Upper Band Research Articles

Wideband THz antenna using graphene based tunable circular reactive impedance substrate

This letter presents a graphene–based tunable circular reactive impedance substrate (G–CRIS) operating at THz frequency. The proposed RIS is composed of sectoral graphene patch elements, arranged in two concentric rings and printed over silicon dioxide layer which is backed by a thin gold layer. The reactive behavior of the CRIS is made tunable by applying different chemical potential on graphene patches. This tunable CRIS is employed further to improve the operational bandwidth of a THz antenna. The CRIS loaded antenna exhibits miniaturized resonance at the lower band and wideband characteristics at the upper band. Both gain and efficiency of the antenna have been studied throughout the operating band. It is found that at THz frequency this graphene–based RIS is more suitable than metallic RIS for controlling the operational bandwidth.

A Miniaturized Extremely Close-Spaced Four-Element Dual-Band MIMO Antenna System With Polarization and Pattern Diversity

We propose a miniaturized design of a four-element dual-band multiple-input–multiple-output (MIMO) antenna system. The dual-band function is obtained by etching an “L” slot in the radiating patch. The edge-to-edge elements spacing is only 0.023 λ0 . A decoupling structure consisting of cross-shaped metal strips shorted to the ground plane using vias is first introduced. Then, metalized walls are used to enhance the isolation level by realizing the pattern diversity. The measured resonant frequencies are centered at 3.5 and 5.7 GHz with bandwidths of 58 and 43 MHz, peak gains of 2.7 and 2.85 dBi, and peak efficiencies of 63% and 65%, respectively. A considerable measured mutual coupling reduction of 10.8 dB in the lower band and 15.6 dB in the upper band is realized. The overall size of the design is 0.41λ0 × 0.41λ0 × 0.04λ0 with minimum isolation levels of 18.4 and 22.7 dB in the lower and upper bands, respectively. The envelope correlation coefficient is lower than 0.08 across both operating bandwidths. The measured results validate the good diversity performance of the MIMO system.

A Precise Harmonic Control Technique for High Efficiency Concurrent Dual-Band Continuous Class-F Power Amplifier

In this paper, a design approach for a high-efficiency concurrent dual-band power amplifier (PA) with precise harmonic control up to third order is proposed. With the precise harmonic control approach, the high-efficiency performance of the PA can be improved at two arbitrary wide interval frequencies. Based on the inherent impedance matching flexibility of the continuous Class-F (CCF) operating mode, the design spaces of fundamental and harmonic impedances of the PA are largely expanded. The optimal impedances of a CCF PA mode at the internal current-generator (I-gen) plane and package plane are investigated, respectively, and a novel dual-band matching network topology is designed to simultaneously present required load impedances at the fundamental and harmonic impedances of both operation frequencies. First, a harmonic control network is designed to control the harmonic impedances precisely for CCF operation. Then, the fundamental impedances are synthesized using the real frequency technique. To verify the validity of proposed methodology, a dual-band CCF PA operating at 2.6 and 3.5 GHz is designed, fabricated, and measured. The measurement results show that the peak drain efficiency is 76.7% with an output power 42.4 dBm at the lower band and 72.8% with an output power 41.1 dBm at the upper band.

