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The growing need for remote healthcare monitoring and personalized treatment has driven the evolution of Wireless Body Area Networks (WBAN). This paper presents a new multiband antenna design for WBAN, featuring a dual wideband antenna that operates from 2.22 to 3.52 GHz and 4.98–11.13 GHz. The design also includes an integrated 4 × 4 artificial magnetic conductor (AMC) surface and a 4 × 3 frequency selective surface (FSS) superstrate layer that works together to reduce back radiation and improve radiation performance. The AMC unit cell produces a quintuple zero-degree reflection phase response at 2.5 GHz, 4.8 GHz, 6.5 GHz, 9.1 GHz, and 11 GHz, and the FSS superstrate generates a multiband response of the transmission coefficient at 3.24 GHz, 6.68 GHz, and 9.25 GHz, behaving as a Double Negative material at their corresponding resonant frequency. The integrated antenna design measures 0.425λ0 × 0.425λ0 × 0.17λ0 (λ0 at 2.45 GHz) and covers the most common wireless frequency bands, with an impedance bandwidth of 23.74% (2.19–2.78 GHz), 1.739% (3.99–4.06 GHz), and 72.46% (5.13–10.96 GHz). Furthermore, the integrated antenna showcases a peak gain of 11.98dBi at 7.5 GHz, a notable Front-to-Back Ratio of 25.15 dB at 8.2 GHz, and a minimal specific absorption rate (SAR) of 0.0142 W/kg at 9 GHz. These accomplishments resulted in a considerable 99.45% reduction in the overall average SAR values and achieved an 83% radiation efficiency. The effectiveness of the proposed multiband antenna design was evaluated by fabricating and testing an experimental prototype using a Vector Network Analyzer and Anechoic Chamber. Overall, the integrated AMC and FSS structures enable multiband resonance and improved radiation performance, making the presented antenna design a promising solution for future WBAN applications. [ABSTRACT FROM AUTHOR]

ABSTRACT A novel superstrate‐based Vivaldi antenna design characterized by high‐gain and wideband performance is presented. The proposed design configuration features a Vivaldi antenna positioned between high dielectric superstrate (Rogers 6010, εr = 10.2) with copper etched off on both sides and an FR4 substrate that has copper etched on one side only. The introduction of a high permittivity dielectric material above and a reflector below the Vivaldi antenna enables favorable resonance conditions for achieving high‐gain operation. The measured antenna exhibits a peak gain of 17 dBi at 10 GHz, covering an operating frequency range of 6–20 GHz. It also features a narrow half‐power beamwidth and low side lobe level radiation patterns. Unlike existing studies, which rely on metamaterials, electromagnetic bandgap structures, and frequency selective surfaces for gain enhancement, our design employs high‐dielectric constant superstrates. This approach increased the antenna's peak gain by 10 dB. Also, the proposed configuration act as a radome protecting the antenna from Environment. [ABSTRACT FROM AUTHOR]

Summary: The characterization of four different materials, Taconic (D1), FR4 (D2), Lab material (D3), and Created material (D4) using the ring resonator technique, is presented in this study along with a comparison of antenna performance using standard and measured dielectric constant (εr) and loss tangent (tanδ) values. This article discussed the comparison of antenna performances on four distinct dielectric materials to verify their efficiencies. Standard values of εr for the reported materials are 2.20, 4.40, 2.33, and 10.45 for D1, D2, D3, and D4, respectively, with corresponding tanδ values of 0.0009, 0.02, 0.0012, and 0.00032. The εr and tanδ for the materials D1, D2, D3, and D4 are calculated as 2.10, 4.56, 2.51, and 9.89 and 0.00094, 0.01927, 0.0013, and 0.0003025, respectively, using a ring resonator. The materials are utilized as the substrate for a printed single layer Y‐Shape 5G‐IoT antenna in order to validate the measured results. According to the findings of this study, the measurement of εr using the resonator approach exhibited errors of 4.54%, 3.63%, 7.82%, and 5.33%, respectively, while the tanδ has errors of 04.44%, 03.65%, 08.33%, and 5.47% for materials D1, D2, D3, and D4, respectively. The outcomes of this work include the numerical calculation of the εr and tanδ of four materials and the validation of the measured values using a Y‐Shape 5G‐IoT antenna in the millimeter‐wave 5G frequency bands. Additionally, the values calculated mathematically are compared with the values obtained from the conventional ring resonator. [ABSTRACT FROM AUTHOR]

