Gain Enhancement Of Antenna Research Articles

Wideband slot antenna gain enhancement using metasurface reflector

Wideband slot antenna gain enhancement using concentric square and circular loop metasurface reflector (SCLMR) is presented in this paper. In two steps, the design is realized. The analysis design of a FSS-based SCLMR unit cell is included in the first step. The SCLMR structure is made up of resonant metallic square-loop and inner circular loop structures. In terms of bandwidth, the unit cell structure can be considered as a stop-band filter (2.5 GHz-6.5 GHz). The design of a wideband slot antenna (29 mm × 24 mm × 1.57 mm) is included in the second step. EM simulation tool is used to analyze, design, optimize, and validate the proposed unit cell and slot antenna combination. CST microwave studio is utilized to design and analyze a slot antenna and a unit cell in this study. The computed result of an antenna with SCLMR indicates a 101.21 % operational impedance bandwidth (2.76 GHz to 8.41 GHz). With SCLMR, the antenna has a high gain of 8.75 dBi. The designed antenna structure provides a gain enhancement of 5.50 dBi while in comparison to the same antenna without SCLMR.

Angularly stable frequency selective surface for the gain enhancement of isolated multiple input multiple output antenna

AbstractA metasurface is highly useful for improving the performance of patch antennas and reducing their size due to their inherent and unique electromagnetic properties. In this research work, we design a wideband bandstop reflector‐based frequency selective surface (FSS). It consists of a periodic array of circular shape metallic rings with four stubs. The FSS unit cell resonates over a frequency band from 7.2 to 9.2 GHz and has excellent stability under different polarizations and incident angles. A microstrip patch‐based isolated multiple input multiple output (MIMO) antenna is designed that operates over a frequency band of 7.9GHz to 8.7 GHz. The MIMO antenna and FSS are printed on the one face of a substrate. The radiation performance such as gain and directivity of the antenna is improved due to parasitic radiation of the surface and coherent‐ superposition of energy in the far‐field, between the antenna and FSS unit cells. Where the other parameters such are efficiency, radiation pattern and isolation are well preserved. The designed structure shows low complexity during fabrication. The simulated and experimental results confirm the predicted antenna performance and gain enhancement.

A dielectric free near field phase transforming structure for wideband gain enhancement of antennas

The gain of some aperture antennas can be significantly increased by making the antenna near-field phase distribution more uniform, using a phase-transformation structure. A novel dielectric-free phase transforming structure (DF-PTS) is presented in this paper for this purpose, and its ability to correct the aperture phase distribution of a resonant cavity antenna (RCA) over a much wider bandwidth is demonstrated. As opposed to printed multilayered metasurfaces, all the cells in crucial locations of the DF-PTS have a phase response that tracks the phase error of the RCA over a large bandwidth, and in addition have wideband transmission characteristics, resulting in a wideband antenna system. The new DF-PTS, made of three thin metal sheets each containing modified-eight-arm-asterisk-shaped slots, is significantly stronger than the previous DF-PTS, which requires thin and long metal interconnects between metal patches. The third advantage of the new DF-PTS is, all phase transformation cells in it are highly transparent, each with a transmission magnitude greater than − 1 dB at the design frequency, ensuring excellent phase correction with minimal effect on aperture amplitude distribution. With the DF-PTS, RCA gain increases to 20.1 dBi, which is significantly greater than its 10.7 dBi gain without the DF-PTS. The measured 10-dB return loss bandwidth and the 3-dB gain bandwidth of the RCA with DF-PTS are 46% and 12%, respectively.

Radar cross section reduction and gain enhancement of slot antenna using polarization conversion metasurface for X‐band applications

A compact metasurface loaded slot antenna with wide impedance and radar cross section (RCS) bandwidths and a high gain is reported in this communication. The proposed polarization conversion metasurface (PCMS) and its mirror image is arranged into four quadrants and placed atop the slot antenna. A 10-dB monostatic RCS reduction from 7.85 to 12.25 GHz is achieved due to the 180° phase difference of the reflected waves from the PCMS and its mirror image. The gain of the proposed structure gets enhanced by almost 3 dB compared to the radiator alone, throughout the operating band, by partially removing the PCMS just above the slot radiator. The antenna is suitable for use in stealth applications in X-band communication. The antenna structure is fabricated and measured and a good agreement is observed between the simulated and measured results.

