Dielectric Superstrate Research Articles

A High Gain Antipodal Vivaldi Antenna Enabled by a High Dielectric Superstrate for Wideband Applications

A High Gain Antipodal Vivaldi Antenna Enabled by a High Dielectric Superstrate for Wideband Applications

High extinction ratio TE-Pass polarizer using the effect of superstrate layer in Ge-Clad optical waveguide

Attenuation characteristics of germanium (Ge) film clad planar optical waveguide are theoretically studied at the spectral wavelength of 0.6328 μm. Thin films of Ge are found to possess greater attenuation values than the other recognized materials. The existence of these greater attenuations is caused by lossy modes that are sustained by these films. It has been shown that the attenuation of the TM mode can be greatly increased by adding a high-index buffer layer between the Ge layer and the dielectric guide. It occurred because of the resonant coupling between the lossy modes supported by the Ge layer and the waveguide modes. Moreover, it is claimed that by adding a dielectric superstrate layer above the Ge thin film, the strength of the TM mode in the proposed structure can be further attenuated to an ultra-high value. In this study, a TE pass polarizer is proposed having a high extinction ratio of 30582.15 dB. Attenuation results are presented, after optimization of several parameters like thicknesses of Ge, buffer, and superstrate layers along with environmental stability of the suggested structure. The generated field distribution profiles are also in good agreement with the obtained attenuation results.

1-D Wide-Angle Scanning Phased Array With Enhanced Gain and Reduced Mutual Coupling Using Thin Dielectric Superstrate

1-D Wide-Angle Scanning Phased Array With Enhanced Gain and Reduced Mutual Coupling Using Thin Dielectric Superstrate

Design and Optimization of a Monolithic Thinned Dielectric Superstrate for Performance Enhancement in DRAA

Design and Optimization of a Monolithic Thinned Dielectric Superstrate for Performance Enhancement in DRAA

Design and Tensor Impedance Analysis of 4×4 Isotropic Homogeneous Metasurface-Backed Slotted Dual-Layered Bio-Superstrate-Loaded MPA

A 4×4 Isotropic Homogeneous Metasurface (IHM) backed, rectangular slotted dual-layered triband microstrip patch antenna (MPA) is proposed in this article. A detailed mathematical way to analyze the tensor surface impedance matrix (TSIM) of the proposed 4×4 IHM and slotted patch is demonstrated. The proposed IHM-backed MPA has a triband even-mode resonance at fr0=2.45 GHz, 2fr0=5.4 GHz, and 4fr0=7.7 GHz. A better and more accurate estimation of bio-superstrate loading effect for triband resonance is employed using the human skin (εr=52.79, σs=1.39) and blood (εr=52.8, σs=1.23) layer on the top of dual-layered metasurface-backed slotted MPA. TSIM characterization is observed for both blood- and skin layer-loaded dual-layered metasurface-backed slotted MPA. Chicken breast (εr=55.2, σs=1.49, and tanδ=0.325) with blood (εr=58.2, σs=2.59, and tanδ=0.364) is loaded onto fabricated dual-layered structure to verify numerically modeled estimation. A closed form triband, even-order resonance mode (i.e., fr0, 2fr0, and 4fr0) estimation based on dielectric superstrate thickness (Hs) is numerically established using MATLAB solver. Complete measurement setup with simulated vs. measured results is compared in this article.

Enhanced performance of microstrip antenna fabricated on a composite dielectric substrate coupled with multiple dielectric superstrates

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.

Suitability of Dual-Band, Dual-Polarized Patch Antennas with a Superstrate for the Miniaturization of Ku-Band Antenna Arrays for Automotive Applications

The extension of low-earth orbit (LEO) services to non-terrestrial mobile communications has huge potential for eliminating network white spots and providing high-speed, low-latency links with worldwide geographic coverage. State-of-the-art user terminals for mobile platforms are too large for integration into a passenger vehicle. Antenna elements loaded with a dielectric superstrate could potentially lead to a considerable miniaturization of the user terminal. As per link budget calculations, an array with a gain of 27 dBi is necessary to ensure a throughput of 25 Mbps in the downlink at the Ku-band. A conventional array with a gain of 6 dBi per element, assuming a 12 × 12 arrangement with half-wavelength spacing, would require a footprint of 36 λ2 at 10 GHz to achieve this target and appears unsuitable for automotive integration. This paper proposes a low-profile, dual-band, dual-polarized, vertically stacked patch antenna with superstrate loading and shows that the inclusion of the superstrate improves the antenna’s gain by at least 3 dB. Therefore, compared to a conventional array, a superstrate-loaded array would need only half of the number of elements to meet the target gain, thus occupying only half of the surface area, and offers better integration for automotive applications. Requiring half of the number of elements also implies considerably reduced design complexity and cost.

