scholarly journals Complex shaped periodic corrugations for broadband Bull’s Eye antennas

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Despoina Kampouridou ◽  
Alexandros Feresidis
Keyword(s):  
Gain Bandwidth ◽  
Maximum Value ◽  
Low Profile ◽  
Unit Cells ◽  
Periodic Rings ◽  
Novel Complex ◽  
Flat Gain ◽  
Periodic Configuration ◽  
Bull's Eye ◽  
First Time

AbstractPeriodically corrugated metallic antennas have been developed in recent years from microwave to THz frequencies, due to their advantages of highly directive radiation patterns, low profile and ease of fabrication. However, the limited gain bandwidth of such antennas remains one of their inherent disadvantages. In terms of design, the majority of the existing implementations in literature utilize the standard rectangular shaped corrugated unit cell. In this paper, we propose novel complex shaped corrugated unit cells that produce a broadband performance when assembled in a periodic configuration. Two broadband prototypes are presented at the Ku frequency band that are formed of hybrid shaped corrugations. The first prototype of six periodic rings achieves, for the first time, a flat gain simulated response with a maximum value of 15.7 dBi, 1-dB gain bandwidth of 16.4%, and an extended 3-dB gain bandwidth of 19.64%. The second novel prototype of five rings achieves an enhanced 3-dB gain bandwidth of 15.2% and maximum gain of 18.1 dBi.

scholarly journals High Piezoelectric Conversion Properties of Axial InGaN/GaN Nanowires

2018 ◽  
Author(s):  
Nikoletta Jegenyes ◽  
Martina Morassi ◽  
Pascal Chrétien ◽  
Laurent Travers ◽  
Lu Lu ◽  
...  
Keyword(s):  
State Of The Art ◽  
Electrical Energy ◽  
Piezoelectric Response ◽  
Average Output ◽  
Gan Nanowires ◽  
Piezoelectric Energy ◽  
Atomic Force ◽  
Maximum Value ◽  
Promising Perspective ◽  
First Time

We demonstrate for the first time efficient mechanical to electrical energy conversion using InGaN/GaN nanowires (NWs). Using an atomic force microscope equipped with a modified Resiscope module, we analyse the piezoelectric energy generation of GaN NWs and demonstrate an important enhancement when integrating in their volume a thick In-rich InGaN insertion. The piezoelectric response of InGaN/GaN NWs can be tuned as a function of the InGaN insertion thickness and position in the NW volume. The energy harvesting is favoured by the presence of a PtSi/GaN Schottky diode which allows to efficiently collect the piezo-charges generated by InGaN/GaN NWs. Average output voltages up to 330 ± 70 mV and a maximum value of 470 mV per NW has been measured for nanostructures integrating 70 nm-thick InGaN insertion capped with a thin GaN top layer. This latter value establishes an increase of about 35% of the piezo-conversion capacity in comparison with binary p-doped GaN NWs. By considering these output signals, we estimate a maximum power density generated by one layer of dense InGaN/GaN-based NW of about 3.3 W/cm2. These results settle the new state-of-the-art for piezo-generation from GaN-based NWs and offer a promising perspective for extending the performances of the piezoelectric sources.

scholarly journals Анизотропия анионной проводимости в монокристаллах суперионного проводника CeF-=SUB=-3-=/SUB=-

2021 ◽  
Vol 63 (9) ◽  
pp. 1376
Author(s):  
Н.И. Сорокин ◽  
В.В. Гребенев ◽  
Д.Н. Каримов
Keyword(s):  
Electrical Conductivity ◽  
Atomic Structure ◽  
Unit Cell ◽  
Conductivity Measurements ◽  
Weak Anisotropy ◽  
Tysonite Structure ◽  
Maximum Value ◽  
Anisotropy Effect ◽  
First Time ◽  
Anionic Conductivity

