Frequency Selective Surface Reflector Research Articles

Performance enhancement of Vivaldi-shaped planar UWB antenna using a single-layer FSS reflector

This work proposes the design of a frequency-selective surface (FSS)-based planar monopole antenna for ultra-wideband (UWB) communication applications. The UWB response is observed by integrating a Vivaldi-shaped slot and by introducing a stepped-like pattern on the bottom edges of the radiating patch, while the back side is composed of a partial ground plane. This configuration results in a broad impedance bandwidth spanning from 3.11 to 20 GHz. For radiation performance enhancement of the proposed antenna, a single-layer UWB FSS reflector is placed beneath the antenna element at an optimized distance. The proposed FSS reflector employs a 3 × 3 array of fractal structure with a unit cell size of 12.25 × 12.25 mm2. The designed FSS reflector exhibits a linear phase response over a frequency range of 3.28 to 14 GHz, with a stop-band transmission coefficient less than -10 dB. The incorporation of the FSS reflector results in an increased gain, elevating it from 1 to 4 dBi at low-band frequencies, while at mid-band frequencies, the gain is increased from 1 to 6 dBi. The structural configuration of the proposed antenna yields directional far-field patterns, making it well-suited for UWB radar applications.

High gain frequency reconfigurable multifunctional antenna for modern wireless and mobile communication systems

This article proposes a novel multifunctional wideband reconfigurable antenna with a frequency selective surface (FSS) reflector to improve gain across all operating bands. Initially, a wideband trapezoidal monopole antenna with a 138% impedance bandwidth (1.53–8.45 GHz) on a FR-4 substrate with a thickness of 0.80 mm and an area of 51 × 56 mm2 was designed. In order to achieve multifunctionality, two inverted L structures with two rectangular slots were introduced at the ground plane. Each slot functions as a filter, producing various resonating bands. To obtain the desired resonating frequency bands, the effective length of the slot was changed by strategically placing RF switching element PIN diodes. The proposed reconfigurable antenna can switch between 10 different frequency bands. To improve the gain of the proposed reconfigurable antenna, a novel FSS reflector with a 5 × 5 array of elements is placed 1.01λ (34.54 mm) below the proposed antenna. The application of the FSS results in a 3–6 dBi improvement in antenna gain, not only for the wideband range, but also for all operating frequency bands. Over the entire operating bandwidth, the radiation efficiency ranges from 93% to 75%. For GPS, RADAR, LTE42/43, WLAN, WiMAX, STM-Link, and UMTS applications, the proposed antenna operates in a wideband state, three single band states, four dual band states, and three tri band states. This work provides more antenna functionality at a lower cost, as well as significantly reduced size and space requirements. The proposed antenna can be easily integrated into portable electronic devices for a variety of wireless applications due to its broad switching capability and unique feasibility.

A Wideband High-Gain Microstrip Array Antenna Integrated with Frequency-Selective Surface for Sub-6 GHz 5G Applications.

This paper presents a wideband and high-gain rectangular microstrip array antenna with a new frequency-selective surface (FSS) designed as a reflector for the sub-6 5G applications. The proposed antenna is designed to meet the US Federal Communications Commission (FCC) standard for 5G in the mid-band (3.5–5 GHz) applications. The designed antenna configuration consists of 1 × 4 rectangular microstrip array antenna with an FSS reflector to produce a semi-stable high radiation gain. The modeled FSS delivered a wide stopband transmission coefficient from 3.3 to 5.6 GHz and promised a linearly declining phase over the mid-band frequencies. An equivalent circuit (EC) model is additionally performed to verify the transmission coefficient of the proposed FSS structure for wideband signal propagation. A low-cost FR-4 substrate material was used to fabricate the antenna prototype. The proposed wideband array antenna with an FSS reflector attained a bandwidth of 2.3 GHz within the operating frequency range of 3.5–5.8 GHz, with a fractional bandwidth of 51.12%. A high gain of 12.4 dBi was obtained at 4.1 GHz with an improvement of 4.4 dBi compared to the antenna alone. The gain variation was only 1.0 dBi during the entire mid-band. The total dimension of the fabricated antenna prototype is 10.32 λo × 4.25 λo ×1.295 λo at a resonance frequency of 4.5 GHz. These results make the presented antenna appropriate for 5G sub-6 GHz applications.

