nature of the design space, which can be leveraged to refine future tool development.

Design of frequency selective surface comprising of dipoles using artificial neural network

<span>This paper depicts the design of Frequency Selective Surface (FSS) comprising of dipoles using Artificial Neural Network (ANN). It has been observed that with the change of the dimensions and periodicity of FSS, the resonating frequency of the FSS changes. This change in resonating frequency has been studied and investigated using simulation software. The simulated data were used to train the proposed ANN models. The trained ANN models are found to predict the FSS characteristics precisely with negligible error. Compared to traditional EM simulation softwares (like ANSOFT Designer), the proposed technique using ANN models is found to significantly reduce the FSS design complexity and computational time. The FSS simulations were made using ANSOFT Designer v2 software and the neural network was designed using MATLAB software.</span>

Frequency Selective Surface With Quasi-Elliptic Bandpass Response Using Radiation Null of Patch Antenna

A novel design of bandpass frequency selective surface (FSS) with high selectivity is proposed based on the antenna-filter-antenna (AFA) concept. Traditional AFA-based FSSs improve filtering performance by adding the order of resonator or the coupling paths. On account of the reciprocity theorem, transmission zeros are here introduced by the antenna's radiation null. The proposed FSS consists of two patch antennas connected with one pin and a C-type slot on the ground. The aforementioned structure generates two controllable radiation nulls related to the lengths of slots without any extra circuits. Therefore, two transmission zeros at both edges of the passband can be controlled by adjusting the dimension of slots. A prototype is fabricated and measured. Numerical simulation and measured results are in good agreement, which demonstrates that the proposed AFA-based FSS exhibits a quasi-elliptic bandpass response and a low profile.

A novel design of ultra-wide stop-band single-layer frequency selective surface using square-loop and cross

AbstractIn this paper, a novel design of ultra-wide stop-band single-side single-layer frequency selective surface (FSS) is presented. The unit cell of the proposed FSS is designed using the combination of conventional square loop and cross (CSLC). To enhance the bandwidth of this structure, an additional cross is inserted in all the four quadrants of CSLC. The stop-band transmission bandwidth assuming −10 dB threshold is found to be 128.94% (2.16–10 GHz) which is 34.33% more as compared to the bandwidth of CSLC. The unit cell with a dimension of 16 × 16 mm2 is printed on one side of an FR4 substrate. The design is fabricated and the measured results are found to be in good agreement with the simulated results. The design provides excellent stability for both transverse magnetic and transverse electric polarizations. The design is very flexible, where any resonant frequency can be achieved by changing the length of unit cell. The design is useful in many applications such as antenna gain enhancement, electromagnetic wave shielding for Wi-Fi/5G systems, and other Internet of Things-based applications.

Development of an Analytical Approach to Design FSS Absorber as per User Requirement

An enormous literature is available for the development of electromagnetic (EM) wave absorbers using dielectric materials and frequency selective surfaces (FSS). The prevalent approach of designing the EM wave absorber requires a significant amount of time and resources. In this paper, we have illustrated an approach to design user-defined EM wave absorber impregnated with a simple cross-dipole FSS structure. The proposed model is based on the equivalent circuit modeling and has been validated using the full-wave simulation results. The paper presents a proof of concept demonstrating the efficient designing technique without the use of trial and error methods and with minimum computational and time complexity. The concept shows that the model produces a simple structure and accomplishes the goals set by the user. In the future, fabrication of the absorber sheet will be carried out to validate the proposed approach.

Thermally Tunable Frequency‐Selective Surface Based on VO2 Thin Film

An approach to a design of tunable frequency‐selective surfaces (FSSs) for radio frequency (RF) domain based on vanadium dioxide (VO2) thin films is proposed. As an example, a thermally tunable annular slot FSS with integrated VO2 switchable elements for C‐band of the RF domain is described. Switching is based on abrupt change of conductivity of the VO2 film, initiated by heating from room temperature to a temperature of the metal–insulator phase transition of 44 °C. A tuning mechanism of the FSS allows continuous change of frequency response from room temperature state, where the FSS acts as a band‐pass filter, to high‐temperature state, where the FSS works as a reflector. In the process of tuning, a reflection coefficient at a central frequency of the filter can be increased from −26.4 dB up to −2.2 dB. The proposed approach can be used for the design of tunable FSS for applications that allow thermal control of the frequency response.

Guest Editorial: Non‐Destructive Testing

Guest Editorial: Non‐Destructive Testing

Transforming single-band static FSS to dual-band dynamic FSS using origami

Frequency selective surfaces (FSSs) have been used to control and shape electromagnetic waves. Previous design approaches use complex geometries that are challenging to implement. With the purpose to transform electromagnetic waves, we morph the shapes of FSS designs based on origami patterns to attain new degrees of freedom and achieve enhanced electromagnetic performance. Specifically, using origami patterns with strongly coupled electromagnetic resonators, we transform a single-band FSS to a dual-band FSS. We explain this transformation by showing that both symmetric and anti-symmetric modes are excited due to the strong coupling and suitable orientation of the elements. Also, our origami FSS can fold/unfold thereby tuning (i.e., reconfiguring) its dual-band performance. Therefore, the proposed FSS is a dynamic reconfigurable electromagnetic structure whereas traditional FSSs are static and cannot change their performance.

