Frequency Selective Surface Superstrate Research Articles

FSS superstrate loaded SIW circular cavity-backed cross-shaped slot antenna for wireless applications

In this paper, a low profile circular-shaped cavity-backed substrate integrated waveguide (SIW) antenna is designed and fabricated to operate at 5.38 GHz frequency in the U-NII-2B band in the dominant TM010 mode. A narrow cross-shaped slot is inserted in the ground plane of the parent antenna for radiation purposes. The antenna produces a gain of 4.7 dBi with an impedance bandwidth extending from 5.36–5.42 GHz. The gain of the antenna is augmented to 7.1 dBi through the use of a multi-layered cascaded frequency selective surface (FSS) as a superstrate. Arlon substrate materials are used to fabricate the antenna and frequency selective surface respectively. Parametric studies have been carried out in terms of return loss, antenna gain, and spacing between the antenna and FSS layer to obtain the best antenna results. All the simulation results have been carried out using HFSS v19.0. Both the simulated and the experimentally measured results show alike behavior.

Performance evaluation of compact FSS‐integrated flexible monopole antenna for body area communication applications

SummaryThis article presents a compact wearable antenna integrated with a novel frequency selective surface (FSS) made of textile materials. The antenna can be applied in wearable health monitoring applications aimed at the 2.45‐GHz Industrial Scientific and Medical (ISM) band. An array of 4 × 4 octagonal slot‐shaped FSS (106 × 106 mm2) superstrate enhances the performance of the modified Koch curve planar monopole antenna (44.85 × 39 mm2). The Jeans substrate prototype with the overall dimensions of 1.128λ0 × 1.128λ0 × 0.319λ0 covers the bandwidth of 2.45‐GHz ISM band from 2.24 to 2.76 GHz (S11 ≤ −10 dB). The band rejection and reflective nature of the proposed FSS suppress the back radiation and improves the antenna's gain by −20 dB and 6.3 dBi, respectively. The specific absorption rate (SAR) level is reduced to 0.445 W/kg from 24.995 W/kg with a higher reduction rate of 98.21%. Many literature reports produced higher gain and lower SAR but exhibited reduced efficiency when the antenna is placed near the human body. The wearable antenna's frequency response tends to vary under bending conditions for narrowband antennas. Wide‐band monopole antennas produce omnidirectional radiation pattern which tends to affect human body tissues. So stable polarization‐insensitive FSS is placed behind the antenna to enhance the antenna's gain and avoid back radiation. The proposed antenna exhibits stable performance under bending conditions with fractional bandwidth of 22.2%, gain of 8.83 dBi, and produces a better efficiency of 91.30% when the antenna is positioned in the vicinity with human body models. The experimental validation shows that the proposed antenna is a promising candidate for wireless body area networks.

An ultrawide‐angle scanning tightly coupled dipole array with double‐layer double‐sided frequency selective surface superstrate

In this article, we present an ultrawide-angle scanning tightly coupled dipole array (TCDA). The impedance match issue is a major challenge in the design of ultrawide-angle scanning TCDA. To overcome this issue, we employ a multi-stage wideband balun and design the balun synergistically with the dipole element to improve impedance match performance. A double-layer double-sided (DLDS) superstrate is exploited to further improve scanning performance in the H plane. The capacitance of the DLDS Frequency Selective Surface (FSS) superstrate is used to counteract the inductance at the upper face of the antenna array to improve impedance match at different scanning angles. The DLDS FSS superstrate has similar performance with the equivalent double-layer dielectric superstrate, but with advantages of light weight, low cost, and low cross-polarization level at high frequencies. Consequently, the proposed TCDA has a bandwidth of 2.4:1 (2.1–5 GHz) with VSWR<3, while scanning up to 80° in the E plane, 70° in the H plane, and 75° in the D plane, respectively. A 16 × 16 prototype was fabricated and measured, showing good agreement with the simulated results.