The anisotropy of anionic conductivity in crystals of a superionic conductor CeF3 with the tysonite structure (sp. gr. P-3с1) has been studied for the first time. The conductivity measurements at temperatures from 300 K to 600 K were carried out along the principal a- and c-axes of trigonal unit cell of the crystal. The maximum value of electrical conductivity is observed along the c-axis. The superionic CeF3 crystals have the weak anisotropy of electrical conductivity equal to σ||c/σ||a = 2.4 and σ||c = 5.6 10–4 S/cm at 500 K. The anisotropy effect of anionic conductivity in individual fluorides with the tysonite structure is discussed in connection with the peculiarities of their atomic structure.

scholarly journals Millimeter Wave Fabry-Perot Resonator Antenna Fed by CPW with High Gain and Broadband

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Xue-Xia Yang ◽  
Guan-Nan Tan ◽  
Bing Han ◽  
Hai-Gao Xue
Keyword(s):  
Millimeter Wave ◽  
Coplanar Waveguide ◽  
Dielectric Substrate ◽  
High Gain ◽  
Center Frequency ◽  
Impedance Bandwidth ◽  
Gain Bandwidth ◽  
Broad Bandwidth ◽  
Low Profile ◽  
Fabry Perot

A novel millimeter wave coplanar waveguide (CPW) fed Fabry-Perot (F-P) antenna with high gain, broad bandwidth, and low profile is reported. The partially reflective surface (PRS) and the ground form the F-P resonator cavity, which is filled with the same dielectric substrate. A dual rhombic slot loop on the ground acts as the primary feeding antenna, which is fed by the CPW and has broad bandwidth. In order to improve the antenna gain, metal vias are inserted surrounding the F-P cavity. A CPW-to-microstrip transition is designed to measure the performances of the antenna and extend the applications. The measured impedance bandwidth ofS11less than −10 dB is from 34 to 37.7 GHz (10.5%), and the gain is 15.4 dBi at the center frequency of 35 GHz with a 3 dB gain bandwidth of 7.1%. This performance of the antenna shows a tradeoff among gain, bandwidth, and profile.

scholarly journals Innovative Reconfigurable Metasurface 2-D Beam-Steerable Reflector for 5G Wireless Communication

Electronics ◽  
2020 ◽  
Vol 9 (8) ◽  
pp. 1191
Author(s):  
David Rotshild ◽  
Efraim Rahamim ◽  
Amir Abramovich
Keyword(s):  
Beam Steering ◽  
Unit Cell ◽  
Reflection Phase ◽  
Low Profile ◽  
Unit Cells ◽  
Phase Range ◽  
New Type ◽  
Dc Bias ◽  
Communication Methods ◽  
Indoor And Outdoor

A tunable reflector component based on metasurface (MS) with a low profile and reduced mass is offered for indoor and outdoor 5G communication methods to overcome obstacles such as buildings, walls, and turns, and to allow wireless quasi-line of sight path communication at 37 GHz. Integrating varactors with MS unit cells allows tunability and reconfigurability. This approach was presented in many studies, with frequencies of up to K–band. However, today, higher frequencies are used, especially in communication. This work presents the design of a reconfigurable MS reflector, at Ka-band frequencies, based on a new type of resonant unit cell, with uniformed reflection for wide-incident-angular-range, and a simple stimulating DC bias for each MS unit cell, which allows a two–dimensional (2-D) continuous reflection phase manipulation. The unit cell provides a dynamic reflection phase range of over 300° at a wide bandwidth. Simulations of one-dimensional (1-D) and (2-D) at 37 GHz are presented. A steering range of up to ±48° was obtained for azimuth or elevation. A simultaneous independent 2-D beam steering range of up to ±10° in azimuth and up to ± 5° in elevation, allowing obstacles to overcome covering at a practical angular spatial cone of 20° and 10°, is presented.

scholarly journals Tunable Duplex Metalens Based on Phase-Change Materials in Communication Range