Metamaterial array based meander line planar antenna for cube satellite communication

This research article presents a design and performance analysis of a metamaterial inspired ultra-high frequency (UHF) compact planar patch antenna for the CubeSat communication system that could be smoothly integrated with commercially available 2U Cube Satellite structure and onboard subsystem. The proposed antenna consists of two layers, one is two different width meander line antenna patch with partial ground plane and another layer is 3 × 2 near-zero-indexed metamaterial (NZIM) metamaterial array structure with ground plane. The NZIM array layer has been utilized to minimize the coupling effect with Cube Satellite structure and improve the frequency stability with enhanced antenna gain and efficiency. The fabricated antenna can operate within the lower UHF frequency band of 443.5–455 MHz. with an average peak gain of 2.5 dB. The designed antenna impedance stability characteristic has been explored after integration with the 2U Cube Satellite body layout. Besides, the antenna communication performance has been verified using 2U Cube Satellite free space path loss investigation. Small antenna volume with trade-off between the antenna size and performance are the key advantages of the proposed design, as the antenna occupies only 80 × 40 × 3.35 mm3 space of the 2U Cube Satellite body structure and the geometrical parameters can be designed to provide the best performance between 449 and 468.5 MHz.

Compact PIFA Antenna with High Gain and Low SAR Using AMC for WLAN/C-band/5G Applications

In this paper, a novel low profile planar inverted-F antenna (PIFA) with high gain and low specific absorption rate (SAR) using a miniaturized artificial magnetic conductor (AMC) is investigated. The performance of the PIFA antenna is analyzed with AMC to understand the contribution of AMC. The gain enhancement of the PIFA antenna is achieved by applying AMC below the antenna. Furthermore, the placement of AMC also reduces the SAR of the antenna and improves the antenna front-to-back ratio (FBR). The proposed antenna when measured has an impedance bandwidth of 4.8–6.7 GHz (33% with center frequency at 5.75 GHz) which is suitable for Wireless Local Area Network (WLAN), satellite uplink C-band, and sub-6 5G applications with the maximum gain of 7.6 dBi. The performance of the proposed antenna is analyzed by full-wave commercial electromagnetic software and verified by measurements.

Inductively tuned modified split ring resonator based quad band epsilon negative (ENG) with near zero index (NZI) metamaterial for multiband antenna performance enhancement

An inductively tuned modified split-ring resonator-based metamaterial (MTM) is presented in this article that provides multiple resonances covering S, C, X, and Ku-bands. The MTM is designed on an FR-4 substrate with a thickness of 1.5 mm and an electrical dimension of 0.063λ × 0.063λ where wavelength, λ is calculated at 2.38 GHz. The resonator part is a combination of three squared copper rings and one circular ring in which all the square rings are modified shaped, and the inner two rings are interconnected. The resonance frequency is tuned by adding inductive metal strips in parallel two vertical splits of the outer ring that causes a significant shift of resonances towards the lower frequencies and a highly effective medium ratio (EMR) of 15.75. Numerical simulation software CST microwave studio is used for the simulation and performance analysis of the proposed unit cell. The MTM unit cell exhibits six resonances of transmission coefficient (S21) at 2.38, 4.24, 5.98, 9.55, 12.1, and 14.34 GHz covering S, C, X, and Ku-bands with epsilon negative (ENG), near-zero permeability, and near-zero refractive index (NZI). The simulated result is validated by experiment with good agreement between them. The performance of the array of the unit cells is also investigated in both simulation and measurement. The equivalent circuit modeling has been accomplished using Advanced Design Software (ADS) that shows a similar S21 response compared to CST simulation. Noteworthy to mention that with the copper backplane, the same unit cell provides multiband absorption properties with four major absorption peaks of 99.6%, 95.7%, 99.9%, 92.7% with quality factors(Q-factor) of 28.4, 34.4, 23, and 32 at 3.98, 5.5, 11.73 and 13.47 GHz, respectively which can be applied for sensing and detecting purposes. The application of an array of the unit cells is investigated using it as a superstrate of an antenna that provides a 73% (average) increase of antenna gain. Due to its simple design, compact dimension with high EMR, ENG property with near-zero permeability, this multiband NZI metamaterial can be used for microwave applications, especially for multiband antenna gain enhancement.