A novel, high-gain reconfigurable antenna with a metasurface (MS) superstrate-based configuration is proposed in this research article. The design utilizes a concentric octagonal-shaped patch as a base antenna. Four SMP1345-079LF PIN diode switches are incorporated in the base antenna to facilitate frequency reconfiguration. When all four of the diodes are in OFF condition, the designed antenna resonates at 5.8 GHz. Switching ON the diodes switches the resonating frequency to 5 GHz. A novel MS unit cell of shape like '8' has been designed and analyzed. The designed unit cell exhibits properties of the metamaterial in the operating frequencies. An MS superstrate of a 5 × 5 array has been designed and connected to the base antenna through Teflon rods. Further, the proposed reconfigurable antenna with MS has been analyzed for air and foam medium (medium between antenna and superstrate). The proposed structure offers better performance for the air medium with a gain enhancement of 4.23 dBi and 1.55 dBi at 5 GHz and 5.8 GHz respectively. Fabrication and testing processes are undertaken to validate the proposed antenna's performance. [ABSTRACT FROM AUTHOR]

In this study, we introduce a unique geometrical design of a rectangular patch antenna for sub-6 GHz 5G applications. The proposed antenna is designed at 5.2 GHz, and design criteria and performance characteristics have been investigated through numerical simulations and verified using measured data. A composite structure is suggested to overcome the restrictive parameters of conventional antennas. Two different materials, Rogers RT5880, and RT5870, are utilized, achieving a maximum gain of 6.210 dB, and a 90.2% radiation efficiency was attained. Four layers of superstrates are placed above the antenna to enhance the antenna's radiation performance further. The fabricated antenna is evaluated by measuring its radiation characteristics and return loss. The final antenna prototype offers a maximum bandwidth of about 896 MHz at a −10 dB reflection coefficient with a maximum gain of 9 dB. The proposed model achieved ultimate efficiency as high as 89% by employing four superstrates. The results showed good impedance matching (S11, VSWR), high efficiency, and appropriate radiation patterns. The outcomes from simulation and measurement are well aligned, making this antenna suitable for high-performance 5G applications. [ABSTRACT FROM AUTHOR]

This paper presents a modified rectangular microstrip patch antenna (MRMPA) array conforming to the hemisphere for wide-angle beam scanning. Two different conformal antenna array designs are presented in this work. The first of these designs, a 13-element MRMPA array conformal to the surface of a circular arc, and the second one, a 9-element array conformal to the surface of a hemisphere, are designed and optimized. The geometrical approach of calculating the phase value is used to calculate the phase value of each antenna. The simulated results show that the 13-element conformal MRMPA array is achieving a beam scanning angle of ±84° with a gain of 13.89 dBi with low side lobe levels, and further, the gain of the array is enhanced by a dielectric superstrate that improved the gain by ∼2 dBi at all the scanning angles. Second, an MRMPA array conformal to a hemisphere with nine elements is designed with beam scanning ability from φ = 0°−360° and θ = ±30° with a gain of 15.69 dBi, and further, the gain is enhanced by ∼3 dBi with the dielectric superstrate. Full-wave simulations have proven both designs to be accurate and aligned with theoretical calculations. [ABSTRACT FROM AUTHOR]

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Recently, electromagnetic metamaterials are of great interest to researchers because of their unusual electromagnetic properties. The proposed work presents a metamaterial as a superstrate for enhancing the performance parameters of a conventional patch antenna. The metamaterial unit cell is examined using classical waveguide theory to confirm its metamaterial properties such as permittivity and permeability at the resonant frequency. The proposed meta-structure comprises of a 5 × 5 array of circular-shaped split ring resonators backed with wire strips and placed above an inset-fed rectangular patch antenna that resonates at 9.96 GHz. The metamaterial superstrate improves the gain, impedance bandwidth, and radiation efficiency by 2.4 dBi, 770 MHz, and 18.4%, respectively and simultaneously reduces reflection coefficient by 5 dB. Several benefits such as compact size, simpler structure, low profile, and low cost have been obtained from this design. EM simulation of the proposed composite structure has been carried out with the help of the HFSS EM simulator and measurement has been done for validation. [ABSTRACT FROM AUTHOR]