Sumoylation of histone deacetylase 1 regulates MyoD signaling during myogenesis

Sumoylation, the conjugation of a small ubiquitin-like modifier (SUMO) protein to a target, has diverse cellular effects. However, the functional roles of the SUMO modification during myogenesis have not been fully elucidated. Here, we report that basal sumoylation of histone deacetylase 1 (HDAC1) enhances the deacetylation of MyoD in undifferentiated myoblasts, whereas further sumoylation of HDAC1 contributes to switching its binding partners from MyoD to Rb to induce myocyte differentiation. Differentiation in C2C12 skeletal myoblasts induced new immunoblot bands above HDAC1 that were gradually enhanced during differentiation. Using SUMO inhibitors and sumoylation assays, we showed that the upper band was caused by sumoylation of HDAC1 during differentiation. Basal deacetylase activity was not altered in the SUMO modification-resistant mutant HDAC1 K444/476R (HDAC1 2R). Either differentiation or transfection of SUMO1 increased HDAC1 activity that was attenuated in HDAC1 2R. Furthermore, HDAC1 2R failed to deacetylate MyoD. Binding of HDAC1 to MyoD was attenuated by K444/476R. Binding of HDAC1 to MyoD was gradually reduced after 2 days of differentiation. Transfection of SUMO1 induced dissociation of HDAC1 from MyoD but potentiated its binding to Rb. SUMO1 transfection further attenuated HDAC1-induced inhibition of muscle creatine kinase luciferase activity that was reversed in HDAC1 2R. HDAC1 2R failed to inhibit myogenesis and muscle gene expression. In conclusion, HDAC1 sumoylation plays a dual role in MyoD signaling: enhancement of HDAC1 deacetylation of MyoD in the basally sumoylated state of undifferentiated myoblasts and dissociation of HDAC1 from MyoD during myogenesis.

High efficiency slotted photonic crystal waveguides for the determination of gases using mid-infrared spectroscopy

ABSTRACTWe present the design and analysis of a high efficiency slotted photonic crystal waveguide for gas sensing applications in the mid-infrared wavelength range. We designed the slotted photonic crystal waveguide structure by engineering the interfaces between the input and output slot waveguides and a resonant coupler. Coupling and transmission spectra of the sensor have been modeled using the three-dimensional finite-difference time domain method. The sensing principle is based on the shift of the upper band edge of the sensor output transmission spectrum which arises due to changes in the ambient refractive index. Transmission spectrum and sensitivity of the proposed sensor are analyzed by tuning the radii of the air holes localized on each side of the slot. The results show that a change of the refractive index of the gas by 10−4 leads to a shift of the upper band edge wavelength by 540 pm which corresponding to a sensitivity of 1720 nm per refractive index unit. The proposed design may be an ideal platform for developing mid-infrared gas sensing devices characterized by high coupling efficiencies and high sensitivities.

A dual-band CP dual-orthogonal arms monopole antenna with slanting edge DGS for C-band wireless applications

This communication describes a novel design of circularly-polarized (CP) monopole antenna for dual-band performance. The proposed design offers an impedance bandwidth (IBW) of 3.7 GHz in the frequency range 2.9–6.6 GHz in the lower band and 1 GHz (7.7–8.7 GHz) in the upper band. Proposed antenna has a wide CP (3 dB axial-ratio) bandwidth of 2.42 GHz (46.6%) in lower band (4.08–6.5 GHz) and 300 MHz in upper frequency band (8.1–8.4 GHz). The CP bandwidth is achieved through dual orthogonal arms and slanting edge defected ground structure (DGS). Proposed antenna is suitable for the C-Band wireless applications including WLAN, Wi-MAX communication systems.

Dual-band Circularly Polarized Four-arm Spidron Fractal Antenna for Ku-band Satellite Communication

ABSTRACTA dual-band circularly polarized four-arm Spidron fractal antenna is proposed for Ku-band satellite communication. The dual-band characteristic is realized using two-crossed dipole antennas of different lengths. Each dipole arm includes a Spidron fractal patch to generate circular polarization and a printed meander-line to reduce the size. The proposed antenna is fed by a 50- coaxial cable, and a conducting cavity is utilized to obtain a directional circularly polarized radiation pattern. The experiments demonstrate that the fabricated antenna exhibits −10 dB reflection bandwidths ranging from 10.75 GHz to 12.65 GHz and from 13.33 GHz to more than 15 GHz with a broad 3 dB axial ratio bandwidth covering a frequency range of 10.66–14.46 GHz. The measured peak gains are 8.76 dBic in the lower band and 7.43 dBic in the upper band.