Design of 3-D FSS with high selectivity based on ELC resonators and spoof-SPPs

The paper proposes a simple band stop frequency selective surface (FSS) design method based on spoof surface plasmon polaritons (spoof-SPPs). The novel FSS design is obtained by combing three-dimension (3-D) FSS and ultra-thin periodic corrugated metallic strip which supports spoof-SPPs. By placing electric-LC (ELC) resonators on the FSS surface at the bottom centre of the corrugated strip, the tight coupling occurs and we show that the SPP modes are rejected near the resonance frequencies of ELC resonators. The steep roll-off at both sides of the stopband can be demonstrated by the ELC resonators, which can find potential applications in wideband antenna radome. In addition, the 3-D FSS shows relatively stable performance with different oblique incidence angles.

Simultaneous Control of Absorbing Frequency and Amplitude Using Graphene Capacitor and Active Frequency-Selective Surface

In this communication, we propose a tunable radar absorber based on the combination of a graphene capacitor with a varactor-loaded active frequency-selective surface (FSS). The absorbing amplitude and frequency can be independently controlled by changing the effective sheet resistance of graphene and the capacitance of the varactor through different bias voltages, respectively. We fabricated the designed absorber and measured its tunable reflectivity. The measured results indicate that the absorber can tune its absorbing frequency ranging from 3.53 to 7.05 GHz under normal incidence when changing bias voltages applied to the varactors from 0.5 to 10 V. By further varying the graphene resistance through the bias voltage, the absorbing amplitude at each absorbing frequency can be dynamically modulated. In addition, it is found that the absorber achieves polarization-insensitive characteristics due to the symmetrical design of the active FSS. The physical mechanism of this absorber is discussed by providing the equivalent transmission-line (TL) model.

Microwave non‐destructive testing of active frequency selective surface embedded tunable radar absorber

The development and performance evaluation of a thin, broadband, and tunable radar wave absorber with reduced complexity is a strenuous task. This Letter reports the design, fabrication, and non-destructive measurement of an active frequency selective surface (FSS) embedded tunable radar absorber. The proposed absorber design consists of periodically patterned, PIN diode mounted-active transmissive/reflective FSS with a straightforward bias network. The tunable absorption characteristics are obtained over a wide frequency range by controlling the bias voltage of PIN diodes. The features of the proposed tunable absorber are demonstrated through non-destructive free space, microwave measurement of a fabricated prototype. The measurement results show the achievement of a remarkable bandwidth of 3.0 GHz, which enables dynamic control of the absorption characteristics ranging from 8.2 to 12.4 GHz. Such an approach paves the way toward the realisation of smart materials and structures for electromagnetic wave manipulation.

Mechanically Reconfigurable Frequency Selective Surface for RF Shielding in Indoor Wireless Environment

A novel polarization-independent reconfigurable frequency selective surface (FSS) for RF shielding is proposed in this letter. The FSS is designed on a flexible and transparent polyester film for shielding Wi-Fi frequency. The symmetrical cross dumbbell design of FSS helps in achieving alike bandstop response for both TE and TM modes with wider angular stability up to 60°. A finite prototype containing 15 × 11 elements is fabricated and tested. The FSS provides the measured shielding effectiveness of 32 dB at 5.2 GHz. Additionally, for RF shielding in an indoor wireless environment, Venetian blind inspired shutter mechanism is introduced in the designed FSS array. By rotating the blinds of the array, frequency tuning is achieved.

Design of a Compact Bandstop Ulam Spiral Frequency Selective Surface

Design of a Compact Bandstop Ulam Spiral Frequency Selective Surface

Dual-Band Frequency Selective Surface Based on Shunted SIW Cavity Technology

The design of a hybrid frequency selective surface (FSS) is presented based on the substrate integrated waveguide cavity (SIWC) technology. The intended design combines two FSS slots (multiapertures) based on the SIWC by sharing the adjacent vias of the unit cell to exhibit unique features in terms of their cavity designs and performance. The design consists of a circular slot with a circular cavity (named as Cavity-A) and a cross slot with a shared cavity with an adjacent unit cell (named as Cavity-B). As a result, the structure shows the dual-bandpass response with sharp roll-off performance characteristics. One band possesses narrowband characteristics at 8.12 GHz. Whereas, the next band with wide bandpass characteristics from 9.5 to 11.5 GHz. Further, the structure has shown a very low insertion loss (IL) of better than 0.15 dB in its operating bands. For proving the concept, a physical prototype has been fabricated, and its functionality verified. A good agreement has been found between the estimated and experimental results.

A 3-D printed square loop frequency selective surface for harmonic radar applications

This paper presents a 3-D printed frequency selective surface (FSS) for harmonic radar applications. The proposed FSS design consists of a square loop printed on the cost-effective acrylonitrile butadiene styrene (ABS) plastic material to pass the signals at 5 GHz resonant frequency band. The proposed FSS is tested for various oblique angles up to 45° and even for different polarization modes. A prototype of the proposed design FSS is fabricated. The results demonstrate a good agreement of simulated results with experimental ones. The 3-D printing technique provides a simple and low-cost method to fabricate FSS and make it suitable for future FSS mass production.