Band Frequency Selective Surface Research Articles

Triple band frequency selective surface design for 5G mm‐wave communication with artificial neural networks

AbstractHigh‐performance frequency selective surfaces (FSSs) have gained attention for their spatial filtering characteristics in 5G communication systems. In this work, we propose an efficient and accurate design methodology for the FSS. Three different artificial neural network methods (ANN) are employed, and their performances are compared for analysis and synthesis purposes. Results show that GRNN has the highest performance for both training and test phase of ANN based FSS analysis and synthesis. A novel, compact, low‐profile triple band FSS unit cell is introduced, and the working mechanism is described. By applying ANN based design procedure, the unit cell dimensions to resonate at the 5G mm‐wave frequency band is extracted. A unit cell with the extracted physical dimensions is simulated with a full‐wave analysis tool. The simulation results show that the FSS has the filtering feature at the predetermined mm‐wave frequencies of the 5G communication. The prototype of the FSS is fabricated, as well. The simulations are verified experimentally with measurement results. The results show that proposed ANN based analysis and synthesis method can be an effective tool for the design of FSS band‐pass filter for 5G applications.

Higher Order Bandpass Single and Dual Band Frequency Selective Surfaces With Aperture Coupled Patch Resonators

Higher Order Bandpass Single and Dual Band Frequency Selective Surfaces With Aperture Coupled Patch Resonators

Novel Dual Band Frequency Selective Surface and its Applications on the Gain Improvements of Compact UWB Monopole Antenna

In this work, a highly directional ultra-wideband (UWB) microstrip patch antenna as a single-element is suggested. The proposed antenna’s gain is enhanced with a novel dual-band frequency selective surface (FSS) placed beneath it. The FSS design has a hexagonal structure with meander line inductances and a capacitance-like structure connecting all of the corners to the middle. There is no metallic layer on the other side of the substrate, which shows transmission zeros at 4.95 GHz and 12.7 GHz, and a modified U-shaped monopole antenna is developed. First, the performance characteristics of the antenna and FSS are analyzed from the simulation results, and they are validated experimentally after fabrication, followed by measurement. The compact configuration comprises an antenna loaded with the proposed FSS results S11 less than -10 dB from 3.15 GHz to 22.65 GHz, covering the UWB band together with the X, Ku-band with a bandwidth of 19.5 GHz (151.16% FBW). The antenna’s overall physical dimensions would be 38.8 mm×38.8 mm×25.2 mm (0.407λo×0.407λo×0.265λo), with λo denoting the lowest frequency’s free-space wavelength. The FSS loading results in a 9.9 dBi maximum gain at 10 GHz. The antenna’s small size increases bandwidth, and its high peak gain makes it ideal for use in real-time applications.

Single-layer frequency selective dual-band reflectarray operating at 28 GHz and 39 GHz

We report a single-layer frequency selective dual band reflectarray operated at 28 and 39GHz simultaneously. The reflectarray consists of cross dipole and spiral elements aligned on the surface of a substrate and dual band frequency selective surfaces aligned on the rear side. We aligned the cross dipole and spiral elements that can control the reflection direction at 28 and 39GHz aligned on the same plane of the substrate, resulting in a simultaneous dual-band control of the reflection direction up to ±30° independently. Furthermore, the dual band reflectarray showed higher transmittance at frequencies except for the target frequencies, indicating the reflectarray function only at 28 and 39GHz and does not interfere with the other communication bands.

A tunable frequency selective surface integrated high isolation MIMO antenna for THz applications