High gain and wideband circularly polarized S‐shaped patch antenna with reactive impedance surface and frequency‐selective surface configuration for Wi‐Fi and Wi‐Max applications

In this paper, broadband circularly polarized S-shaped patch antenna is designed with a reactive impedance surface (RIS). Besides the RIS structure, the frequency-selective surface (FSS) superstrate is deployed to enrich the antenna gain. The S-shaped patch is modeled on an FR4 glass epoxy and its feed position is set to resonate at 5.3 GHz. The 6 × 6 array size of square patches forms the RIS structure which is inserted in the middle of the S-shaped patch and ground plane to enhance −10 dB impedance bandwidth and 3 dB axial ratio bandwidth. The 6 × 6 array of unit cells forms the FSS superstrate which is deployed approximately half-wavelength (≈λ/2) height above the ground plane to act like a Fabry Perot cavity (FPC) resonator antenna for improving the antenna gain. The combination of RIS and FSS with an S-shaped patch antenna improves the −10 dB impedance bandwidth, 3 dB axial ratio bandwidth, and the gain simultaneously. The proposed antenna resonates over a wide frequency range with a −10 dB impedance bandwidth of 31.8% (4.81–6.63 GHz) and the antenna has a good 3 dB axial ratio bandwidth of 18.9% (4.99–6.03 GHz). The antenna peak gain is around 10 dBi. The proposed antenna prototype is measured in the anechoic chamber and the measured results mimic the simulation results.

Gain augmentation of a dual‐band dielectric resonator antenna with frequency selective surface superstrate

Gain augmentation of a dual-band antenna with different bandwidths using superstrate is presented in this paper. Initially, the dual-band radiator is designed using a rectangular dielectric resonator (DR). The fundamental mode TE111 of the rectangular DR resonates at 3 GHz over a narrowband (BW = 5.08%). The upper wideband (BW = 20% with center frequency 5.86 GHz) is obtained by the amalgamation of two hybrid modes with higher-order TE113 mode. The dielectric waveguide model is used for the theoretical analysis of two radiating modes of the rectangular DR. Further, a dual-band frequency selective surface with bandpass response is designed and loaded as a superstrate above the DR antenna for gain improvement in both the bands, which leads to a gain augmentation of 1.8 dBi and upto 3.5 dBi in the lower and upper band respectively. At last, the proposed design is implemented practically, and measurement results are portrayed to compare with simulation results that agree reasonably well.

A Fabry-Perot Cavity Antenna With Non-Uniform Superstrate and EBG Ground for High Gain and High Aperture Efficiency

A design of high-gain Fabry-Perot cavity (FPC) antenna is presented with non-uniform frequency selective surface (FSS) superstrate and electromagnetic band gap (EBG) reflecting ground. The non-uniform FSS superstrate and EBG ground are utilized to flexibly control the attenuation constant <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> over a large antenna aperture while ensuring the resonance condition of the FPC. The uniformity of the amplitude of the aperture field is improved significantly while obtaining appropriate radiation efficiency. Therefore, the high gain and high aperture efficiency can be achieved within a desirable bandwidth. The theoretical gain estimation is conducted to prove the superiority of the proposed antenna over a referenced uniform one. A straight-forward design methodology is proposed based on the radial leaky-wave theory and the modified transverse equivalent network (TEN) model. The non-uniform high-gain FPC antenna with a diameter of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$6.6\lambda _{0}$ </tex-math></inline-formula> is designed at the frequency of 15 GHz. Simulated results show that a gain of 24.6 dBi with an aperture efficiency of 67.9% has been achieved. The measured gain is 24.0 dBi with an aperture efficiency of 58.4%. The 10dB return loss bandwidth and 3 dB gain bandwidth are 5.3% and 3.2%, respectively. The proposed antenna overcomes the limit on aperture efficiency and gain of conventional uniform FPC antennas, and the presented methodology can guide the design of two-dimensional non-uniform high-gain FPC antennas.

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.

Compact Fabry–Perot Antenna With Wide 3 dB Axial Ratio Bandwidth Based on FSS and AMC Structures

The proposed antenna combines a conventional patch with an artificial magnetic conductor (AMC) ground plane and a frequency selective surface (FSS) superstrate with the height of 0.35 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (at f = 8.5 GHz) from the feed antenna. In this structure, to create circularly polarized waves, a FSS superstrate composed of an array of quasi-crescent shaped unit cells is used. In addition, to compact the antenna cavity, the AMC ground plane with the reflection phase of zero is utilized. Moreover, for further improvement in the antenna 3 dB axial ratio (AR) bandwidth (BW), an array of diagonal rectangular slots is used in the AMC ground plane. The proposed antenna presents an appropriate 3 dB AR in the whole BW (20%) of antenna with the gain up to 16 dBi. Due to high gain, wideband axial ratio, fabrication simplicity, and compact structure, this antenna is a promising candidate for X-band satellite communication, radar, wireless communication, and microwave power transmission.