High gain wideband and multi-band on-demand reconfigurable antenna for modern wireless application

AbstractThis paper proposes a wide band and multiband frequency reconfigurable antenna that can operate in the UWB, GSM, GPS, 4G LTE, WLAN, and WiMAX bands. The antenna is made up of a trapezoidal-shaped monopole radiator, which was inspired by a rectangular monopole antenna. The ground plane is modified by embedding T and L-shaped slots to notch the desired operating frequency. The proposed antenna can switch to six different frequencies using RF PIN diodes, making it suitable for modern wireless applications. A multilayer frequency selective surface (FSS) reflector is presented to improve the gain of the proposed reconfigurable antenna. The low-profile design achieved a significant increase in gain while retaining the UWB antenna's excellent impedance bandwidth. Because of the use of the FSS reflector, the antenna's average peak gain has increased from 6 to 10.4 dBi. The proposed antenna has a wide switching capability, which validates its unique feasibility for high-speed multiple Internet of Things applications via a common embedded platform under various applications.

UWB antenna with novel FSS reflector for the enhancement of the gain and bandwidth

AbstractIn this paper, a novel ultra-wide-band antenna backed by a suspended ground for an enhancement of bandwidth and a frequency selective surface (FSS) reflector for the enhancement of gain is proposed in order to meet the specific coverage requirements for broadband applications. The impedance bandwidth of the proposed antenna is 13.4 GHz (1.8–15.2 GHz). To enhance the gain of the antenna, a FSS reflector is employed below the suggested ultra wide-band antenna. A novel FSS, which consists of 5 × 5 array of elements, located at a distance of 1.01 λ (36.14 mm) below the proposed antenna. There is 4–5 dBi improvement in antenna gain after application of the FSS. In order to observe the signal correlation of the proposed antenna, the time domain analysis using similar antennas in face-to-face and side-to-side scenarios has been performed using the EM simulation tool CST-STUDIO. The simulated results of the proposed antenna exhibit good agreement with the experimental results of the prototype model antenna.

Wideband and High Gain Array Antenna for 5G Smart Phone Applications Using Frequency Selective Surface

This work presents an eight element array antenna with single layer frequency selective surface (FSS) to obtain high gain. The eight elements are fed by single port. The FSS consists of 14x6 unit cells with one unit cell size is 5&#x00D7;5 <i>mm</i>² having wideband behavior. The antenna uses Rogers RT Duroid 5880 substrate and giving very wide bandwidth from 20 GHz to 65 GHz, covering mm-wave 5G bands (including 28 GHz, 38 GHz and 60 GHz). The designed FSS is showing stop band transmission characteristics below -10 dB threshold from 25 GHz to 42 GHz and 59 GHz to 61 GHz. The eight element antenna integrated with the FSS reflector, which results an improvement in the gain level from 12 dB to 15 dB at 28 GHz, from 10 dB to 12 dB at 38 GHz, and from 9.5 to 11 dB at 60 GHz. The dimensions of the antenna are 33&#x00D7;27&#x00D7;0.787 <i>mm</i>³. The proposed antenna shows stable gain and directional radiation patterns. The simulation findings are experimentally confirmed, by testing the fabricated prototypes of the proposed antenna system.

A Frequency Selective Surface Loaded UWB Antenna for High Gain Applications

This paper presents the design of wideband and high gain Frequency Selective Surface (FSS) loaded antenna for ultra-wideband (UWB) wireless applications requiring high-gain. The antenna consists of a monopole and an FSS reflector. Initially, a conventional rectangular monopole antenna is modified using slot and stub to achieve wide operational bandwidth and size reduction. This modified antenna shows 50% miniaturization compared to a primary rectangular monopole, having a wide impedance bandwidth of 3.6–11.8 GHz. Afterward, an FSS is constructed by the combination of circular and square ring structures. The FSS array consisting of 8 × 8-unit cells are integrated with the antenna as a reflector to enhance the performance of the proposed miniaturized UWB antenna. The loading of FSS results in an improvement of at least 4 dBi gain in the entire operational bandwidth. Moreover, the antenna's bandwidth is also increased at the lower frequency band due to the presence of the FSS. A prototype of the antenna is fabricated and tested to verify the simulation results. The simulation and measurement results show that the antenna offers a wideband –10 dB impedance bandwidth ranging from 2.55–13 GHz with a stable peak gain of 8.6 dBi and retains the radiation pattern stability.