A novel tunable triple stop band frequency selective surface (FSS) is designed and integrated with the multiple inputs multiple outputs (MIMO) antenna as an isolation structure to verify its validity. The proposed FSS renders excellent isolation characteristics for the reported MIMO system which is verified from the ECC and DG plot. In FSS, the graphene materials are attached at the end of three stubs to realize tuning over the respective bands. The center frequency of the attained triple bands shows an obvious shift from 2.2 to 2.4 THz, 3.15 to 3.5 THz, and 4.6 to 4.9 THz on increasing the chemical potential of graphene from 0 to 1.5 eV. The tuning range can be enhanced by further increasing the applied potential and hence its service might extend to multi or wideband MIMO systems. The proposed FSS unit cell achieves miniaturization to the level of 0.17 λ o. The validity of the proposed FSS is tested with a linear array MIMO antenna. The designed MIMO antenna consists of two linear array antennas separated by 40 μm with each linear array is made up of three individual antenna elements. The introduction of FSS between the linear arrays provides the minimum isolation of 30 dB. The presented highly isolated linear array MIMO antenna realizes maximum efficiency and gain of 83%, 12.2 dBi respectively. The FSS unit cell structure is modeled and their electromagnetic characteristics are simulated by the 3D electromagnetic simulator CST Studio Suite. The auto meshing technology and frequency domain solver are used to acquire S-parameter. This wearable antenna is a significant component in tracking and monitoring systems including the miniaturized multiband antennas exhibiting stable radiation characteristics during bending, stretching, and crumpling conditions to suit military applications. Nowadays, wearable antennas are being designed for military applications by perfectly matching the industry requirements such as thin, low profile, lightweight, low maintenance, robust, conformal, easy integration into clothing without affecting the movement of the soldier.

Wideband hybrid microstrip patch antenna and gain improvement using frequency selective surface

SummaryA wideband hybrid microstrip patch antenna with high bandwidth dimension ratio (BDR) is reported in this research work. The electrical dimension of the presented antenna is 0.268λ × 0.201λ × 0.01λ, where λ is the maximum operating wavelength of the antenna. The patch consists of one circle and four parallelograms overlapping with each other. The patch looks like a two dimensional “PINE TREE.” The fabricated antenna exhibits return loss less than −10 dB from 2 to 15.40 GHz with a percentage bandwidth of 154% and BDR of 2859. Also a peak gain of 3.3 dBi is achieved at 8 GHz. To improve the peak gain further over the entire frequency band, proposed antenna is combined with a mono layer stop band frequency selective surface (FSS). Without disturbing the original bandwidth, the antenna is mounted on top of 16 unit cell FSS arranged in of 4 × 4 matrix. When FSS is placed at a suitable minimum distance, maximum gain of 7.22 dBi is achieved by the combined structure. Physical dimension of the proposed FSS combined antenna is 64 × 64 × 35.2 mm, which is very much suitable for long range wireless applications. Both the antenna and the FSS are designed and simulated using Computer Simulation Technology (CST) software. Also it is fabricated on FR4 substrate. It has loss tangent (tan theta) of 0.02, dielectric constant of 4.4, and thickness of 1.6 mm. All the simulation results have been validated using Vector Network Analyzer (VNA). The measured results exhibit good compliance with the simulated results.

Miniaturized dual stop band frequency selective surface with broadband linear co to cross polarization conversion ability

This work presents a miniaturized angularly stable frequency selective surface (FSS) on a single layer substrate. Unit cell comprises of convoluted circular rings connected cross dipole and linear arrow headed dipole printed on both sides of the substrate. A closely spaced dual stop band resonances are obtained at 10 and 14.3 GHz with frequency ratio of 1.43. FSS shows a − 10 dB stopband bandwidth (BW) from 7.32 to 11.05 GHz (40.61%) and 12.68 to 15.97 GHz (22.97%) with >30 dB stop band rejection at center frequencies. FSS poses the features of stable performance under change in polarization and angularly stable response up to 60° incident angle. Later the proposed FSS is printed on grounded thick dielectric substrate and it shows broadband reflection type co to cross polarization conversion from 7.2 to 17.32 GHz (82.54%) with polarization conversion ratio >80% and oblique angle stability up to 35°. To the best of authors' knowledge, this is the first time in literature a single unit cell geometry with two different properties, spatial filtering on transmission and polarization conversion on reflection have been designed and analyzed in details. A finite array with size 25 × 25 of the proposed FSS is fabricated and the measured filter response shows a good agreement with simulated performance at normal and oblique incidences. The proposed FSS is used as a reflector of a dual band monopole antenna and the simulation results shows gain improvement of 5.51 and 3.8 dB at the two stopband frequencies.

