Search

In this letter, a low-profile and wideband substrate integrated waveguide (SIW) antenna is proposed and validated for full-duplex systems. The proposed antenna operates at 4.9 GHz and 5.8 GHz Wireless Local Area Network (WLAN) bands. Each resonator of the antenna consists of a modified half-mode SIW (HMSIW) cavity, and excited by a 50 $\Omega$ coaxial probe. The wideband response is achieved by coupling the fundamental TE\textsubscript{10} mode with the perturbed TE\textsubscript{10} mode of the HMSIW cavity. The compactness of the proposed design is obtained using two rectangular slots near the closed-ends of the cavities. By properly optimizing the overall geometry, the proposed design exhibits a 10-dB fractional bandwidth of 8.2 \% (4.78--5.2 GHz) and 7.7 \% (5.70--6.16 GHz) in the lower (4.9 GHz) and upper frequency band (5.8 GHz), respectively. The bandwidths of both frequency bands can be controlled by adjusting the coupling between modes. A high isolation ( $>$ 30 dB) between the two ports is observed due to series of metallic vias between them. This antenna has compact size (0.34 $\lambda_{g}^{2}$ ) with high gains of 5.24 dBi and 5.37 dBi at 4.9 GHz and 5.8 GHz, respectively.

A highly compact substrate integrated waveguide (SIW) self-diplexing antenna, operating at wireless local area network bands (3.6 and 5.4 GHz), is proposed in this letter. The proposed antenna consists of two closely placed (0.022 $\lambda _{g}$ , where $\lambda _{g}$ is the guided wavelength at 3.6 GHz) quarter-mode SIW resonators, exited by two coaxial probes. Two rectangular slots are added to the closed-ends of each resonator to generate additional capacitances. Therefore, both resonators operate below their fundamental frequencies, and hence, miniaturization is achieved. Moreover, a reliable circuit model is developed to validate the design process. The proposed antenna has ultracompact dimensions of 0.08 $\lambda _{g}^{2}$ with simulated gains of 4.9 and 5.34 dBi at 3.6 and 5.4 GHz, respectively. In addition, the simulated isolation levels are 32.5 and 36.6 dB at the lower and higher resonant bands, respectively. Furthermore, both resonant frequencies can be independently controlled by changing the length of the capacitive slots. Due to its compactness, independent resonance control and high isolation, the proposed antenna is suitable for compact and planar radio frequency components.

This article presents a novel terahertz (THz) antenna array design comprising a layered structure of a perovskite material which enhances the radiation characteristics of an antenna overlaid on a conventional metallic antenna element. The simulated antenna consists of a THz gold patch antenna coated with a hybrid perovskite material, methyl-ammonium lead iodide CH3NH3PbI3 which enables the manipulation of the THz electromagnetic waves. In addition to this, we also present a comparison of the antenna properties of the proposed hybrid perovskite material with antennas made of gold and perovskite only. The proposed antenna operates in the frequency band 0.9 - 1.2 THz. The simulated impedance bandwidth of the proposed array antenna ranges from 0.9 THz to 1.2 THz with a reflection coefficient (S11) less than -10 dB. The antenna array has a radiation patterns stability on the whole frequency band. The peak gain obtained is 11.4 dBi with perovskite arrays. The hybrid and perovskite antenna array demonstrate high radiation efficiency. The designs presented here will help in realising future wireless communication systems that require miniaturisation, fast reconfigurability and wearability.

This paper presents a low-profile multiple-input multiple-output (MIMO) implantable antenna system including a capsule endoscopy and a scalp implantation at Medical Implant Communication Service (MICS) band (402–405 MHz), and Industrial, Scientific, and Medical (ISM) band (433.1–438.8 MHz). It consists of two elements with an edge-to-edge gap of 0.0018λg and overall dimensions of π × (5.65)2 × 0.13 mm3 and is placed on a 0.13 mm thick RO3010 (ϵr = 10.2, tanδ = 0.0022) substrate. The antenna is integrated with batteries, sensors, and electronic components in two different types of implantable devices (capsule and flat-type devices). The simulation result shows that the antenna has a fractional bandwidth (FBW) of 33.9%, a maximum realized gain of -30 dBi, and isolation of more than 26 dB. The fabricated prototype is measured in a saline solution and minced pork meat. The measured results are found in good accordance with simulations. The antenna parameters are calculated and showed a significant independence between the radiators. A link budget is estimated to be 78 Mb/s for a distance of 20 meters. Thus, the proposed antenna is considered as a promising solution for high data-rate medical applications such as capsule endoscopy, live surgeries, and other biomedical applications where the high data-rate is required.