High Gain of UWB Planar Antenna Utilising FSS Reflector for UWB Applications

In this paper, a high gain and directional coplanar waveguide (CPW)-fed ultra-wideband (UWB) planar antenna with a new frequency selective surface (FSS) unit cells design is proposed for UWB applications. The proposed UWB antenna was designed based on the Mercedes artistic-shaped planar (MAP) antenna. The antenna consisted of a circular ring embedded with three straight legs for antenna impedance bandwidth improvement. The modelled FSS used the integration of a two parallel conductive metallic patch with a circular loop structure. The FSS provided a UWB stopband filter response covering a bandwidth of 10.5 GHz, for frequencies from 2.2 to 12.7 GHz. The proposed FSS had a compact physical dimension of 5 mm × 5 mm × 1.6 mm, with a printed array of 19 × 19 FSS unit cells. The FSS unit cells were printed on only one side of the dielectric FR4 substrate and placed as a sandwich between the antenna and the reflector ground plane. An equivalent circuit configuration (ECC) was used to verify the FSS unit cell structure’s performance. The simulated results indicated that the UWB MAP antenna and FSS reflector provided a fractional bandwidth of 136% and a high gain of 11.5 dB at 8.5 GHz with an acceptable radiation efficiency of 89%. Furthermore, the gain was improved across the operating band and kept between 8.3 and 11.5 dB. The proposed antenna was in good agreement between theoretical and experimental results and offered a wide enough bandwidth for UWB and vehicle applications.

Switchable Polarization-Insensitive Frequency-Selective Surface Reflector/Absorber With Low Profile by Using Magnetic Material

A multifunctional frequency-selective surface reflector (FSSR) is found to be an applicable candidate for the realization of an antenna's radar cross-section reduction in or out of its operating frequency. In this letter, a polarization-selectable in-band switchable FSSR/absorber based on diodes is designed and experimentally demonstrated, which comprises a layer of active frequency-selective surface and a layer of metal-backed frequency-dispersive magnetic material (FDMM). The design realizes the switching functions of broadband absorption band from 3.5 to 12.0 GHz (110% bandwidth) with at least −10 dB reflectivity and a reflection band at 6.2 GHz with two-sided absorption bands (2.2–4.8 GHz, 74.3% bandwidth for the lower absorption band and 7.1–12.9 GHz, 58% bandwidth for the upper absorption band) by manipulating the <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> and <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> states of PIN diodes. Besides, due to the use of FDMM, the thickness of the FSSR is only 0.074 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ_L</i> , making it easy to design the reflective surface of the antenna. A prototype of the proposed FSSR/absorber is fabricated and measured, where reasonable agreement is observed.

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 &lt;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.

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.

Absorptive Coding Metasurface With Ultrawideband Backscattering Reduction

In this letter, a new absorptive coding metasurface with a triple-layer topology is proposed to reduce the backscattering in an ultrawide band by combining absorption and diffusion simultaneously. Two separate layers for the coding metasurface and absorber are designed to primarily reduce the high- and low-frequency backscattering. A high-frequency reflective frequency selective surface is added between the coding metasurface and the absorber, serving as an equivalent ground plane for the coding metasurface and eliminating the adverse influence of the harmonic resonances of the absorber at high frequencies. The proposed absorptive coding metasurface is very robust for absorption and diffusion, resulting in a backscattering reduction over an ultrawide band. To validate the concept, an absorptive coding metasurface with a size of 288 mm × 288 mm is designed. Its unit cell exhibits a copolarized reflection magnitude smaller than -10 dB from 1.55 to 19.2 GHz (corresponding bandwidth ratio (BWR) of 1:12.4) with a thickness of 17.73 mm (about 0.092λL at the lowest operating frequency). Simulated and measured results of the absorptive coding metasurface are in good agreement, and they demonstrate a significant backscattering reduction from 1.85 to 19.2 GHz in comparison with a metallic plane of the same size.