Wide-Angle Scanning Microstrip Patch Antenna Array for mmWave Applications with High Gain

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.

Compact and high gain slotted patch antenna with moderate bandwidth for 60 GHz applications

A compact and high gain dual semi-circular slotted patch antenna with moderate bandwidth for 60 GHz applications is presented in this article. A rectangular-shaped patch inspires this design. The slotted antenna provides an impedance bandwidth of 1.75 GHz (58.87–60.62 GHz) and a gain of 7.55 dB. The overall size of the proposed antenna is 12 × 9.5 mm2. A dielectric superstrate is used to improve the antenna bandwidth and gain. The proposed antenna with superstrate exhibits an improved bandwidth of 2.48 GHz (58.22–60.70 GHz), an enhanced gain of 11.8 dB, and an efficiency of 95%, respectively. The antenna provides stable time-domain performance (isolation, isolation phase, group delay, and fidelity factor) over the operating band. The design prototype is fabricated and tested experimentally. Measured results exhibit a good agreement with the simulated results. The proposed antenna is suitable for high data-rate radio access and high gain 60 GHz applications.

A Leay Wave Antenna With Dielectric Superstrate on Perforated Dielectric Spacer

In this paper, a leaky wave antenna with dielectric superstrate (LWADS) on the perforated dielectric spacer is proposed. The LWADS has an asymmetric structure with a half-filled dielectric spacer and with a non-filled spacer to make a quasi-cutoff region. The half-filled dielectric spacer is periodically perforated, and the beam direction of leaky wave is controlled by changing the hole radius. Generally, the unwanted radiation is occurred in the broadside direction when the beam of leaky wave is tilted with large angle, this unwanted radiation is avoided by providing these perforated dielectric spacers. The proposed design is validated by measurements at X-band, and it is shown that a high gain tilted beam pattern with peak gains of 14 dBi is obtained not only at θ = 20°, 40°, but also at the wide-angle of θ = 60°. Since the effective permittivity can be controlled by the hole radius, an array of LWADS with different beam angles can be realized with the same height, and a multi-beam antenna with switched feeding can be realized.

Phased Array With Pattern Shaping and Scan Loss Reduction for Millimeter Waves

In this work, we investigate antenna architectures to implement dual-mode operation in phased array designs. Planar slot antenna elements are used in array configuration, in combination with artificial dielectrics layers (ADLs) located in the close proximity of the array, to achieve pattern shaping. The artificial dielectric superstrate supports the propagation of leaky waves that can be optimized to enhance the gain in a specific angular region or to enlarge the array field of view. By controlling the amplitude and phase of the antenna elements, the radiation patterns can be combined to realize either wide or narrow beams. This concept present advantages for both millimeter-wave (mm-wave) communication and radar applications. A design of a four-element array fabricated in standard printed circuit board (PCB) technology validates the feasibility of the dual-mode operation. The measured results also show good agreement with simulations.

A high gain dual circularly polarized X‐band antenna for CubeSat applications

AbstractIn this article, a dual circularly polarized high gain superstrate integrated X‐band antenna is designed and analyzed for CubeSat applications. The proposed antenna consists of a metallic patch, multilayer space qualified printed circuit boards, and a dielectric superstrate with a high relative permittivity on top of the patch to establish a suitable resonance condition for high‐gain operation. The driven patch is fed by a 3‐dB hybrid coupler for the generation of dual (left hand circular polarization and right hand circular polarization) circular polarization. The antenna exhibits an impedance bandwidth of >18.5% (7.75–9.4 GHz) with a peak gain of >16 dBiC. The achieved antenna performance makes it suitable for CubeSat missions at X‐band.

Dual‐Band Huygens Source Antennas With Partially Reflective Surfaces

AbstractThis paper presents an antenna architecture from Huygens sources placed in a middle cavity formed by a metal reflector and a partially reflective surface (PRS) of dielectric superstrates. The proposed antenna is excited by a pair of cross‐feedings to produce two frequency resonances in reflection coefficients and radiate unidirectional patterns. In contrast to conventional designs, the proposed PRS‐supported Huygens source antenna may effectively broaden the bandwidth and increase radiation gains with a low profile, including low cost. Simulation results show broadband radiation characteristics at 2.45 and 5 GHz bands, where the impedance bandwidths are in the ranges of 2.4–2.5 GHz and 4.8–5.8 GHz, respectively. In addition, the measurement results of the antenna prototype validate the simulation results in terms of reflection coefficients and radiation patterns. It is found that the gains are 5.0 dBi (2.45 GHz) and 3.0 dBi (5 GHz), where simulation and measurement results are agreed well for practical applications of wireless communications.

