Multi Resonance Research Articles

Combination of artificial materials with conventional pyramidal absorbers for microwave absorption improvement

This article addresses the combination of an artificial and conventional absorber materials in order to enhance its absorption properties and compactness. We demonstrate an increase of the absorption performance of the pyramidal absorbers by integrating a metamaterial layer. The latter is composed of two unit cells with multi resonance behavior between 2GHz and 18GHz. The simulation results of the hybrid material predict absorption for normal and oblique incidence of the electromagnetic wave at low and high frequencies depending on the wave polarization.Hybrid materials (metamaterial+conventional pyramidal absorbers) have been achieved using two pyramidal absorbers; the first one is a commercial absorber APM12/SIEPEL and the second one is the same material but with reduced dimensions. These absorbers are made of polyurethane foam loaded with carbon particles. The measurements show an increase of the absorption performance compared to the pyramidal absorber alone, even for the absorber with reduced dimensions.

Analysis and design of a triple band metamaterial simplified CRLH cells loaded monopole antenna

The design and analysis of meta-material inspired loaded monopole antenna for multiband operation are reported. The proposed antenna consists of multi resonators inspired from half mode composite right/left handed cells, which has a simple structure, compact size, and provides multiband functionalities. As a proof of concept, a triple band antenna covering all possible WiMAX operating bands, has been designed, fabricated, and characterized. The hosting monopole patch itself generates resonance for 3.3–3.8 GHz band, whereas the loaded metamaterial cells add extra resonance frequencies. The loading of two resonator cells introduces two extra resonances for 2.5–2.7 GHz and 5.3–5.9 GHz bands, respectively. The antenna's operating principle and design procedures with the aid of electromagnetic full wave simulation and experimental measurements are presented. The antenna has good omnidirectional patterns at all three bands. The monopole patch size is 13.5 × 6.5 mm2and the whole antenna size (including the feed line) is 35 × 32 mm2. Compared with conventional single band microstrip patch radiator, the radiator size of this antenna is only 8.5% at 2.5 GHz, 17% at 3.5 GHz, and 37% at 5.5 GHz.

Microring Resonators and Silicon Photonics

Silicon Photonics is the technological to face the future challenges in data communications and processing. This technology follows the same paradigm as the technological revolution of the integrated circuit industry, that is, the miniaturization and the standardization. One of the most important building blocks in Silicon Photonics is the microresonator, a circular optical cavity, which enables many different passive and active optical functions. Here, we will describe the new physics of the intermodal coupling, which occurs when multi radial mode resonators are coupled to waveguides, and of the optical chaos, which develops in coupled sequence of resonators. In addition, an application of resonators in the label-free biosensing will be discussed.

Sub wavelength plasmonic nano-antenna with H and U shape for enhancement of multi resonance

In this article, Optical electric field enhancement in the normal direction is noticed. For this aim, we selected single H and U-shape array antenna, which are known as a conventional type of the nano-antenna. Both of these antennas are studied in their most common form and then combinations of these antennas are studied for achieving multi- band and improving absorption of the antenna. Here, for all structures, the E-field (electrical field) enhancement in the X direction is studied and design parameter effects on field enhancement are debated. The effect of antenna parameters on resonance frequency and Ex enhancement is studied in this article. In addition, we noticed the effect of the U elements arrangement on E-field enhancement in X direction. Therefore, in current research, the extinction cross section is studied for every structure and formation. For modeling the prototype structures, here SiN is selected for Substrate with n=1.98 and silver with Johnson optical characteristic for metal layer. Simulation has been done in the time domain with CST microwave studio commercial software.

Sub wavelength plasmonic nano-antenna with modified ring structure for multi resonance application and circular polarization

In this article, two different novel models of sub-wavelength plasmonic nano-antenna with modified ring structures for multi resonance applications with circular polarization are presented. At first a quad-ring metamaterial structure is presented, in the following we modified the structure with gaps in each rings. Therefore, the second structure has more absorption and reflection cross section than the first model. The absorption cross section has increased from 1.2E+5 for the first structure at 300 THz to 4.2E+5 for the second structure at 175 THz. In addition, the reflection cross section has increased from 3.7E+5 for the first structure at 300 THz to 5.2E+5 for the second structure at 175 THz. On the other hand, the Enhancement of E2 is an important parameter and shows antenna quality, which improved strongly since 120 (V/m)2 to more than 13,000 (V/m)2 at X-directions. Here, E-field distribution shows that the field is concentrated at gaps in both structures.

Plasmonic cross-junction ring antenna implementation for field enhancement

Nano loop antenna based on plasmonic radiation for optical range is developed to cross junction model to achieve high performance. In this article, to achieve high field enhancement and multi resonances, a cross-junction structure is combined with ring structure and new structure shows two resonances at 750nm and 1300nm for cross-junction ring. In new model, E2 is increased extremely to more than 2400(V/m)2 at 1200nm; but it is around 110(V/m)2 at 1000nm. ACS (absorption cross section) shows grate enhancement at 1300nm where we have the maximum rate of E2.