Dual-Band Magnetoelectric Dipole Antenna With Dual-Sense Circularly Polarized Character

In this paper, a dual-band dual-sense circularly polarized (CP) magnetoelectric dipole antenna is proposed. The antenna consists of a cavity reflector, two pairs of vertical and horizontal copper plates, and a crossed $\Gamma $ -shaped feeding structure. The shorted vertical plates work as quasi-magnetic dipoles (M-dipoles), while the connected horizontal plates work as electric dipoles (E-dipoles). Two M-dipoles and E-dipoles are designed to possess different heights and lengths, and thus they are able to achieve separate operation bands. To generate dual-sense CP performance, the M-dipoles and E-dipoles are placed in parallel and the adjacent E-dipoles extend along the opposite directions. Benefiting from the intrinsic 90° phase difference between the M-dipole and E-dipole, the left-hand CP is achieved within the lower operation band (2.15–3.4 GHz) and the right-hand CP is achieved within the upper band (4–6.3 GHz). The proposed antenna possesses a unidirectional radiation pattern with high front-to-back ratio ( $\ge 22$ dB). Furthermore, high gain ( $\ge 8$ dBi) and radiation efficiency ( $\ge 90$ %) are also achieved.

Revealing the Nitridation Effects on GaN Surface by First-Principles Calculation and X-Ray/Ultraviolet Photoemission Spectroscopy

In this paper, we report a systematic study of the nitridation effects on GaN surface by first-principles calculations and X-ray/ultraviolet photoemission spectroscopy (XPS/UPS). According to the calculated electronic structures, two surface bands (i.e., the upper band and the lower band) can be seen within the bandgap for the typical surface configurations that may occur in the experimental condition as a result of surface reconstruction. By the deployment of sufficient nitridation, the energy positions of the lower band are modified toward the valence band by ~1 eV, resulting in the overlapping of the lower surface band with the valence band. Meanwhile, the upper surface band is also modified toward the valence band, but by a smaller amount. The modification to the positions of the surface bands is furthermore manifested by XPS/UPS spectra characterization performed on GaN sample that underwent surface treatment with low-energy remote N2 plasma. The theoretical and experimental results insightfully proclaim the nitridation effects on material properties at atomic level, and support a surface-state ionization model for the GaN band-edge (3.4 eV) emission in metal-AlGaN/GaN Schottky-on-heterojunction diode under forward bias.

Offset Aperture-Coupled Double-Cylinder Dielectric Resonator Antenna With Extended Wideband

A compact dielectric resonator antenna for ultrawideband vehicular communication applications is proposed. Two cylindrical dielectric resonators are asymmetrically located with respect to the center of an offset rectangular coupling aperture, through which they are fed. Optimizing the design parameters results in an impedance bandwidth of 21%, covering the range from 5.9 to 7.32 GHz in the lower band and a 53% relative bandwidth from 8.72 to 15 GHz in the upper band. The maximum achieved gain is 12 dBi. Design details of the proposed antenna and the results of both simulations and experiment are presented and discussed.

A new compact CPW-Fed dual-band monopole antenna for RFID applications

<p>This paper presents a study of a new dual-band monopole antenna fed by a Coplanar Waveguide (CPW) line suitable for Radio Frequency Identification (RFID) applications especially designed for RFID readers and covering free ISM bands of 2.45GHz and 5.8GHz. The proposed antenna benefits from the advantages of the CPW line to simplify the structure of the antenna into a single metallic level, by consequent making it easier for integration with microwave integrated circuits. The simulation of the antenna was carried out using ADS from Agilent technologies and CST Microwave Studio electromagnetic solvers. A good impedance bandwidth of 500MHz is achieved in measurement (from 2.1GHz to 2.6GHz for the lower band), while the upper band covers 800MHz (from 5.2GHz to 6GHz). Details of the proposed antenna design and both simulated and experimental results are described and discussed.<strong><em></em></strong></p>

Dual‐band and dual‐polarized antenna with endfire radiation

A novel dual-band endfire antenna with dual polarisation is proposed. The antenna is composed of a shorted metal cavity which functions as a magnetic dipole, a bowtie-shaped electric dipole and an I-shaped resonator (ISR) array. Owing to the combination of complementary dipoles, circularly polarised (CP) electromagnetic waves are generated in the endfire direction at the lower band. A quasi-Yagi antenna structure is adopted to attain broadband linearly polarised (LP) radiation in the upper band. In addition, an ISR structure is loaded to improve the gain in endfire direction. The measured 10-dB impedance bandwidths are 3.93% at the lower band and 29.45% at the upper band, respectively, and the 3-dB axial-ratio bandwidth of 150 MHz (5.76 to 5.91 GHz) is observed in the CP band. Besides, the ISR loaded antenna demonstrates 2-3.5 dB gain improvement over the operational band. This antenna could find applications in radio-frequency identification and indoor positioning systems.