Performance improvement of a slotted square patch antenna using FSS superstrate for wireless application

This paper presents a wideband planar antenna integrated with a frequency selective surface (FSS). Initially, the FSS array screen is investigated using a basic square ring to construct a unit cell of the FSS periodical structure with a (12x12) array. FR4 with a permittivity of 4.7 and a thickness of 1.6 mm is used as the substrate material for both FSS structure and antenna. Then, the antenna is placed closely parallel over the FSS configuration at a distance of 28 mm. After analyzing the performance of the antenna in terms of return loss, directivity and antenna gain, the design is integrated with the FSS structure in order to achieve a stable frequency response. Directivity and gain improvement of 6.5 dB and 5.1 dB respectively are observed along broadside direction.

Analysis and design of directive antenna using frequency selective surface superstrate

&lt;span&gt;The design of directive antenna using Frequency Selective Surface (FSS) superstrate is proposed in this project. The suitable design FSS as superstrate layer is very important to enhance the high directivity and narrow bandwidth on the antenna. By using the FSS layer to design the superstrate layer, there are able to determine the reflection coefficient accordingly to the desired frequency.&lt;/span&gt;

UWB dual‐polarised dipole array with dielectric and FSS superstrate and 65° scanning

The authors report the design of an ultra-wideband (UWB), dual-polarised, tightly coupled dipole array (TCDA) with an integrated balun for wide-angle scanning. A dual-pol dipole design enables massive bandwidth, large scanning volume, and high polarisation purity, concurrently. To achieve wide-angle impedance matching without exciting surface waves, two types of superstrates are evaluated on a finite array: (i) dielectric superstrate and (ii) novel planar frequency-selective surface (FSS). The latter architecture is capable of scanning 70° in E- plane and 65° in H- plane and shows, on average, 5° scanning improvement to the former. The impedance bandwidth is 5.25:1 (0.8-4.2 GHz) at the broadside (voltage standing wave ratio (VSWR)<;2). The bandwidth reduces to 4.3:1 (0.9-3.9 GHz) when the maximum scanning angle or θ max increases to 65° for the H -plane and 70° for the E -plane (VSWR <; 3.2). The proposed array is a great candidate for wide-angle wideband scanning applications covering the entire L and S bands.

Performance improvement of slotted elliptical patch antenna using FSS superstrate

In this article, the slotted microstrip- fed elliptical patch antenna is designed and optimized to operate at the resonance frequency of 5.38 GHz. Then, the designed patch antenna is further analyzed in a resonant cavity formed by a frequency selective surface (FSS) superstrate and antenna ground plane. The highly reflective behavior of FSS from the offset of the resonance is utilized for improving the performance of the antenna. The optimized slotted geometry produces a gain improvement of 2.5 dBi, impedance bandwidth improvement of 0.21 GHz, simultaneously at the operating resonance frequency of 5.38 GHz. After placing an FSS superstrate at a height of 28.5 mm above the antenna substrate, further improvement of 5.1 dBi gain and 0.13 GHz bandwidth is attained, For validation purpose, the prototypes of the slotted patch antenna with and without FSS superstrate are fabricated and characterized. A fairly good agreement is achieved in the measured and simulated results.

Improved Microstrip Antenna with HIS Elements and FSS Superstrate for 2.4 GHz Band Applications

This research presents a microstrip antenna integrated with the high-impedance surface (HIS) elements and the modified frequency selective surface (FSS) superstrate for 2.4 GHz band applications. The electromagnetic band gap (EBG) structure was utilized in the fabrication of both the HIS and FSS structures. An FR-4 substrate with 120 mm × 120 mm × 0.8 mm in dimension (W × L × T) and a dielectric constant of 4.3 was used in the antenna design. In the antenna development, the HIS elemental structure was mounted onto the antenna substrate around the radiation patch to suppress the surface wave, and the modified FSS superstrate was suspended 20 mm above the radiating patch to improve the directivity. Simulations were carried out to determine the optimal dimensions of the components and the antenna prototype subsequently fabricated and tested. The simulation and measured results were agreeable. The experimental results revealed that the proposed integrated antenna (i.e., the microstrip antenna with the HIS and FSS structures) outperformed the conventional microstrip antenna with regard to reflection coefficient, the radiation pattern, gain, and radiation efficiency. Specifically, the proposed antenna could achieve the measured antenna gain of 10.14 dBi at 2.45 GHz and the reflection coefficient of less than −10 dB and was operable in the 2.39–2.51 GHz frequency range.