In this paper, a tunable high-gain graphene-based terahertz (THz) patch antenna is implemented and numerically studied. The antenna contains a graphene patch on top of a silicon dioxide substrate with a bottom ground plane made of gold. The designed graphene antenna operates in the fundamental TM 10 mode at a resonant frequency of 0.61 THz. A single-element graphene patch antenna provides the boresight radiation pattern with a gain of 1.57 dBi, and a radiation efficiency of 32%. A double split ring resonator-shaped frequency selective surface (FSS) is designed and numerically studied to improve the gain of the graphene patch antenna. The FSS loaded at the top of the antenna formed a Fabry–Perot cavity. The antenna with superstrate improves the gain from 1.57 to 4.87 dBi and radiation efficiency from 32 to 55%. It is observed that the FSS enhanced the gain of the antenna around 3.3 dBi and improved the radiation efficiency around 23%. The three different sizes of patch antenna sub-arrays 2 × 2 , 4 × 4 , and 8 × 8 are implemented and numerically studied. The sub-arrays can be used for implementing THz massive multi-input-multi-output (MIMO) applications. The sub-array enhances the gain and it also provides flexibility in the design of the beamforming massive MIMO antenna. The multibeam can be achieved by applying different phases and amplitudes to different sub-arrays. Moreover, The designed antenna response can be tuned by applying an electrostatics DC bias, which alters the surface conductivity of the graphene patch and the tunability in the antenna response achieved. The tuning frequency range of the designed graphene patch antenna around 0.5–0.65 THz. The advantage of the THz antenna provides high-speed communication, greater bandwidth, non-ionizing signal nature and compactness. [ABSTRACT FROM AUTHOR]

This article presents a conformal monopole antenna for wearable application in ISM band frequency of 2.45 GHz. The antenna has a return loss of 50.18 dB with good radiation performance. The gain of the antenna is 1.09 dBi which is improved to 3.28 dBi using a metasurface consisting of 3 × 3 array elements. The proposed metamaterial integrated antenna is fabricated on 1 mm thick flexible PDMS substrate. The metamaterial improves the gain while reducing the specific absorption rate (SAR) of the antenna. The geometry size of the metamaterial integrated antenna is 50 × 50 × 24 mm3. The loading effect of antenna by body is analyzed with a hand phantom model. Flexibility and conformability of antenna is analyzed by bending the antenna with various radii in x and y direction. Measured results of the fabricated prototype demonstrate the safety of the suggested wearable antenna for biomedical applications. [ABSTRACT FROM AUTHOR]

This article describes the development and implementation of a circularly polarised multi-input–multi-output (MIMO) antenna that utilizes a metamaterial-based superstrate for improved gain and bandwidth for WLAN applications. The proposed antenna consists of multiple layers including ground plane, substrate, driven patch, airgap, superstrate, and metamaterial. The superstrate consisting of a novel metamaterial array structure is placed above the MIMO antenna with an air gap to enhance its performance. The proposed MIMO antenna is realized using a 1.6 mm thick FR4 for both substrate and superstrate. The driven patches are fed by a single input hybrid coupler (HC) to generate Right Hand Circular polarisation (RHCP). The overall size of the proposed antenna is 0.8 × 1.6 × 0.065 λ03, which is fabricated and tested. The measured results shows that the − 10 dB impedance bandwidth and 3 dB axial ratio bandwidth of the proposed antenna are 16% (2.3–2.7 GHz) and 5% (2.35–2.47 GHz) respectively. The antenna also demonstrates a peak gain of 7.5 dBic and isolation of < 25 dB across the operating frequency range. The radiation patterns are stable with cross polarisation level of <−15 dB. The integration of air suspended superstrate-based metamaterial improved the antenna gain by approximately 4 dBic and impedance bandwidth by 14%. Additionally, the analysis of MIMO performance metrics, demonstrates favourable characteristics suitable for MIMO applications.Kindly check and confirm that the corresponding author is correctly identified.Correct Please check and confirm the author names and initials are correct. Also, kindly confirm the details in the metadata are correct.Second authors first name spelling is incorrect, it's Imaculate not Immaculate, I have corrected it [ABSTRACT FROM AUTHOR]

Sb2S3 is rapidly developed as light absorber material for solar cells due to its excellent photoelectric properties. However, the use of the organic hole transport layer of Spiro‐OMeTAD and gold (Au) in Sb2S3 solar cells imposes serious problems in stability and cost. In this work, low‐cost molybdenum (Mo) prepared by magnetron sputtering is demonstrated to serve as a back electrode in superstrate structured Sb2S3 solar cells for the first time. And a multifunctional layer of Se is inserted between Sb2S3/Mo interface by evaporation, which plays vital roles as: i) soft loading of high‐energy Mo particles with the help of cottonlike‐Se layer; ii) formation of surficial Sb2Se3 on Sb2S3 layer, and then reducing hole transportation barrier. To further alleviate the roll‐over effect, a pre‐selenide Mo target and consequentially form a MoSe2 is skillfully sputtered, which is expected to manipulate the band alignment and render an enhanced holes extraction. Impressively, the device with an optimized Mo electrode achieves an efficiency of 5.1%, which is one of the highest values among non‐noble metal electrode based Sb2S3 solar cells. This work sheds light on the potential development of low‐cost metal electrodes for superstrate Sb2S3 devices by carefully designing the back contact interface. [ABSTRACT FROM AUTHOR]