Circularly polarized cylindrical dielectric resonator antenna excited by square ring slot with a T‐shaped microstrip line

AbstractIn this article, a cylindrical dielectric resonator antenna (CDRA) excited by a 45° rotated square ring slot with a T‐shaped coupling microstrip line is investigated for circularly polarized (CP) operation. The proposed antenna shows the dual band characteristics and the lower band is generated due to T‐Shaped microstrip line and upper band is due to CDRA. In the proposed antenna, the two degenerate broadside orthogonal modes ( mode and mode) of the CDRA are used to realize CP radiation. The prototype of the proposed antenna has been fabricated and tested. The measured |S11| bandwidth in the lower and upper band is found to be 14.65 and 19.86%, respectively. The measured 3‐dB axial ratio bandwidth of 1.46 and 6.01% is achieved in the upper band only. Proposed antenna has been found suitable for wireless application.

Reported populations of Meloidogyne ethiopica in Europe identified as Meloidogyne luci.

The tropical group of root-knot nematodes (RKN) including Meloidogyne ethiopica and M. luci is a highly polyphagus and damaging group of agricultural pests. M. ethiopica has been detected in several European countries (Slovenia, Italy, Greece) and also in Turkey. However, a description of a new sister species M. luci calls for reclassification of all European and Turkish M. ethiopica populations reported up to date as M. luci. Accurate identification can be accomplished through analysis of the esterase isozyme pattern, which is the most distinguishing character between the two otherwise very similar species. Both species display a three banded esterase pattern where the upper band is slightly shifted between the two species. In addition, molecular characterization of M. ethiopica and M. luci populations revealed that the ITS, SSU, and LSU of the rDNA regions are not appropriate markers for studying relationships among the tropical group of RKNs. However, the COII/lRNA region on mtDNA proved to be very useful for analyzing the phylogenetic relationship of these very closely related species/populations. Mitochondrial sequences with low levels of heteroplasmy allowed clustering of all M. luci populations in a monophyletic clade with a clear separation of this recently described species from M. ethiopica. At the same time, a very close relationship between M. ethiopica and M. luci was confirmed again.

First report of resonant interactions between whistler mode waves in the Earth's magnetosphere

AbstractNonlinear physics related to whistler mode waves in the Earth's magnetosphere are now becoming a hot topic. In this letter, based on Time History of Events and Macroscale Interactions during Substorms waveform data, we report several interesting whistler mode wave events, where the upper band whistler mode waves are believed to be generated through the nonlinear wave‐wave coupling between two lower band waves. This is the first report on resonant interactions between whistler mode waves in the Earth's magnetosphere. In these events, the two lower band whistler mode waves are observed to have oppositely propagating directions, while the generated upper band wave has the same propagating direction as the lower band wave with the relatively higher frequency. Moreover, the wave normal angle of the excited upper band wave is usually larger than those of two lower band whistler mode waves. Our results reveal the large diversity of the evolution of whistler mode waves in the Earth's magnetosphere.

Concurrent dual‐band digital predistortion implemented with reduced look‐up‐tables

A reduced look-up-tables (LUTs) implementation of digital predistortion (DPD) for concurrent dual-band power amplifiers (PAs) is proposed. In the proposed method, the dual-band output is captured jointly with reduced sampling rate, then the PA characteristics of the lower band and the upper band are identified with a group of shared model coefficients, thus DPD can be implemented with shared LUTs for the two bands, which results in reducing the LUTs by 50% comparing with those traditional dual-band DPD techniques implemented with individual LUTs for each band. Experimental results show that the proposed method can achieve better than −48.2 dBc adjacent channel power ration performance with reduced LUTs.