Nanomaterials ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 993 ◽  
Author(s):  
Wei Bai ◽  
Ping Yang ◽  
Shuai Wang ◽  
Jie Huang ◽  
Dingbo Chen ◽  
...  
Keyword(s):  
Phase Change ◽  
Phase Change Material ◽  
Phase Change Materials ◽  
Three Dimensional ◽  
Special Unit ◽  
Compact Size ◽  
Unit Cells ◽  
First Time ◽  
Change Material ◽  
Different Sources

Metalenses recently have attracted attention because of their more compact size in comparison with conventional lenses; they can also achieve better optical performance with higher resolution. Duplexer is an interesting function of a metalens that can distinguish different sources and divide them into two parts for specific purposes. In this article, we design tunable duplex metalenses with phase-change material Ge2Sb2Te5 for the first time. Two types of special unit cells are designed to modulate the incident lights, and four metalenses are designed based on the two types of unit cells. Specific phase profiles are calculated for different sections of metalens in which the corresponding unit cells are settled; accordingly, the metalenses can focus the incident lights at any positions according to our design. Moreover, the metalenses become selectable via tuning the state of phase-change material, which means that the output light field can be actively controlled. The proposal of our tunable duplex metalenses will offer new opportunities for active three-dimensional imaging or optical coding.

scholarly journals Contrast sensitivity and behavioural evidence for lateral inhibition in octopus

2019 ◽  
Vol 15 (5) ◽  
pp. 20190134 ◽  
Author(s):  
Luis Nahmad-Rohen ◽  
Misha Vorobyev
Keyword(s):  
Spatial Frequency ◽  
Contrast Sensitivity ◽  
Lateral Inhibition ◽  
Neural Processing ◽  
Visual Systems ◽  
Maximum Value ◽  
Fixation Reflex ◽  
First Time ◽  
The Brain ◽  
Behavioural Evidence

Behavioural contrast sensitivity in Octopus tetricus was measured in the range of 0.05–12 cycles per degree (cpd) using a fixation reflex. We show that the contrast sensitivity reaches its maximum (between 1 and 4%) at 0.3 cpd, and decreases to approximately half of the maximum value at the lowest spatial frequency. Reduction of sensitivity at low spatial frequency is a signature of lateral inhibition in visual systems. In vertebrates and insects, lateral inhibition helps to overcome the bottleneck of encoding information into spikes. In octopus, photoreceptors generate spikes themselves and are directly connected to the brain through their axons. Therefore, the neural processing occurring in the octopus brain cannot help overcome the bottleneck of encoding information into spikes. We conclude that, in octopus, either the lateral inhibition occurs in the brain after information has been encoded into spikes, or photoreceptors inhibit each other. This is the first time behavioural contrast sensitivity has been measured in a cephalopod.

Soil gas CO2 emissions and fault locking along the Anninghe fault and the Zemuhe fault, in China Seismic Experimental Site

2020 ◽  
Author(s):  
Ying Li ◽  
Yao Yang ◽  
Zhi Chen
Keyword(s):  
Active Faults ◽  
Soil Gas ◽  
Dislocation Model ◽  
Experimental Site ◽  
Maximum Value ◽  
High Level ◽  
Fault Locking ◽  
First Time ◽  
Northern Segment ◽  
Anninghe Fault

<p>The Anninghe fault (ANHF) and the Zemuhe fault (ZMHF) with high level of seismic hazards in the China Seismic Experimental Site, located in southeastern of Tibet, are some of the most active faults in China. Measurement of the soil gas CO<sub>2</sub> has been conducted in three sites along the ANHF and the ZMHF for the first time. Totally, 394 sampling points along 15 profiles were measured. The fault locking degree of different segments of the ANHF and the ZMHF were inverted by the negative dislocation model using GPS velocity data  since 2013 to 2017. The measurements results show that the average and maximum value of CO<sub>2</sub> in the ZMHF is significantly higher than that in the ANHF. Soil gas CO<sub>2</sub> geochemistry yielded different spatial anomalous features, indicating the different properties and permeability of the faults. The inversion results reveal that the level of coupling including the locking depth and intensity along the southern segment of the ANHF was significantly larger than the northern segment of the ZMHF. Combining the CO<sub>2</sub> emission results, we concluded that the intensive locking of the segments reduced their permeability due to the self-sealing process, results in less gas to escape from the deep. Correspondingly, the creeping fault with low level of coupling can maintain high permeability which is more favorable to gas CO<sub>2</sub> migration.</p>