The design and analysis of a four-port multi-input multi-output (MIMO) super wideband antenna (SWB) with a metamaterial superstrate are proposed. Initially, a single antenna is constructed with a hexagonal radiator loaded with dodecagon slots along with a slotted partial ground. An impedance bandwidth of 4.1–14.7 GHz is achieved by using symmetric coplanar waveguide feeding technique and three iterations of dodecagon slot-loaded radiating element. The design is extended to a 2 × 2 MIMO antenna with dimensions 50 × 50 × 1.6 mm3. The four symmetrical SWB antennas are placed orthogonally to each other at four corners of a square-shaped FR4 substrate. A metamaterial superstrate is used above the four-port antenna to increase the antenna's performance characteristics. A 7 × 7 array of rectangular metamaterial unit cells acts as a building block for the metamaterial superstrate to improve impedance matching, enhance isolation between the elements, and boost the antenna's gain. The metamaterial unit cells are made up of three rectangular rings that are put on top of a 1.6 mm thick FR4 substrate. With a mutual coupling of (>15 dB), the antenna achieved S11 < −10 dB for an impedance bandwidth of 11 GHz. The gain enhancement of up to 1.73 dB is obtained in C and X bands using metamaterial superstrate. The antenna characteristics mainly peak gain, return loss, bandwidth, and isolation are examined. The simulated results affirm a decent deal with experimental results. [ABSTRACT FROM AUTHOR]

This paper presents a new radar sensor configuration of a planar grid antenna array (PGAA) for automotive ultra-wideband (UWB) radar applications. For system realisation, the MIMO concept is adopted. The proposed antenna is designed to operate over the 24 GHz frequency band. It is based on split-ring resonator (SRR) elements to enhance the operating bandwidth and increase the antenna gain, leading to a better-performing radar system. The PGAA consists of thirty-one radiating elements, in which each element excitation is obtained using a common transmission line centre fed by a 50 Ω coaxial probe. By introducing a superstrate dielectric layer at a distance of λ / 2 from the top of the antenna array, the PGAA gain and impedance bandwidth are further improved. The gain is improved by 2.7 dB to reach 16.5 dBi at 24 GHz, and the impedance bandwidth is enhanced to 9.3 GHz (37.7%). The measured impedance bandwidth of the proposed antenna array ranges from 20 GHz to 29.3 GHz for a reflection coefficient ( S 11 ) of less than −10 dB. The proposed antenna is validated for automotive applications. [ABSTRACT FROM AUTHOR]

This paper investigates a nano-scaled patch antenna in optical frequency range. The proposed nanoantenna consists of a circular patch of dimension 130 × 130 nm2, placed on a glass substrate with thickness 112 nm. To protect the antenna against environmental jeopardies, a superstrate layer of dimensions 40 × 2.5 × 110.4 nm3 has been added. To enhance the performance of the antenna in terms of bandwidth and efficiency and to obtain circular polarization, multiple slots are added into the patch and ground plane of the proposed nanoantenna. The suggested antenna resonates at 182 THz with an impedance bandwidth of about 47 THz (160–207 THz) and a minimum radiation efficiency of 96.54% throughout the entire operating band. The operating bandwidth of the designed nano antenna corresponds to a wavelength range of 1449–1875 nm which covers the entire wavelength of the third optical communication window centered at 1550 nm. Besides, the proposed antenna is circularly polarized which make it very interesting in wireless communication system because it has the advantage to emit the electromagnetic radiation in a corkscrew fashion which allows efficient transmission to the receiver. The proposed antenna covers the telecom optical communication wavelength bands, S-band (1460–1530 nm), C-band (1530–1565 nm), and L-band (1565-1625 nm) in the operating range of 160 THz–207 THz. The proposed nanoantenna with circular polarization might be useful for various integrated components and variety of applications such as optical communication, nano photonics, biosensing, and spectroscopy and could play an essential role in progress of plasmonic sensors. [ABSTRACT FROM AUTHOR]