Low-Profile Dual-Band Pattern Diversity Patch Antenna Based on Composite Right/Left-Handed Transmission Line

A low-profile patch antenna with pattern diversity is proposed. The topology combines an annular ring together with a center-fed circular patch. The composite right/left-handed transmission line is loaded on both the annular ring and the circular patch, to realize the 2.4/3.5-GHz dual-band operation. The outer annular ring works at its first pair of symmetric modes, which results in broadside radiation patterns, while the inner circular patch provides omnidirectional patterns in the horizontal plane, as a consequence of its physical circular symmetry. The field distribution is analyzed to verify the operational principle. By optimizing the feeding network, the antenna reaches a good impedance matching in both bands. A prototype is fabricated, and the measured results agree well with the simulated ones. The measured correlation coefficient is lower than 0.04 and 0.05 in the lower and upper band, respectively.

Dual-Band Dual-Mode Button Antenna for On-Body and Off-Body Communications.

A dual-band dual-mode button antenna for body centric communications is presented. At the lower band, a spiral inverted-F antenna is designed with omnidirectional radiation pattern for on-body communication. At the upper band, the high-order mode of the inverted-F antenna is utilized together with a metal reflector to realize broadside radiation for off-body communication. For demonstration, a prototype is implemented. The measured peak gains on the phantom at the lower and upper bands are -0.6 and 4.3 dBi, respectively. The antenna operating on the phantom has measured efficiencies of 46.3% at the lower band and 69.3% at the upper band. The issue of specific absorption rate (SAR) is studied. The maximum transmitted power under the SAR regulation of 1.6 W/kg is found to be 26.4 dB·m, which is high enough for body centric communications. In addition, the transmission performance between two proposed antennas mounted on the body is investigated by measuring the transmission loss. With an overall miniaturized size, the robust button antenna could be integrated in clothes and be a potential candidate for wireless body area network applications.

A high selective filtering small size/dual band antenna using hybrid terminated modified CRLH cell

AbstractThis article presents a new small size dual band metamaterial antenna. The antenna is realized using a single cell of a suggested modified version of composite right left handed transmission line terminated by a hybrid capacitive loading with short circuit termination. The hybrid termination leads to decrease the size of the antenna whereas the modified composite right left handed cell configuration leads to introduce dual band antenna functionality at 2.5 and 2.92 GHz. The antenna size is only 31 × 26 mm2. Compared to, single band, non‐selective, conventional patch antenna, the size of the proposed antenna is only 9 and 11.5% at the two former frequencies, respectively. Despite the small size, the antenna gain is more than 3.5 dBi at the two operating frequencies. Moreover, the antenna has a high roll off beyond the operating frequency band which leads to high selective characteristics. The antenna can suppress 100% of the nearby signal power beyond its bands by 300 MHz at lower band and 200 MHz at upper band. The antenna design is discussed; the full wave simulation and experimental measurements are introduced for validating the results.

A compact dual-band 2 × 1 metamaterial inspired mimo antenna system with high port isolation for LTE and WiMax applications

This article proposes a compact (43 × 26 × 0.8 mm3) dual-band two-element metamaterial-inspired MIMO antenna system with high port isolation for LTE and WiMAX applications. In this structure, each antenna element consists of a square–ring slot radiator encircling a complementary split ring resonator. A tapered impedance transformer line feeds these radiating apertures and shows good impedance matching. A 2 × 3 array of two-turn Complementary Spiral Resonator structure between the two antenna elements provides high dual-band isolation between them. The fabricated prototype system shows two bands 2.34 – 2.47 GHz (suitable for LTE 2300) and 3.35 – 3.64 GHz (suitable for WiMAX). For spacing between two antennas of 10 mm only, the measured isolation between the two antenna elements in the lower band is around −32 dB while that in the upper band is nearly 18 dB. The system shows a doughnut-shaped radiation patterns. The peak measured antenna gains for the proposed MIMO system in the lower and higher bands are 3.9 and 4.2 dBi, respectively. The MIMO system figure of merits such as the envelope correlation coefficient, total efficiency are also calculated and shown to provide good diversity performance.