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.

Resonant characteristics of aperture type FSS and its application in directivity improvement of microstrip antenna

In this paper, we propose an aperture type frequency selective surface (FSS) by employing an array of 12×12 unit cell elements and its resonant characteristics is analyzed. A resonant cavity antenna is then formed by the ground plane substrate and the FSS superstrate. The high reflective behavior of the proposed FSS at an offset of the resonance is then utilized for improving the performance of this cavity antenna. The impedance bandwidth and directivity are improved up to 0.66GHz and 8.95dBi, simultaneously at an optimum gap of 17.6mm between the antenna substrate and FSS superstrate. For validation purpose, prototypes of both patch antenna and FSS, are fabricated and characterized. A fairly good agreement is achieved between the measured and simulated results.

Spatially mutual coupling reduction between CP‐MIMO antennas using FSS superstrate

A new approach to suppress mutual coupling of spatial electromagnetic fields between two circularly polarised (CP) antennas using frequency selective surface (FSS) technique around 30 GHz is presented. The transmission-type FSS layer with the CP capability is placed on the top of two closely multiple-input, multiple-output (MIMO) antennas. The study shows that the FSS layer can suppress an average of 10 dB mutual coupling between two adjacent CP-MIMO antennas. The proposed technique does not degrade the impedance and radiation performance of the antenna in comparison with the antenna without FSS layer. The two-port CP antennas are fabricated and measured to validate the simulation results. Good agreement is achieved between simulated and measured results in terms of the reflection coefficient, mutual coupling, and axial ratio.

Gain Enhancement of Circularly Polarized Dielectric Resonator Antenna Based on FSS Superstrate for MMW Applications

In this communication, a high gain circularly polarized (CP) dielectric resonator antenna (DRA) is proposed. The radiating DR is coupled to a 50 Ω microstrip line through an X-shaped slot etched off the common ground plane. Using a frequency selective surface superstrate layer, a gain enhancement of 8.5 dB is achieved. A detailed theoretical analysis is given and used to optimize the superstrate size and the air gap height between the antenna and superstrate layer. The proposed DRA is designed, simulated, implemented, and tested. The high gain CP DRA has the potential to be used for millimeter wave wireless communication and imaging systems.

Erratum for: Analysis of antenna gain enhancement using new frequency selective surface superstate

In the above-mentioned article, which appeared in Microwave and Optical Technology Letters, Volume 58#2, DOI 29596, there was an error in the title. The word “SUPERSTATE” should have been “SUPERSTRATE”. The correct title is shown below: ANALYSIS OF ANTENNA GAIN ENHANCEMENT USING NEW FREQUENCY SELECTIVE SURFACE SUPERSTRATE We apologize for this error and regret any confusion that was caused.

FSS Properties of a Uniplanar EBG and Its Application in Directivity Enhancement of a Microstrip Antenna

In this letter, frequency selective surface (FSS) properties of a uniplanar electromagnetic band-gap (EBG) unit cell are studied. The unit cell consists of meander-line inductor and interdigital capacitors on one side of a substrate. Simulation results indicate that the unit cell exhibits passband characteristics centered at 10.04 GHz. FSS property of the structure is verified by measurement using X-band waveguides. The measured results show passband characteristics at 9.45 GHz. A 13 × 13 array of these unit cells (FSS screen) is used as a superstrate at a distance ≈ 0.5λ 0 over a patch antenna operating at 10.8 GHz, offset from center frequency of the FSS passband. Directivity improvement of 6.95 dB is observed along 0° in the measurements of patch antenna with FSS superstrate as compared to the patch antenna without superstrate.

60 GHz Polarization Reconfigurable DRA Antenna

This paper outlines a new polarization reconfigurable EBG (Electromagnetic Band Gap) antenna in the 60 GHz millimeter waves band. The proposed hybrid antenna is composed of a multilayer pyramidal DRA (Dielectric Resonator Antenna) exciting source covered with a FSS (frequency Selective Surface) superstrate. The device can switch between circular and linear polarization by a simple 45° mechanical rotation of the pyramidal DRA. This structure has the advantage that it maintained stable bandwidth, gain, efficiency and radiation properties when switching between the two configurations of circular and linear polarization.