In this article, a superstrate and arrow‐shaped frequency selective surfaces (FSSs) embedded twist aperture array has been presented. In this article, a single arrow‐shaped FSS is kept in the E‐plane and the superstrate is kept above the aperture to form a circularly polarized twist waveguide array. Optimization and analysis have been carried out by commercially available software Ansys HFSS 15.0. The presented waveguide array has an input reflection coefficient ranging from 8.6 to 9.62 GHz and an axial ratio ranging from 8.7 to 9.37 GHz. Additionally, the presented array provides higher gain as compared to the conventional open‐ended WR‐90 twist waveguide. [ABSTRACT FROM AUTHOR]

In this paper, a high refractive index-based metamaterial Bi-convex lens superstrate for the gain enhancement of broadside radiating antennas like microstrip antennas is presented. Fundamentally, an effective HRI medium is created by the Single Ring Split Ring Resonator unit cells printed on an FR-4. By stacking the multiple layers of the superstrate, a virtual HRI-based equivalent Bi-convex lens is constructed to focus the incoming diverged beam from a patch antenna. A gain enhancement of 4.42 dB is achieved with the help of a 3-layer HRI-based Lens superstrate. The simulation and measurement results are also almost agreed on the same. [ABSTRACT FROM AUTHOR]

In this article, a novel double-face logarithmic spiral metamaterial (LSMTM) superstrate-inspired multiple-input multiple-output (MIMO) for fully enhanced circularly polarized (CP) antenna system is examined for 5G wireless communications. This novel double-face LSMTM superstrate acts as a planar concave-concave lens. Initially, the antenna is designed with a circular spiral patch to generate CP radiation in the frequency band of interest. Then, at a height of 6.5 mm (0.606 λo) above the MIMO antenna, which has a 0.8 mm (0.075 λo) edge-to-edge separation, the LSMTM superstrate is employed for isolation, gain, and bandwidth improvement. The proposed superstrate enhances the isolation, gain, and bandwidth of the antenna by about 32 dB, 3.47 dB, and 900 MHz, respectively. In contrast to the conventional technique of verifying operation with a simulated surface current distribution, characteristic mode analysis (CMA) is used to provide a better explanation of the proposed antenna's different modes and the creation of circular polarization. Additionally, the CMA supports the development of an effective technique that can predict whether or not the isolation can be further improved. The simulated results align with the measured results and are well adapted for 5G wireless communication devices. [ABSTRACT FROM AUTHOR]

In this article, frequency selective surfaces (FSS) and superstrate embedded waveguide aperture arrays have been proposed. Three FSS are embedded in the transverse‐plane in WR‐90 waveguide and the unit superstrate cell is kept at a certain distance to achieve circular polarization. Optimization and analysis have been done by commercially available software Ansys HFSS 16.0. The proposed array has dual‐band behavior with input reflection coefficient ranges from 8.5 to 9.53 GHz and 10.15 to 10.49 GHz. Further analysis shows that the presented array has a higher gain as compared with the conventional open‐ended WR‐90 waveguide. In addition, the proposed array also provides low cross‐polarization and 5–6 dBi higher gain compared with the open WR‐90 waveguide array. [ABSTRACT FROM AUTHOR]

In this article, effect of a dielectric superstrate on scattering performance of reflectarray elements is clarified. At first, analytical electric field expressions of an infinite line current backed by a ground plane with the dielectric superstrate and so-called resonance conditions derived by Sugio et al., are reviewed. According to the electric field expressions and reciprocity, enhancement of the scattering field strength by the dielectric superstrate under the resonance conditions is expressed analytically. Since the scatterers are illuminated by the incident wave arriving from outside of the scatterers, the effect of its incident angle $\theta _{i}$ on the scattering field strength is also studied. Based on inequalities that are derived from the electric field expressions, range of $\theta _{i}$ for enhancing the scattering field strength by the dielectric superstrate under the resonance conditions is found. As a result, it is found that the range of $\theta _{i}$ is independent of $\varepsilon _{r}$ when $\varepsilon _{r} \gg 1$ , where $\varepsilon _{r}$ is relative permittivity of the dielectric superstrate. Numerical simulation is performed, and it is demonstrated that the analytical formulae derived here are useful for predicting the effect of the dielectric superstrate on practical reflect array elements such as dipole, patch, and loop elements. Results and theories demonstrated in this article give quantitative guidelines on designing the reflectarray elements covered by the superstrate from the viewpoints of angle dependence, geometry, and permittivity of the superstrate. [ABSTRACT FROM AUTHOR]