A novel millimeter-wave (MMW) hybrid isolator is presented to reduce the mutual-coupling (MC) between two closely-spaced dielectric resonators (DR) antennas at 60 GHz. The proposed hybrid isolator consists of a combination of a new uni-planar compact electromagnetic band-gap (EBG) structure and an MMW choke absorber. The design of the proposed EBG unit-cell is based on the stepped-impedance resonator (SIR) technique. The results show that the proposed EBG structure provides a wide frequency bandgap in the 60 GHz band with miniaturization factors of 0.79 and 0.66 compared to conventional uni-planar EBG and uni-planar compact (UC-EBG) structures, respectively. The proposed EBG is then placed between two Multiple-Input Multiple-Output (MIMO) DR antennas to reduce the MC level. As a result, an average of 7 dB level reduction is obtained. To further reduce the MC level, a thin MMW choke absorber wall is mounted vertically between the two DR antennas and above the EBG structure. An average of 22 dB MC reduction is achieved over the suggested bandwidth while maintaining good radiation characteristics. The measured isolation of the prototype antenna varies from -29 to -49 dB in the frequency range from 59.3 to 64.8 GHz. In fact, the proposed hybrid isolator outperforms other hybrid isolation techniques reported in the literature.

Printed ridge gap waveguide (PRGW) is considered among the state of art guiding technologies due to its low signal distortion and low loss at Millimeter Wave (mmWave) spectrum, which motivates the research community to use this guiding structure as a host technology for various passive microwave and mmWave components. One of the most important passive components used in antenna beam-switching networks is the quadrature hybrid directional coupler providing signal power division with 90° phase shift. A featured design of a broadband and compact PRGW hybrid coupler is propose in this paper. A novel design methodology, based on mode analysis, is introduced to design the objective coupler. The proposed design is suitable for mmWave applications with small electrical dimensions ( $1.2\,\,\lambda _{o} \times 1.2\,\,\lambda _{o}$ ), low loss, and wide bandwidth. The proposed hybrid coupler is fabricated on Roger/RT 6002 substrate material of thickness 0.762 mm. The measured results highlight that the coupler can provide a good return loss with a bandwidth of 26.5% at 30 GHz and isolation beyond 15 dB. The measured phase difference between the coupler output ports is equal $90^\circ \pm ~5^\circ $ through the interested operating bandwidth. A clear agreement between the simulated and the measured results over the assigned operating bandwidth has been illustrated.

In this paper, a 1-bit, high gain and wide-band reflectarray metasurface is proposed. The proposed reflectarray operates from 0.9 THz to 1.4 THz giving operational bandwidth of 0.5 THz. The realized gain achieved is 32 dB at 1.4 THz while the maximum simulated aperture efficiency is calculated to be 55%. The reflectarray is designed on polyimide substrate with permittivity of 3.48 and loss tangent of 0.03 at THz frequencies. The dimension of the metasurface is $3\times 3\ \text{mm}^{2}$ and contains 3904 patch elements illuminated by a THz horn antenna. With high gain and flexible nature of the polyimide, the proposed metasurface is also suitable for wearable application.

This paper proposes a novel 1-bit, electronically reconfigurable, subwavelength metasurface unit cell for sub-6 GHz applications. 180° phase shift is achieved by integrating a single PIN diode in the structure. The unit cell incorporates three layers: The top layer is used for wave reflection, the bottom layer is used for PIN diode placement and DC biasing, and the middle layer acts as a ground plane. The resonance of the unit cell is kept around 3.3 GHz. The magnitude of the reflection coefficient is above 90%. Besides, a phase difference of 180°+20° is achieved over 200 MHz bandwidth. With these characteristics, the proposed unit cell can find its applications in programmable metasurface functions such as beam steering, beam focusing and beam scattering.