A Cascaded Tunable Wide Stop Band Frequency Selective Surface with High Roll-off Band Edge

A Cascaded Tunable Wide Stop Band Frequency Selective Surface with High Roll-off Band Edge

Miniature Convoluted FSS for Gain Enhancement of a Multiband Antenna

Convoluted elements on a frequency selective surface (FSS) allow for low frequency elements to be contained in physically smaller unit cells. Smaller unit cells give the FSS greater angular stability, especially where a curved FSS is required, and so unwanted grating effects are avoided. A convoluted element FSS with a frequency rejection band centred at 2 GHz and unit cell area of 15 mm by 15 mm ( $0.10\,\,\lambda \times 0.10\,\,\lambda$ ) has been developed. To test its usefulness, the full structure FSS is used as a parabolic reflector in a dual band FSS reflector antenna operating at 1 GHz and 2 GHz. Simulated and measured results are close at both bands. The reflector antenna has high gain at 2 GHz of 12.7 dBi (simulated) and 11.7 dBi (measured). To observe the angular stability of the FSS and therefore its effectiveness as a reflector, it was compared with a copper test reflector at both bands. Simulation of the reflector antenna with test reflector produced a 2 GHz gain of 13.3 dBi which is very close to that with the FSS reflector. The simulated 2 GHz gain plot of the reflector antenna with FSS reflector is very similar to that with the test reflector indicating that the FSS has good angular stability. The gain at 1 GHz is also high with 9.3 dBi (simulated) and 8.7 dBi (measured). Simulation of the reflector antenna with no FSS and only a rear test reflector produced a 1 GHz gain of 10 dBi which is very close to that with the FSS reflector in place indicating that the FSS causes no significant attenuation at that frequency. The convoluted element FSS would be useful as a curved reflector in the creation of high gain, multiband, conformal antennas.

Miniaturized Angularly Stable Dual Band Frequency Selective Surface for K and Ka Band

A single layer novel compact frequency selective surface which is used in reflector antenna is designed and simulated. The proposed unit cell reflects electromagnetic waves in K and Ka band with maximum reflection occurring at 22.62 GHz and 35.44 GHz respectively. The designed FSS find its application in satellite communication. A crossed dipole structure in center and two-legged structure in corners with square loop in each quadrant makes the FSS unit cell structure. The FSS is designed with oblique incidence for transverse electric and transverse magnetic polarization with return loss 0.3 dB in 22.62 GHz and less than 0.5 dB in 35.44 GHz. The proposed work shows frequency independence against oblique angle of incidence. The simulated result from CST microwave studio is compared with other similar works.

A miniaturized flexible frequency selective surface for dual band response

AbstractIn this paper, a novel miniaturized and flexible dual band frequency selective surface (FSS) is presented. This FSS provides effective shielding in X-band and Ku- band, with a frequency response of 9.4 and 16.7 GHz, respectively. The proposed FSS provides 924 MHz bandwidth at X-band and 1.34 GHz bandwidth at Ku-band with an insertion loss of 20 dB. Moreover, the proposed design is polarization-independent and it provides stable frequency response at various angles of incidences for both transverse electric and transverse magnetic modes. More significantly, the proposed FSS analyzed the bandstop response of the selective frequency and also is suitable for conformal applications. A prototype of the proposed FSS is fabricated. The measured results and simulated results are good in agreement.

Compact Ultra-Wide Band Frequency Selective Surface With High Selectivity

In this communication, an ultra-wide band frequency selective surface (FSS) with excellent transmission performance in the desired passband and reflection performance in the out-of-band is proposed. In order to simultaneously achieve a wide bandwidth, as well as the better band-stop characteristic, a cascaded hybrid resonant element is employed to construct the FSS, which is composed of resonant circular rings and inductive meandering grid arranged on different layers. In addition, a fifth-order equivalent circuit model (ECM) is established over the entire band from 0.1 to 8 GHz, which can accurately describe the frequency responses. Finally, a prototype of the proposed design is fabricated and measured. The results show that a wide −3 dB bandwidth of 154.4% from 0.5 to 3.88 GHz is achieved. The −10 dB stopband is from 4.04 to 7.68 GHz and a sharp transition within 160 MHz from passband to stopband is obtained. The dimensions of the element are as compact as $0.0263\lambda \times 0.0263\lambda $ at the starting frequency of the passband. All the results demonstrate the ultra-wide bandwidth advantage and excellent out-of-band reflection, steep roll-off, and miniaturization performances.