Bandwidth and gain enhancement of composite right left handed metamaterial transmission line planar antenna employing a non foster impedance matching circuit board

The paper demonstrates an effective technique to significantly enhance the bandwidth and radiation gain of an otherwise narrowband composite right/left-handed transmission-line (CRLH-TL) antenna using a non-Foster impedance matching circuit (NF-IMC) without affecting the antenna’s stability. This is achieved by using the negative reactance of the NF-IMC to counteract the input capacitance of the antenna. Series capacitance of the CRLH-TL unit-cell is created by etching a dielectric spiral slot inside a rectangular microstrip patch that is grounded through a spiraled microstrip inductance. The overall size of the antenna, including the NF-IMC at its lowest operating frequency is 0.335λ0 × 0.137λ0 × 0.003λ0, where λ0 is the free-space wavelength at 1.4 GHz. The performance of the antenna was verified through actual measurements. The stable bandwidth of the antenna for |S11|≤ − 18 dB is greater than 1 GHz (1.4–2.45 GHz), which is significantly wider than the CRLH-TL antenna without the proposed impedance matching circuit. In addition, with the proposed technique the measured radiation gain and efficiency of the antenna are increased on average by 3.2 dBi and 31.5% over the operating frequency band.

Gain Enhancement of a Traditional Horn Antenna using 3D Printed Square-Shaped Multi-layer Dielectric Lens for X-band Applications

In this work, gain of a traditional horn antenna is enhanced up to 2.9 dB over X-band using 3D printed square-shaped multi-layer lens. For this purpose, firstly the multi-layer lenses are designed using Invasive Weed Optimization (IWO) and simulated in 3-D CST Microwave Studio (MWS) environment as consisting of square-shaped five layers with variable dielectric constants and heights. Thus, optimum values of the dielectric constants and heights are resulted limiting from 1.15 to 2.1 and 9.2 mm to 10 mm, respectively compatible for Fused Deposition Modeling (FDM) based 3D-printing process. Finally, the optimum lens is realized by 3D printer via FDM evaluating infill rate of cheap Polylactic Acid (PLA) material for each layer. The simulated and measured performance of the multi-layer dielectric structures are hand to hand. The horn antenna equipped by our proposed dielectric lens achieves gain enhancement of the traditional antenna up to 2.9 dB over the operation band. Furthermore, the proposed design is compared with the counterpart designs in literature and based on the comparison results it can be said that the proposed design achieves the better performance in the smaller in size as equipped a traditional X-band horn antenna.

Circularly polarized sequentially rotated antenna array for dual‐band WLAN applications

This article presents a dual-band circularly polarized (CP) 2 × 2 sequentially rotated (SR) antenna array with four slot antennas, a wideband sequential-phase shifter (SPS), and reflected plane for wireless local area network (WLAN) operations. By designing the four slot antennas for dual-band CP operations, the wideband SPS including four outputs with a sequential phase shift of 90° for improving bandwidth, and a conductor-backed reflected plane for enhancing antenna gain, a high-gain and dual-band CP SR antenna array can be realized. The measured impedance bandwidth for return loss of 10 dB is 93.81% (2.36-6.5 GHz). Both measured CP bandwidths for axial ratio of 3 dB are 22.64% (2.35-2.95 GHz) and 49.16% (4.5-6.77 GHz), which can cover all the WLAN bands. Maximum antenna gains are 12.32, 9.91, and 11.66 dBic in the range of 2.4 to 2.484, 5.15 to 5.35, and 5.725 to 5.875 GHz, respectively.