Graphene devices have been widely explored for photonic applications, as they serve as promising candidates for controlling light interactions resulting in extreme confinement and tunability of graphene plasmons. The ubiquitous presence of surface crumples in graphene, very less is known on how the crumples in graphene can affect surface plasmon resonance and its absorption properties. In this article, a novel approach based on the crumpled graphene is investigated to realize broadband tunability of plasmonic resonance through the mechanical reconfiguration of crumpled graphene resonators. The mechanical reconfiguration of graphene crumples combined with dual electrostatic gating (i.e. raising the Fermi level from 0.2–0.4 eV) of graphene serves as a tuning knob enabling broad spectral tunability of plasmonic resonance in the wavelength range of 14–24 µm. The crumpled region in the resonators exhibits an effective trapping potential where it extremely confines the surface plasmonic field on the surfaces of crumples providing localized surface plasmon resonance at the apices of these crumples. Finally, to achieve near-unity absorption >99% at the resonance wavelengths (17 µm and 22 µm) crumpled graphene resonators are loaded with four ring shaped metamaterials which result in the enhanced near-field intensity of ≈1.4×106. This study delivers insight into the tunability of crumpled graphene and their coupling mechanism by providing a new platform for the flexible and gate tunable graphene sensors at the infrared region.

In this paper, A miniaturized dual-band implantable antenna using meandered line resonator is proposed for bio-telemetry applications. The proposed antenna has dual-band (0.91 GHz and 2.45 GHz) operation, covering the important Industrial, Scientific and Medical (ISM) bands. Miniaturization is achieved using meandered resonator and a square slot etched in the ground plane. The performance of the proposed antenna inside a quasi-implantable biomedical device (IBD) is analysed in a homogeneous skin model, human intestine and human head. The measurements are performed by implanting the quasi-IBD inside a saline solution and minced pork meat. The quasi-IBD consists of the proposed antenna, batteries and printed circuit board (PCB) with electronic components on it. The proposed antenna has compact dimensions of 5.6 × 5 . 8 × 0.25 mm3. The measured peak gains in the minced pork meat are −22.9 dBi and −22.1 dBi at 0.91 GHz and 2.45 GHz, respectively. The low specific absorption rate (SAR) of the proposed antenna allows maximum input power of 3.32 mW at 0.91 GHz and 4.37 mW at 2.45 GHz. To the best of the authors’ knowledge, this is the most compact dual-band implantable antenna reported in the literature for 0.91 GHz and 2.45 GHz ISM bands.

A new millimeter-wave (MMW), electromagnetic band-gap (EBG) structure is presented. The proposed EBG structure without the use of metallic vias or vertical components is formed by etching two slots and adding two connecting bridges to a conventional uniplanar EBG unit-cell. The transmission characteristics of the proposed EBG structure are measured. Results show that the proposed EBG structure has a wide bandgap around the 60 GHz band. The size of the proposed EBG unit-cell is 78% less than a conventional uniplanar EBG, and 72% less than a uniplanar-compact EBG (UC-EBG) operating at the same frequency band. Moreover, and despite the fabrication limitations at the 60 GHz band, the proposed EBG unit-cell provides at least 12% more size reduction than any other planar EBG structures at microwave frequencies. Its enhanced performance and applicability to reduce mutual coupling in antenna arrays are then investigated. Results show a drastic decrease in the mutual coupling level. This EBG structure can find its applications in MMW wireless communication systems.

Design, fabrication and testing of millimeter-wave (MMW) dielectric resonator antenna (DRA) surrounded by electromagnetic band-gap (EBG) structure are presented. For this purpose, MMW mushroom-like, circular patch EBG (CP-EBG) cell is designed and fabricated. The propagation characteristics of the proposed CP-EBG structure are measured using the asymmetric microstrip line method. A cylindrical DRA incorporating the developed CP-EBG structure is then designed and its performance is evaluated with and without the CP-EBG around the 60 GHz bandwidth. Measurements show a significant improvement in the antenna radiation characteristics when it is surrounded by CP-EBG structure. A gain increase of up to 3.2 dBi is obtained while preserving the gain flatness over the suggested bandwidth ( ± 0.7 dB). An additional backlobe suppression of up to 6.5 dBi is achieved. Moreover, radiation toward substrate edges is significantly reduced.