In this communication, a new method of embedding an annular ring into the superstrate is proposed and studied to reduce the negative effect of the superstrate on the microstrip omnidirectional antenna. The working mechanism of the annular ring is analyzed based on the E-field distributions and an equivalent model that can approximately determine the dimensions of the annular ring. The effect of the parameters of the superstrate and the annular ring on the antenna performance is analyzed to verify the equivalent model. With the help of the annular ring, the negative effect of deep ripples in the radiation pattern, the strong radiation at the lower hemisphere, and the sensitiveness of the radiation pattern to the ground size from the superstrate are mitigated. A fabricated prototype shows that the measured −10 dB impedance bandwidth is 0.7 GHz (12.9–13.6 GHz). Within the frequency range of 13–13.8 GHz, the measured radiation patterns have no deep ripples and the measured radiation at the lower hemisphere is weak. The proposed method of embedding an annular ring to the superstrate, which does not involve the optimization of superstrate’s parameters, can serve as a promising candidate in practical applications. [ABSTRACT FROM AUTHOR]

In this work, a compact inset-fed microstrip patch antenna integrated with a double negative metamaterial superstrate is presented for terahertz applications. A rectangular-shaped inset-fed antenna is utilized as the main radiator, which gives an impedance bandwidth of 1.281–1.354 THz. To improve the bandwidth and gain characteristics, a nested rectangular ring-shaped metamaterial structure is designed. This structure shows double negative properties at the resonance frequency, which enhances the gain and bandwidth simultaneously. The designed antenna achieves a gain improvement of 1.9 dB at Φ = 0° and Φ = 90°. A reflection coefficient of −24 dB is achieved with a bandwidth enhancement of 26% at 1.32 THz. The antenna maintains very good radiation characteristics, and the peak gain value reaches 7.72 dB at 1.32 THz. This metamaterial-based antenna can be used for biomedical, imaging, and radar applications. [ABSTRACT FROM AUTHOR]

To design a low radar cross section (RCS) antenna, the major concern is not only to reduce scattering, but also to maintain its radiation parameters, viz. gain, voltage standing wave ratio (VSWR), etc. This paper presents a simple configuration of low RCS microstrip patch array with a periodic structure-based superstrate. The ground of the array is designed as reduced ground plane with high impedance surface elements, viz. rectangular patch and Jerusalem cross. The configuration of superstrate consists of multilayered, viz., two-layered and three-layered structures having partially absorbing and reflecting surfaces. In both the proposed configurations, the array gain of 12.5 dB is maintained with reduced structural RCS over the entire in-band frequency range. The reflection coefficient (~ −20 dB) and VSWR (~ 1.1) of the array are maintained. It is shown that the proposed superstrate-based patch array design has significantly reduced in-band RCS (−18 dBsm) at its resonant frequency. [ABSTRACT FROM AUTHOR]

This article presents the design and analysis of a high‐gain rectangular slot antenna with an operating band (intersection between the −10 dB impedance band and the 3 dB gain band) of 6–10 GHz with peak gain of ~12 dBi. To achieve this, an offset fed slot antenna is loaded with two pairs of conducting sheets—a reflector‐superstrate pair, and a pair of side sheets. The offset feeding of the slot provides wideband bidirectional radiation; subsequent reflector‐superstrate loading enables directional beam with higher gain and wider impedance bandwidth, and finally, the side sheet loading equalizes the gain over frequency band, resulting in a wider operating 3 dB gain‐band. The optimized antenna has size 2.28 λ0 × 1.34 λ0 × 0.46 λ0 at the mid‐band frequency which in measurement provides a 3 dB gain‐band of 6.03–9.77 GHz (47.34%) with 12.04 dBi peak gain, verifying the simulation. This wide gain‐band antenna is superior to existing wideband‐high‐gain antennas as it provides high‐peak gain and wide gain‐band, which is more than 90% of the impedance band. [ABSTRACT FROM AUTHOR]

Resonate cavity antennas (RCAs) with metallic superstrate, whose slot structure leads to an intense inductive property, resulting in high reflection coefficients, typically have a narrow bandwidth. This study explores designing wideband RCAs using a double‐layer metallic superstrate. Two metallic layers with an air gap that can be considered a cascade capacitance, are expected to significantly reduce the metallic superstrate's inductive property and thereby the reflection coefficient. As a sample, an RCA using a double‐layer metallic superstrate working at 10 GHz and with a size of 3 λ0 × 3 λ0, where λ0 is the wavelength corresponding to the working frequency, is designed, fabricated and measured. Results show that the proposed RCA achieves a wide bandwidth up to 18.25% (from 9.51 to 11.42 GHz) and gets a gain of 17.31 dBi at the working frequency of 10 GHz. [ABSTRACT FROM AUTHOR]