scholarly journals Growth and Neutron Diffraction Investigation of Ca3NbGa3Si2O14 and La3Ga5.5Nb0.5O14 Crystals

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
I. A. Kaurova ◽  
G. M. Kuz’micheva ◽  
V. B. Rybakov ◽  
A. Cousson ◽  
O. Zaharko ◽  
...  
Keyword(s):  
Solid State ◽  
Neutron Diffraction ◽  
Solid State Reaction ◽  
Oxygen Vacancies ◽  
Czochralski Technique ◽  
Conventional Solid State Reaction ◽  
Growth Atmosphere ◽  
Unit Cells ◽  
The Difference ◽  
First Time

Langanite (La3Ga5.5Nb0.5O14, growth atmosphere: 99% Ar + 1% O2) and kanigasite (Ca3NbGa3Si2O14, growth atmosphere: 100% Ar) crystals grown by the Czochralski technique in Ir crucibles along <0001> direction have been firstly investigated by neutron diffraction. The difference between the compositions of upper (La2.935(2)□0.065)(Ga0.450Nb0.550(3))Ga3(Ga1.965(4)□0.035)(O13.90(1)□0.10) and lower (La2.940(1)□0.060)(Ga0.590Nb0.410(2))Ga5(O13.82(1)□0.18) parts of orange langanite crystal was found. It was established that the colorless Ca3NbGa3Si2O14 crystal grown by using the single-crystal charge has the composition (Ca2.95□0.05(1))NbGa3Si2O14 and is less defective in comparison to the yellow one grown by using the charge prepared by conventional solid-state reaction. For Ca3NbGa3Si2O14 and La3Ga5.5Nb0.5O14 crystals the possibility of microtwin formation (two unit cells connected by the translation: 1/2 z) was revealed for the first time. It was found that the difference between the color of crystals is attributed to the qualitative differentiation of oxygen vacancies.

scholarly journals A Compact, Low-Profile Log-Periodic Meandered Dipole Array Antenna with an Artificial Magnetic Conductor

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Oh Heon Kwon ◽  
Sungwoo Lee ◽  
Jong Min Lee ◽  
Keum Cheol Hwang
Keyword(s):  
Ground Plane ◽  
Array Antenna ◽  
Main Beam ◽  
Beam Direction ◽  
Magnetic Conductor ◽  
Artificial Magnetic Conductor ◽  
Line Configuration ◽  
Low Profile ◽  
Unit Cells ◽  
Meander Line

A compact and low-profile log-periodic meandered dipole array (LPMDA) antenna with an artificial magnetic conductor (AMC) is proposed. For compactness, a meander line configuration is implemented with dipole elements and optimized using a genetic algorithm (GA) to realize the LPMDA antenna. As a result, a size reduction of approximately 30% is achieved as compared to a conventional log-periodic dipole array antenna. To enhance the gain characteristics, the AMC ground plane configuration is realized with 9 × 9 unit cells for the LPMDA antenna. Two prototypes of the proposed LPMDA antennas with and without an AMC are fabricated and measured to verify its performance. The measured −10 dB reflection ratio bandwidths are 2.56 : 1 (0.85–2.18 GHz) and 2.34 : 1 (0.92–2.16 GHz) for the proposed LPMDA antennas with and without the AMC, respectively. The gain at the main beam direction within the operating frequency bandwidth is significantly improved from 3.94–7.17 dBi to 7.86–10.01 dBi by applying the AMC.

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