Broadband planar slot antenna using a simple single‐layer FSS stopband

In this study, the authors propose a simple structure of a new broadband planar slot antenna using a wide single-layer frequency selective surface (FSS) stopband. The proposed design is realised in two stages. First, the performances of the FSS unit cells are investigated using the finite element method of high-frequency structure simulator. Besides, the FSS structure considered as a stop-band filter in the bandwidth , is also validated by computer simulation technology microwave studio. Second, this FSS reflector is combined with a miniaturised wideband planar slot antenna . The final proposed combination is also designed, optimised, fabricated and validated by measurements. The obtained results show an operating impedance bandwidth of including the Worldwide interoperability for Microwave Access band, the C band for satellite applications, and the Wireless Local Area Network band. Furthermore, the antenna provides an measured maximum gain. Compared to the same antenna without FSS, a maximum gain enhancement of is achieved by the proposed structure. In addition, the back lobes are reduced in the proposed structure by , compared to a simple antenna. The total size of the proposed antenna, integrating the FSS, is .

Compact Size and High Gain of CPW-fed UWB Strawberry Artistic shaped Printed Monopole Antennas using FSS Single Layer Reflector

This study proposed the use of coplanar waveguide Ultrawide-band strawberry artistic shaped printed monopole (SAPM) antenna with a single-layer frequency selective surface (FSS) as the metallic plate to improve the gain of antenna application. The intersection of six cylinders is used to structure the strawberry artistic shaped radiating element, which leads to enhancing the antenna bandwidth. The proposed FSS reflectors used a $10\times10$ array with the unit cell of 6mm $\times6$ mm in introducing a center-operating frequency. This study used the FR4 substrate with coplanar waveguide (CPW) fed to print the proposed antenna, which provided a wide impedance bandwidth of 8.85 GHz (3.05–11.9GHz) that covers the licensed Ultrawide-band. The proposed FSS transmitted a stop-band transmission coefficient, which is below −10 dB with the linear reflection phase over the bandwidth in the range from 3.05 GHz to 11.9 GHz. The UWB SAPM antenna with FSS reflector showed an improvement from 1.65 dB to 7.87 dB in the lower band and 6.3 dB to 9.68 dB in the upper band with an enhancement of 6.22 dB. The gain value is enhanced by the gaping between the antenna and FSS, which has an approximately constant gain response through the band, the gain is sustained among 7.87 dB to 9.68 dB. The total dimension of the antenna is 61mm $\times 61$ mm $\times 1.6$ mm. The proposed antenna structure provides the directional and balanced far-field pattern, which is suitable for Ultrawide-band (UWB) applications and ground-penetrating radar (GPR) applications.

Low Cross-Polarization Improved-Gain Rectangular Patch Antenna

In this paper, a low cross-polarization improved-gain rectangular patch antenna is presented. A patch-ground shorting pin with defected patch structure (DPS) is introduced to suppress the cross-polarization level. A High Reflective Frequency Selective Surface (HRFSS) superstrate is designed and placed over the proposed antenna at an optimized position to intensify the gain. To characterize the unit-cell of the superstrate, its transmission characteristics are extracted and discussed. Integration of the superstrate achieves a beam contraction resulting in a gain enhancement to 10.65 dBi. The proposed antenna has perfect broadside radiation with a cross-polarization level of below −30 dB in the entire half power beamwidth. The prototype of the antenna exhibits good agreement between experimental and simulated results.

Enhancement of transmission characteristics for the antenna system printed on silicon wafer substrate by using FSS‐based coplanar parallel reflector

Here, a silicon-substrate-based four element antenna system is investigated by using a coplanar frequency selective surface (FSS) as a novel parallel reflector to improve radiation and transmission characteristics of the antennas. The four antennas are arranged around the square FSS, and one of the antennas is used as the transmitting element, while the other three as the receiving ones. It is found that, owing to the stopband filtering and the linearly changing reflection phase of the designed coplanar FSS, the gain and directivity of the transmitting antenna have been greatly improved, and that the antenna system transmission coefficients, including S 21, S 31 and S 41, have been significantly increased. Two types of the antenna systems have been designed and fabricated on a P-type silicon wafer substrate for the cases with and without a coplanar FSS reflector. The measured S-parameters are essentially consistent with those simulated. In comparison with the case without the FSS, the transmission coefficients of S 21, S 31 and S 41 for the system with the FSS have been increased about 6.42, 5.97 and 5.89 dB at the center frequency of 5.42 GHz, respectively. Furthermore, the proposed coplanar FSS exhibits distinct advantage of low-profile compared to the conventional vertical FSS reflector.