Wide-band gain enhancement of a pyramidal horn antenna with a 3D-printed epsilon-positive and epsilon-near-zero metamaterial lens—CORRIGENDUM

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A novel miniaturized dual-layer frequency selective surface

A novel dual-layer frequency selective surface (FSS) with extended cross-dipole structure is reported in this paper. The elementary form of the FSS is designed at high frequency which is then made to operate at low frequency by increasing the arm length without increasing the footprint of the FSS. The extended arm runs on both the sides of the printed circuit board (PCB) where the connection is accomplished using plated through-hole (PTH) vias. The miniaturized FSS unit cell provides band-stop response at 1.6 GHz within a small footprint of 0.026λo × 0.026λo (5 mm × 5 mm) where λo is the free-space wavelength. The proposed unit cell has rotational symmetry and hence provides good polarization stability. The angular stability is investigated and stable shielding effectiveness performance is witnessed. The proposed FSS offers angular stability up to 60 degrees. The prototype FSS screen is fabricated and the measurement results are presented. The measured shielding effectiveness is greater than 26 dB for both TE and TM mode of operation. The proposed FSS is suitable for antenna gain enhancement and radome applications in L-band.

Radiation Efficiency Enhancement of Graphene Plasmonic Devices Using Matching Circuits

In the present work, the radiation properties of a graphene plasmonic patch antenna are investigated and enhanced in terms of efficiency, utilizing circuit-matching techniques. Initially, the reflection coefficient of graphene surface waves due to discontinuities is studied, while the power flow towards free-space is numerically extracted. This analysis indicates that the radiated power is increased for higher values of the chemical potential, although the surface wave is weakly confined and prone to degradation due to interference. For this reason, a graphene sheet that supports strongly confined surface waves is terminated via a matching layer, in order to enhance the radiating power. In particular, the matching layer consists of an appropriately selected larger chemical potential value, in order to minimize the reflection coefficient and boost the radiation performance. The numerical investigation of this setup validates the upgraded performance, since the radiating power is significantly increased. Then, a realistic setup that includes a graphene patch antenna is examined numerically, proving the augmentation of the radiation efficiency when the matching layer is utilized. Finally, the latter is designed with a graded increment in the chemical potential, and the computational analysis highlights the significant enhancement of the graphene plasmonic antenna gain towards the desired direction. Consequently, a more reliable framework for wireless communications between plasmonic devices at THz frequencies is established, which corresponds to the practical significance of the proposed methodology for improved radiation efficiency. All numerical results are extracted by means of an efficient modification of the Finite-Difference Time-Domain (FDTD) scheme, which models graphene accurately.

Gain enhancement of a CPW-fed dipole antenna using a novel multiband planar artificial magnetic conductor surface for UWB applications

Gain enhancement of a CPW-fed dipole antenna using a novel multiband planar artificial magnetic conductor surface for UWB applications

Gain enhancement of a CPW-fed dipole antenna using a novel multiband planar artificial magnetic conductor surface for UWB applications

Gain enhancement of a CPW-fed dipole antenna using a novel multiband planar artificial magnetic conductor surface for UWB applications

Dual-Polarized Antenna Gain Enhancement Using Dielectric Slab Superstrate and its Application in Forming an Array

The use of dielectric slab superstrate (DSS) is proposed for gain enhancement of dual-polarized patch antenna and the corresponding arrays. The DSS for a single antenna is investigated firstly to lay a solid foundation for the design of DSS for large arrays. The DSS is placed in front of the dual-polarized aperture-coupled patch antenna and is proved to be available for gain enhancement for both polarizations. The measured results show that the DSS has little effect on the impedance bandwidth but can increase the gain by 10.7 and 11.2 dB for the two ports, respectively. Different from the existing research work, the DSS used to enhance the gain for large arrays is discussed. A piecewise homogeneous DSS with slots is proposed and fabricated for 2 ×2 array with a measured peak gain of 18.3 and 18.4 dBi for two polarizations. The piecewise homogeneous DSS and source antenna array hold the advantages of high gain, large aperture efficiency and easy processability. The piecewise homogeneous DSSs for 4×4 and 8×8 array are also designed and the simulated results show that the DSS can be effective for larger arrays.