A Study on Scattering Performance of Reflectarray Element Covered by Dielectric Superstrate

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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\theta _{i}$ </tex-math></inline-formula> on the scattering field strength is also studied. Based on inequalities that are derived from the electric field expressions, range of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\theta _{i}$ </tex-math></inline-formula> 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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\theta _{i}$ </tex-math></inline-formula> is independent of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\varepsilon _{r}$ </tex-math></inline-formula> when <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\varepsilon _{r} \gg 1$ </tex-math></inline-formula> , where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\varepsilon _{r}$ </tex-math></inline-formula> 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.

Enhanced radiation characteristics of regular dodecagon split ring resonator (D-SRR)-based microstrip patch antenna employing dielectric superstrate for THz applications

In a world where communication requires ever faster data transmission capable of transmitting high speeds. In order to reach and transmit this high speed, it is necessary to increase the frequency that carries the information. For this, scientists are interested in the terahertz (THz) range which, thanks to its high frequencies between 0.1 THz and 30 THz, offers the possibility of increasing the data rate. This letter presents the inclusion of Dodecagon Split Ring Resonator (D-SRR) in rectangular microstrip patch antenna and its effect in the performance of the proposed antenna. The metamaterial design employs two types of SRRs resonators shapes such as the Dodecagon Broadside Coupled Split Ring Resonator (DBC-SRR) and Dodecagon Split Ring Resonator (D-SRR). The model applied uses a local field approach and allowed to obtain the dispersion characteristics of discrete negative magnetic permeability. The proposed antenna substrate uses Arlon AD1000 material, which helps to attain high gain and good directivity at THz frequency. The antenna performance is investigated with and without superstrate. The operating frequencies of the proposed antenna vary in the range of 0.66 - 0.69 THz and shows maximum gain of 10.4 dB and maximum directivity of 9.84 dB. HFSS software tool helps to simulate the parametric analysis of the proposed antenna design. This novel structure may find applications in terahertz imaging, remote systems and may find manifold possibilities in the medical field.

Effect of Dielectric Cover Thickness Analysis on Rectangular Microstrip Patch Antenna in Wi-Fi Applications

This paper studies the effect of dielectric covers or superstrate with different thickness on rectangular microstrip patch antenna. The proposed antenna is designed at 2.4GHzfrequency using method of transmission line model. The dielectric covers or superstrates are providing protection to the antenna from different environmental hazards conditions. The HFSS electromagnetic simulation software is used for simulating the antenna using different dielectric superstrate covers. The different cover thickness affects is investigated on microstrip antenna and compared their performance with and without superstrates.

A Study on Gain Enhanced Leaf-Shaped Bow-Tie Slot Array Antenna within Quasi-Millimeter Wave Band

In this paper, a linear array of 4 leaf-shaped bowtie slot antennas is proposed for use in quasi-millimeter wave band. The slot antennas array is designed to operate at 28 GHz frequency band. The leaf-shaped bowtie slot antenna is a type of self-complementary antenna with low profile and low cost of fabrication. The proposed antenna structure offers improvement in radiation pattern, gain, and -10 dB impedance bandwidth. Through out of this paper radiation pattern, actual gain, and -10 dB impedance bandwidth are evaluated by Finite Different Time Domain (FDTD) simulation. Antenna characteristics are analyzed in the frequency range of 27 GHz to 29 GHz. To improve antenna characteristics such as actual gain and -10 dB impedance bandwidth, a dielectric superstrate layer with relative permittivity of 10.2 is placed on top of ground plane of the slot antennas array. Three antenna structures are introduced and compared. With two layers of dielectric superstrate on top of the antennas ground plane, analysis results show that -10 dB impedance bandwidth occupies the frequency range of 27.17 GHz to 28.39 GHz. Therefore, the operational impedance bandwidth is 1.22 GHz. Maximum actual gain of the slot antennas array with two dielectric superstrate layers is 20.49dBi and —3 dB gain bandwidth occupies the frequency range of 27.02 GHz to 28.57 GHz. To validate the analysis results, prototype of the designed slot antennas array is fabricated. Characteristics of the slot antennas array are measured and compared with the analysis results.

Dual-Layer Superstrate Structure for Decoupling of Dual-Polarized Antenna Arrays

A new antenna decoupling structure by combining metal and dielectric superstrates is studied in this letter. The decoupling concept is elaborated in a 5-element antenna array. Afterwards, the decoupling performances are validated in a 3 × 3 staggered antenna array. The dielectric superstrate serves as magnitude and phase compensators. It achieves the tradeoff design to simultaneously improve decoupling bandwidth and matching in wideband decoupling issue. The E-plane and H-plane isolations are enhanced by at least 9 dB, reaching > 23 and > 27.2 dB in the operating bandwidth of 3.4–4.2 GHz. The radiation performances are also enhanced through decoupling.

High Gain Beam Steering Antenna Arrays with Low Scan Loss for mmWave Applications

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.

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.