Design and Synthesis of an Ultra Wide Band FSS for mm-Wave Application via General Regression Neural Network and Multiobjective Bat Algorithm

In this work is presented a hybrid bioinspired optimization technique that associates a General Regression Neural Network (GRNN) with the Multiobjective Bat Algorithm (MOBA), for the design and synthesis of the Frequency Selective Surfaces (FSS), aiming its application in data communication systems by diffusion of millimeter waves, specifically, in the IEEE 802.15.3c standard. The designed device consists of planar arrangements of metallizations (patches), diamond-shaped, arranged over a RO4003 substrate. The FSS proposed in this study presents an operation with ultra-wide band characteristics, its patch designed to cover the range of 40.0 GHz at 70.0 GHz, i.e., 30.0 GHz bandwidth and 60.0 GHz resonance. The upper and lower cutoff frequencies, referring to the transmission coefficient’s scattering matrix (dB), were obtained at the cutoff threshold at -10dB, to control the bandwidth of the device.

Single layer miniaturized ultra-thin FSS with five closely spaced bands

AbstractThis Paper reveals a novel single layer five band frequency selective surface (FSS). Novelties of the proposed FSS lie in its five closely spaced stop bands at 2.4, 3.38, 4.82, 6.32, and 7.75 GHz as well as the reduced single layer structural thickness (0.0016 λ0) and the miniaturized unit cell size (0.0656 λ0) at lower resonant frequency as compared to the existing multiband FSS. The unit cell structure consists of six octagonal concentric interconnected loops. Adjacent loop interconnection technique reduces the cell size by more than 44%. Furthermore, arrow-shaped rings are also introduced on each corner of the outermost octagonal loop, and using this technique approximate 23% cell miniaturization can be achieved. In addition, the proposed FSS exhibits excellent angular stability.

Polarization Insensitive Dual Band Frequency Selective Surface for RF Shielding Through Glass Windows

This paper reports on a dual-band, polarization-insensitive frequency-selective surface (FSS) directly realized on window glass for Wi-Fi and WLAN shielding applications. The design incorporates an annular ring and modified flower-shaped geometry to suppress 2.45 and 5.5 GHz bands, respectively, while acting ineffective to the rest of the frequency spectrum. The proposed design is completely insensitive to incoming wave polarization owing to its symmetry. The FSS also offers excellent incident wave angular stability up to 45°. Additionally, a wide rejection bandwidth (−10 dB) of more than 630 and 1430 MHz for lower and higher bands, respectively, is obtained suffice to cover the WLAN spectrum. Unlike conventional screen-printed FSS for glass applications, the conducting patterns of the proposed FSS are realized with copper foil directly laminated and etched on the glass substrate while maintaining 86% transparency for sufficient light passage. The detailed analysis of all parameters has been carried out, and their effect on the performance of FSS is reported. An equivalent lumped circuit model is also generated for the proposed design to better understand the physical phenomena of electromagnetic (EM) wave suppression. A finite prototype containing 13 × 10 elements is fabricated and tested. The measured results are in good agreement with the simulated ones. The FSS offers measured suppression of 43 and 40 dB at 2.45 and 5.5 GHz bands, respectively. The design has excellent potential for EM field suppression, WLAN isolation, and security applications in indoor environments.

High gain dual band slot antenna loaded with frequency selective surface for WLAN/fixed wireless communication

AbstractThis study shows the gain enhancement achieved through dual band slot antenna incorporated with dual band frequency selective surface. In order to do this, at first, a dual band novel 7 × 7 spanner shape FSS is designed, and its operations is analyzed by using the ray tracing method. The second step involves designing the dual band slot antenna resonating at 3.53 and 6.2 GHz, respectively. The designed FSS is then used as superstrate on the slot antenna in which cavity resonance occurs due to multiple reflections and leaked out waves, thereby enhancing antenna's gain significantly on both the bands. Further, the overall gain of slot antenna with the superstrate is achieved as 13.00 and 13.92 dBi on the 2 respective resonant frequencies; this in turn results in a gain enhancement of 8.0 and 6.82 dB at 3.53 and 6.2 GHz, respectively. The measured results coincide verifying the results of the simulated structure. This is followed by a parametric analysis for air gap between FSS and the radiating antennas, which in turn have been designed for wireless and satellite communications.