Metamaterial-Inspired Antennas: A Review of the State of the Art and Future Design Challenges

Metamaterials are artificial structures with the ability of exhibiting unusual and exotic electromagnetic properties such as the realisation of negative permittivity and permeability. Due to their unique characteristics, metamaterials have drawn broad interest and are considered to be a promising solution for improving the performance and overcoming the limitations of microwave components and especially antennas. This paper presents a detailed review of the most recent advancements associated with the design of metamaterial-based antennas. A brief introduction to the theory of metamaterials is provided in order to gain an insight into their working principle. Furthermore, the current state-of-the-art regarding antenna miniaturisation, gain and isolation enhancement with metamaterials is investigated. Emphasis is primarily placed on practical metamaterial antenna applications that outperform conventional methods and are anticipated to play an active role in future wireless communications. The paper also presents and discusses various design challenges that demand further research and development efforts.

Wide-band gain enhancement of a pyramidal horn antenna with a 3D-printed epsilon-positive and epsilon-near-zero metamaterial lens

AbstractIn this article, we present a simple, low-cost solution for the gain enhancement of a conventional pyramidal horn antenna using additive manufacturing. A flat, metamaterial lens consisting of three-layer metallic grid wire is implemented at the aperture of the horn. The lens is separated into two regions; namely epsilon-positive and epsilon-near-zero (ENZ) regions. The structure of the ENZ region is constructed accounting the variation of relative permittivity in the metamaterial. By the phase compensation property imparted by the metamaterial lens, more focused beams are obtained. The simulated and measured results clearly demonstrate that the metamaterial lens enhances the gain over an ultra-wide frequency band (10–18 GHz) compared to the conventional horn with the same physical size. A simple fabrication process using a 3D printer is introduced, and has been successfully applied. This result represents a remarkable achievement in this field, and may enable a comprehensive solution for satellite and radar systems as a high gain, compact, light-weighted, broadband radiator.

A Metamaterial Loaded Microstrip Patch Antenna for Lower 5G U-NII Spectrum

In this study, we have proposed a metamaterial loaded microstrip patch antenna for the sub-6 GHz range to operate in the Unlicensed National Information Infrastructure (U-NII) band. The Proposed Microstrip Patch Antenna (PMPA) has a U-shaped patch and an array of Complementary Split Ring Resonators (CSRR) in the ground plane. By adding a slot in the middle, the rectangular patch becomes a U-shaped one which is responsible for the enhancement of antenna bandwidth and gain. Our antenna provides a bandwidth of 392 MHz which is about 2.7 times larger compared to that of a Conventional Microstrip Patch Antenna (CMPA) of the same dimension. The maximum gain of our antenna is found 6.56 dB which is around 2 dB higher than that of the conventional one (4.72 dB). Due to the addition of the CSRR array in the ground plane, an improved impedance matching of 50 ohms has been achieved. The operating frequency range of the PMPA is from 5.525 to 5.917 GHz which can be used for 5G applications such as Wi-fi, Wi-Max, and IoT devices in the U-NII band.

Design and analysis of ultrathin X‐band frequency selective surface structure for gain enhancement of hybrid antenna

A wideband ultrathin frequency selective surface (FSS) structure is designed and developed for the complete X-band. The design employs a metallic tetra-arrow (two bidirectional arrows placed diagonally) and a circular split structure (metallic) in the top side and bottom side of RT duroid 5880LZ low-loss substrate respectively. The proposed design has novel contribution in terms of significant reduction in electrical thickness (0.007λ0 which is corresponding to lowest operating frequency, 8.3 GHz) and wider transmission (S21) bandwidth (measured: S21 ≤ − 10 dB, 8.15-13.2 GHz, 47.3%), covering entire X-band due to cumulative loading of surface mount chip resistors in the top layer. The principle of operation of the proposed FSS further can be justified with its equivalent transmission line circuit model, which is based on microwave filter (band-stop and band-pass) topology for anticipating the desired characteristics. The FSS structure is further integrated with dielectric resonator (DR)-slot hybrid antenna for enhancing the gain (measured: peak gain of 4.5 dBi without FSS and 7.8 dBi with FSS) of the antenna. The proposed FSS structure is fabricated and measured performance has very similar responses as simulated ones.