This work explains an efficient combination of the artificial magnetic conductor (AMC) based metasurface (MS) and metamaterial (MTM) based superstrate inserting between the two sides of a radiating monopole antenna applicable for C-band airborne application. The antenna is based on low volume and multilayer configuration on which a compact AMC-MS reflector is placed below the radiator antenna and reflective type MTM superstrate placed above the radiating antenna forming a resonant cavity for obtaining enhanced impedance bandwidth (IBW), miniaturized antenna dimensions with lower antenna volume compared with existing multilayer antenna designs. The final MTM superstrate-loaded antenna provides a total size of 32 mm × 32 mm × 16.8 mm. Due to MTM superstrate loading, the final antenna provides an extended IBW of 15.64%, an improved gain of 7.26 dBi, and higher gain-to-area ratio of 16.42 by maintaining the compactness. Moreover, the final antenna provides positive gain values better than 2.18 dBi for theta = ± 45° and phi = 0°–360° for the complete working band. Hence, the proposed cavity resonator antenna can be easily fitted inside the airborne devices and provide an excellent broadside radiation performance. [ABSTRACT FROM AUTHOR]

In millimeter-wave (mmWave) communications, the antenna gain is a crucial parameter to overcome path loss and atmospheric attenuation. This work presents the design of two cylindrical conformal antenna arrays, made of modified rectangular microstrip patch antenna as a radiating element, working at 28 GHz for mmWave applications providing high gain and beam steering capability. The microstrip patch antenna element uses Rogers RO4232 substrate with a thickness of 0.5 mm and surface area of 5.8 mm × 5.8 mm. The individual antenna element provides a gain of 6.9 dBi with return loss bandwidth of 5.12 GHz. The first antenna array, made by using five conformal antenna elements, achieves a uniform gain of approximately 12 dBi with minimal scan loss for extensive scan angles. In the second antenna array, a dielectric superstrate using Rogers TMM (10i) was used to modify the first antenna array. It enhanced the gain to approximately 16 dBi while still maintaining low scan loss for wide angles. The proposed array design method is very robust and can be applied to any conformal surface. The mathematical equations are also provided to derive the array design, and both array designs are verified by using full-wave simulations. [ABSTRACT FROM AUTHOR]

A superstrate loaded cylindrical dielectric resonator antenna is developed and demonstrated for dual-band circular polarization. The proposed antenna employs a microstrip-fed rotated cross-shaped slot coupling technique for exciting the dielectric resonator (DR). The design is developed in a straight forward way. Firstly, the DR is coupled with a conventional plus-shaped slot and operates in linear polarization mode at 7.4 and 11.2 GHz. Secondly, the slot is rotated by 10° to enable out-of-phase excitation and ensure circular polarization at the above-mentioned frequencies. In the third step, a square dielectric superstrate is placed above the DR which creates multiple reflection and enhance the gain up to ~8 dBi in both the frequencies without affecting other performances. The development stages are discussed in detail. The proposed design is demonstrated through prototype fabrication and characterization. This antenna can be used for X-band satellite communications. [ABSTRACT FROM AUTHOR]

Recently, a lot of research has been carried out on different techniques to improve the performance of microstrip patch antenna (MPA). Here, we have overviewed and summarized various techniques which has been invented in past to improve the gain and of the MPA. The addition of frequency selective surface (FSS), metallic reflectors, metamaterial, parasitic patches, air gap, superstrate, shorting pins, defective ground structure and partial substrate removal are some known techniques to improve antenna gain. This paper helps to decide the best technique of gain improvement for MPA. [ABSTRACT FROM AUTHOR]

This paper reports a model to determine effective permittivity (εeff) and resonant frequency (fr) of microstrip patch antenna (MPA) covered with multiple dielectric layers. This model is augmented with a newly developed empirical expression to determine the εeff of multi-layered superstrates over a substrate. The development of empirical formulation makes use of conformal mapping approach (CMA) and series-parallel combination of dielectric boundaries between the ground plane and patch of the MPA. In this work, the MPA is designed on substrate having dielectric constant of ε1 whereas the superstrate layers have dielectric constants of ε2, ε3 ...εn. It is shown that the proposed technique is able to predict the fr of MPA with error of 1.8%, 3.5%, and 1.4% when it is covered with a single dielectric layer with superstrate height of 4.5mm for respective conditions of ε1 = ε2, ε1 > ε2 and ε1 2 (ε1 = 3.66, ε2 = 2.2/4.7). Furthermore, the developed technique is analyzed for distinct combination of substrate and two superstrate layers for the cases ε1 = ε2 > ε3, ε1 = ε2 3, ε1 2 > ε3, ε1 > ε2 3, and ε1 > ε2 > ε3. Subsequently, the viability of the proposed technique is demonstrated in practical scenarios for body centric communications by considering single (e.g., jeans cotton, pure cotton, rayon, polyester, felt fabric, terry wool, and leather) and multiple (e.g., wool over jeans cotton and polyester, felt fabric over pure cotton and rayon) layers of textiles over MPA. The measurement results on various dielectric superstrates and textiles show excellent agreement with the corresponding theoretical results and thereby validate the reported theory. Finally, a comparison with the seminal works clearly shows the promise of the reported technique in this paper.