Design and analysis of millimeter-wave (MMW) mushroom-like, circular-patch electromagnetic band-gap (EBG) structure is presented. The in-phase reflection and band-gap characteristics of the proposed EBG structure are investigated. Results show that the proposed EBG structure has stable reflection properties when normally and obliquely illuminated by a plane wave with different polarizations around the 60 GHz band. In addition, the proposed EBG structure is found to have a band-gap around the same frequency bandwidth. With these properties, proposed EBG structure is suitable to be used as reflectors in antenna applications in orderto increase the gain and improve the radiation characteristics.

A new uni-planar compact electromagnetic bandgap (EBG) structure is presented. The proposed EBG unit-cell is designed based on the stepped-impedance resonator (SIR) technique. Results show that the proposed EBG structure provides a wide frequency bandgap around the 60 GHz band. Moreover, results show that the proposed EBG unit-cell has further miniaturization factors of 0.79 and 0.66 compared to conventional uni-planar EBG and uniplanar compact (UC-EBG) structures, respectively.

A new 60 GHz hybrid isolator is presented and incorporated to efficiently reduce mutual coupling in a closely-spaced dielectric-resonator (DR) antenna array. The hybrid isolator comprises a new compact uni-planar electromagnetic bandgap (EBG) structure and two millimeter-wave (MMW) absorber walls. Simulated results show the effectiveness of the proposed hybrid isolator for reducing the mutual coupling level without disturbing the radiation characteristics. Finally, with the easy-to-fabricate EBG structure, as well as the low cost MMW absorber, the proposed hybrid isolator is suitable to be used in MMW wireless communication systems.

A new millimeter-wave (MMW), frequency-selective surface (FSS) unit-cell is presented. The reflection and transmission characteristics of the proposed FSS structure are investigated. Results show that by using only one PIN diode in each unit-cell, the transmissive/reflective bands can be altered. The proposed FSS is then incorporated as in MMW aperture-coupled dielectric resonator (DR) antenna to achieve beam steering and pattern diversity. By sequentially biasing the diodes, beam steering can be achieved along the entire azimuth plane. Moreover, by configuring the states of the diodes, directional and Omni-like patterns can be obtained.

A millimeter-wave (MMW) electromagnetic band-gap (EBG)-based dielectric resonator antenna (DRA) array with reduced mutual coupling is presented. For this purpose, a new compact MMW electromagnetic band-gap (EBG) structure is designed. The stopband characteristics of the proposed EBG structure are investigated. The performance of two-element cylindrical DRA array incorporating the developed EBG structure is then evaluated with and without the EBG structure. Results show a significant in the mutual coupling when the EBG structure is inserted between the array elements. With these characteristics, this antenna array can be used in MMW wireless communication systems.

Millimeter-wave (MMW) electromagnetic bandgap (EBG)-based dielectric resonator (DR) antenna with beam steering capability is presented. Six EBG sectors of several cells are placed symmetrically around the DR antenna to achieve beam steering in the azimuth plane. Each sector is composed of twenty one circular-patch mushroom EBG unit cell. The vias in each sector are connected through thin metallic veins printed on a conductor-backed dielectric slab. The metallic veins are then connected to the ground plane through a switching diode. By switching the diode on and off, the EBG sector band-stop and band-pass properties are changed, yielding beam steering into that sector. Results show flexible and effective beam steering capability in the azimuth plane using minimal number of diodes.

In this paper, a millimeter-wave aperture-coupled dielectric resonator antenna (ACDRA) with low back radiation is presented. Back radiation reduction was achieved through a circular patches-mushroom like EBG structure placed underneath the antenna. Simulated results show 18 dB improvements in the backward radiation compared to the case where no EBG is used.

In this paper, the design of a uniplanar-compact electromagnetic band-gap (UC-EBG) aperture coupled millimeter-wave dielectric resonator antenna on low temperature co-fired ceramics (LTCC) dense substrate is presented. The simulated results for the antenna with and without the UC-EBG are discussed to show the advantages coming from the use of UC-EBG. Using this approach, a new UC-EBG dielectric resonator antenna was designed and simulated. The obtained results show good performance in terms of back-lobe radiation reduction.