Dual stop band frequency selective surface for C and WLAN band applications

A miniaturized unit cell design of Frequency Selective Surface (FSS) to produce stop band characteristics for two bands is presented. The presented unit cell structure is showing the band filtering characteristics for dual frequency band specifically C-band for satellite communication and Wireless Local Area Network (WLAN). The designed FSS structure is comprised of I shaped and modified I shaped metallic strips. The distinct unit cells of suggested are investigated for band filtering characteristics and finally integrated on a single unit cell for dual-band filtering applications. The I shaped and modified I shaped unit cell is producing band filtering properties at center frequencies like 4 GHz and 5.5 GHz respectively. The presented FSS design is modeled on an FR-4 substrate with dielectric constant of 4.4 and the dimension of the unit cell is 10 × 10 × 1.6 mm3. The fabricated FSS structure is simulated and measured for its characteristics verification like S11 and S21 and it has been found a satisfactory agreement in simulated and measured results.

Dual band, low profile and compact tunable frequency selective surface with wide tuning range

In this paper, a dual polarized, dual band, low profile, embedded bias network, and compact tunable varactor band pass frequency selective surface (FSS) is designed with a wide tuning range. The proposed FSS is composed of two metallic layers printed on both sides of the substrate, where the top side has two cross strips with different dimensions encircled with high pass grids, whereas the bottom side includes a proper bias network. The loaded varactors between the grids and the cross strips with a designed bias network achieve two independent tunable pass bands. Moreover, an equivalent circuit of the FSS is extracted, which show good agreement with the full wave simulation results. The proposed FSS can operate from 2.28 GHz to 4.66 GHz and from 5.44 GHz to 11.3 GHz by proper tuning of the varactors loaded in the large and small cross strips. The tunable range of the low and high pass bands are about 70% with respect to the center frequency of each pass band. The electrical dimensions of the proposed FSS are about 0.05λ × 0.05λ, where λ is the free space wavelength at a lower pass band (2.28 GHz). Moreover, the proposed FSS works properly up to 60° incident angles.

All‐Dielectric Frequency Selective Surface Based on 3D Printing Materials

In this paper, the authors demonstrate a method of using low permittivity 3D printing materials to design all‐dielectric frequency selective surface (FSS). The 3D printing method can be used to fabricate complex structures rapidly and freely. The relative permittivity of materials used in 3D printing is in the range of ≈2.5–4.5. These low permittivity materials are usually transparent to the electromagnetic (EM) waves. In this paper, these low permittivity materials are used to realize stop band FSS to inspire the localized enhanced electric resonances and magnetic resonances by the periodic design. With the ability of using different dielectric materials with low permittivity, FSS with more functional effects may be designed and fabricated in an inexpensive and bio‐friendly way.

Polarization Insensitive Compact Wide Stop-band Frequency Selective Surface

Abstract A compact, polarization insensitive, wide stop band frequency selective surface is presented. The unit cell is designed by modifying the basic square loop FSS. The simulated value of bandwidth for transmission < ‒ 20 dB for TE incident wave is 7.7 GHz from 4.71 GHz to 12.41 GHz which is 89.95% corresponding to the center frequency of this range. It has an excellent band stop response for C and X band. The periodicity of the unit cell is the order of 0.33λ0 at the center frequency of 8.56 GHz. The total thickness of the proposed structure is 1.6mm (0.045λ0). Standard design formulas are used to evaluate the resonance frequencies and calculated values are found to be very close to the simulated ones. The proposed design is polarization insensitive and has good angular stability. An array of the proposed design is fabricated on either side of dielectric substrate FR4. The measured and simulated transmission responses are in good agreement. Proposed design can be used for many potential applications such as electromagnetic shielding, spatial filtering, sub - reflector in antennas and RCS reduction etc.