In this paper, a ε-negative metasurface superstrate is proposed for mutual coupling reduction of large antenna arrays. Unlike the previous decoupling metasurface works that are mostly confined to two-ports antennas, the proposed decoupling superstrate can be extended to massive multiple-input multiple-output (MIMO) systems. A 4 × 4 antenna array is used as an example to illustrate the decoupling performance of the proposed metasurface. With the decoupling metasurface, the worst mutual coupling of the antenna array is improved by 8 dB over the operation bandwidth with a maximum mutual coupling reduction of 25 dB. Moreover, the decoupling metasurface also help restore the radiation patterns, bring down the active voltage sanding wave ratio, and broaden the bandwidth of the array.

• A Temperature of at least 530 °C is required for a high crystalline kesterite absorber. • CdS buffer layer is completely alloyed at 550 °C. • Crystallinity has a critical effect on the defect density and photovoltaic performance. Kesterite based on Cu 2 ZnSnS 4 composition is considered as a promising absorber material for the next generation of photovoltaics due to raw materials abundance and low toxicity. Developing a superstrate architecture using kesterite as an absorber could be the key to a better performance, which allows new ways of engineering the formation of a kesterite thin film. In this work, we study the effects of the sulfurization temperature on the crystallization of kesterite film when is fabricated in a superstrate architecture, and how this affects the performance of a solar cell. We noted that the temperature affects the final composition of the absorber due to cadmium diffusion at 500 °C from the CdS layer, while the temperature above 530 °C is essential for a complete Zn incorporation into the crystal structure. The crystallinity is highly affected, and a temperature of 550 °C is found to be favorable for the crystal growth, and the fabricated device gave improved performance. Impedance spectroscopy measurements suggest the performance enhancement is due to the reduction of defects and an increase of the depletion width in the p-n junction. [ABSTRACT FROM AUTHOR]

In this paper, a fractal inspired metamaterial superstrate is proposed for the gain enhancement of microstrip patch antenna resonating at 2.4 GHz. Fractal structure is used as the metamaterial unit cell, which is designed on a FR4 substrate with a thickness of 1.6 mm. The metamaterial unit cell exhibits near-zero refractive index at 2.4 GHz. The superstrate consists of a 2×2 array of metamaterial unit cells which acts as a partial reflective surface of Fabry-Perot (FP) cavity. The distance between the antenna and the superstrate is optimized by the FP resonance condition. The antenna has a directional radiation pattern more than the microstrip patch antenna. The antenna gives a peak gain of 7 dBi with a gain enhancement of 4 dB and a beamwidth reduction of 23° and 2° along H plane and E plane respectively. The aperture efficiency of the antenna is 80.47%. The whole structure is simulated and analyzed using finite element method. The simulated and the measured results show good agreement. [ABSTRACT FROM AUTHOR]

Using metamaterials on the top of the antenna’s accordance to magneto-dielectric superstrate and near zero refraction index theories causes improvement of radiation efficiency and gain of antennas. In this article, two novel metamaterial unit cells are proposed for gain and bandwidth improvement of Cylindrical Dielectric Resonator Antenna (CDRA). The first metamaterial unit cell is a negative magnetic structure including two rings implemented on both sides of RT/doroid 5880 substrate with dielectric constant of 2.2. Besides, the second metamaterial unit cell is a Double Negative Structure (DNG) realized consisting of two rings printed in one side and a thin wire in other side of RT/doroid 5880 substrate. Two 7 7 arrays of proposed unit cells are considered and used as superstrate layers on the top of a CDRA. Also, the CDRA is made of RT/doroid 6010 material with dielectric constant of 10.2 working at the frequency of 10 GHz. Using proposed metamaterial structures as superstrate layers on the top of the CDRA causes gain and bandwidth improvement up to 3.3 dB and 4.8%, respectively. CDRA in the presence of proposed metamaterial superstrates are analyzed using a 3D full-wave simulator. [ABSTRACT FROM AUTHOR]