Compact UWB FSS reflector for antenna gain enhancement

In this study, two compact ultra-wideband (UWB) frequency selective surface (FSS) reflectors, which combine the branch loading method with the design of the traditional FSS, are proposed for antenna gain enhancement application. The working mechanism of the proposed FSS reflectors is analysed by the equivalent circuit model. The first FSS reflector, which is a 10 × 10 array with 8.25 mm × 8.25 mm unit size, not only enhances the gain of the UWB antenna, but also guarantees a constant gain with only 0.5 dB variation across the whole operation band. To further reduce the reflector size, a more compact FSS reflector with 6.25 mm × 6.25 mm unit size is designed by printing similar patterns on both sides of a single-layer dielectric slab. Compared to the first structure, the second reflector can realise a 25% size reduction and the same gain variation in the entire UWB frequency range. The only compromise is a 0.5 dB gain decrease. Finally, a good agreement between the measured and simulated results proves the feasibility of the authors' design.

A WIDEBAND FREQUENCY SELECTIVE SURFACE REFLECTOR FOR 4G/X-BAND/KU-BAND

A Frequency Selective Surface (FSS) reflector with wideband response for 4G/X-band/Ku-band is proposed. The wideband FSS reflector consists of cascaded dual-layer patch FSS which is etched on separ ...

High Gain and Wideband High Dense Dielectric Patch Antenna Using FSS Superstrate for Millimeter-Wave Applications

Gain and bandwidth enhancement of low profile, linearly polarized square dense dielectric patch antennas using a frequency selective surface (FSS) superstrate layer is proposed. A high dense dielectric patch antenna is utilized as a radiating element instead of a metallic patch in order to gain several significant advantages, including low profile, wide bandwidth, and high radiation efficiency. The implemented antenna is excited by an aperture-coupled feeding technique. The antenna gain is enhanced by using a highly reflective FSS superstrate layer, realizing an antenna gain enhancement of 11 dBi. The implemented antenna acquired a measured gain of about 17.78 dBi at 28 GHz with a 9% bandwidth and radiation efficiency of 90%. The bandwidth of the proposed antenna is improved by using a unit cell printed on two sides, as it provides a positive phase gradient over the desired frequency range. The antenna impedance bandwidth is broadened and the measured impedance matching $S{11}$ exhibited a 15.54% instead of 9% bandwidth while maintaining a high-gain characteristic of about 15.4 dBi. The implemented antenna presents a solid radiation performance with good agreement between the measured and simulation results. For some attractive advantages such as low profile, low cost, lightweight, small size, and ease of implementation, the proposed antenna is a very good candidate for millimeter-wave wireless communications.

Performance Enhancement of a Dual-Band Monopole Antenna by Using a Frequency-Selective Surface-Based Corner Reflector

In this paper, we enhance the performance of a dual-band wire monopole antenna operating at 3 and 5.5 GHz by using a frequency-selective surface (FSS)-based corner reflector. In the proposed design, two reflective FSS screens resonating at 5.5 GHz are placed at an angle of 90° and kept at a specific distance from the antenna. The reflector improves the impedance bandwidth (−10 dB) of the antenna from 20% to 44%, as well as its gain, thereby leading to more directive radiation at 5.5 GHz while maintaining omnidirectional radiation at around 3 GHz. A theoretical study is carried out and presented to estimate the enhancement in the electric field of the composite structure in the desired frequency band compared with the absence of a corner reflector in far field. A significant improvement of 8–10 dBi in antenna gain is achieved over 4.5–6.5 GHz; this is maintained at around 12.5 dBi, with a variation of ±1.5 dBi. Experimental measurements are provided in each case. The proposed design can be used as an omnidirectional radiator at around 3 GHz and as a high-gain directional radiator in the 4.5–6.5-GHz band.