CPW fed hexagonal micro strip fractal antenna for UWB wireless communications

This paper presents the hexagonal microstrip fractal antenna (HMSFA) for ultra wideband wireless communication applications. Hexagonal antenna is powered through co-planar waveguide (CPW) feed structure. The stepping fed configuration is used to improve the antenna electrical characteristics at the centre and higher frequencies in the FCC designed UWB frequency range from 3.1 to 10.6GHz. The proposed antenna uses a fractal technique to analyze its UWB characterization. The hexagon antenna is designed, simulated and fabricated on a polyamide substrate of dielectric constant ɛr=4.3, thickness t=1.53mm, loss tangent tanδ=0.004 and lande G factor 2. The operating bandwidth of the proposed fractal antenna is about 9GHz more than UWB range. The size of the radiating patch is about 26mm×30mm and the sided length s=15mm, achieves good impedance matching, constant gain, steady radiation patterns, multi resonant and constant group delay over an UWB frequency range from 3.1 to 10.6GHz. This antenna creates the fractal geometry inside the patch with similar in shape but different in sizes. The proposed antenna is fabricated and experimental results are verified in an anechoic chamber of millimetre and antenna lab.

Optical antenna of comb-shaped split ring architecture for increased field localization in NIR and MIR

We propose and demonstrate novel designs of optical antennas based on comb-shaped split ring architecture that display multi resonance field intensity enhancement spectrum. These nanoantennas achieve substantially increased field localization at longer wavelengths than that of a single or an array of dipoles with the same side length. With these optical antennas, localizing near infrared (NIR) and mid infrared (MIR) lights within a region of tens of nanometers at an intensity enhancement level of the order of thousands of magnitude can be accomplished.

Patch Loaded DRA for Broadband WLAN Applications

patch loaded dielectric resonator antenna (DRA) is discussed here. The rectangular ring shaped slot coupling is used to excite the proposed antenna. In this paper, rectangular ring shaped slot coupled DRA and patch loaded DRA is studied and compared. The combined effect of patch radiator with rectangular ring shaped slot coupled DRA, on the return loss is observed. Simulation is done using Ansoft HFSS which is based on finite element method. Simple DRA resonates at two frequencies centered at 2.25 GHz having return loss of - 14.41 db and 4.61GHz with a return loss of -19.29db; The patch loaded DRA shows resonance at frequencies centered around 2.19GHz having return loss of -32.3db and 4.4GHz with a return loss of -29.18db.The patch loaded DRA is based on the multi resonance technique that combines the resonance of slot coupled dielectric resonator and micro strip patch antenna. The bandwidth achieved for simple DRA is 26.8 % while patch loaded DRA offers 44.1 %.As the patch loaded DRA has larger bandwidth, may be used for wideband WLAN applications like WiFi, Bluetooth, Wimax etc.

Characteristics of core refractive index axial asymmetry LPFGs written by femtosecond laser

Direct writing of long period fibre gratings (LPFGs) in standard single mode fibres (SMF) with infrared femtosecond laser pulses is experimentally investigated. It is found that the transmission spectra of LPFGs can be controlled by infrared femtosecond laser focus condition. The transmission spectra of LPFGs present single resonance peak when the microscopic objective is 25´, which is distinct from the LPFGs manufactured by UV laser irradiation with mask. However, when the microscopic objective is 10´, the LPFGs transmission spectra with four rejection bands can be obtained. When the distribution of femtosecond laser energy is changed by inserting a diaphragm, the LPFGs transmission spectra present multi resonance peaks.

ULTRA-WIDEBAND SHORTED PATCH ANTENNAS FED BY FOLDED-PATCH WITH MULTI RESONANCES

Novel designs of probe-fed broadband shorted patch antennas for ultra-wideband (UWB) applications are presented in this paper. In these designs, unequal resonance arms fed by a folded patch produce multi resonances to broaden the impedance bandwidth. In the flrst design, the antenna consists of an asymmetric E-shaped patch, a folded-patch feed and shorting pins. This antenna is achieved by four adjacent resonances with the measured i10dB impedance bandwidth of 76.18%. The pins are utilized to miniaturize the size of the patch. By introducing a folded ramp-shaped feed in the similar structure with the flrst design, a wider bandwidth with the flve resonances is obtained. This improved design introduces an antenna with an impedance bandwidth of more than 110% and a considerable size reduction compared to the flrst antenna. The antennas present resonance tuning ability within the impedance bandwidth by varying the length of unequal arms. In addition, parametric studies are performed by investigating the efiects of difierent key parameters on obtaining optimal designs of the proposed antennas.

A Study on Test Technology of Ship Shafting Torsional Vibration

Ship shafting is a key component of ship power plant. Torsional vibration test for ship shafting is the essential step to ensure the safety of ship power systems. For the purpose of analyzing and comparing torsional vibration test methods, a study of the test methods, equipment and technology is carried out in this paper. Three different test methods are compared with each other by adopting two different test systems. The main propulsion and marine generator shafting torsional vibration characteristics are analyzed by using two different analysis methods respectively: the single order and resonance point method and the multi order and resonance point method. The results obtained in the process of testing on board ship may provide a good guidance for the further researches in this subject.

비선형 소자 탐지용 광대역 스파이럴 안테나의 설계

This paper presents a design of spiral antenna with broad bandwidth for non-linear junction detector(NLJD). An elliptical patch as radiating element located on center position of radiating surface, as well as the spiral elements on radiating surface was designed for broad bandwidth of spiral antenna. An antenna ground structure generating the multi resonance by spiral slit inserted on ground surface was also proposed. In order to realize high directivity and high gain of the proposed antenna, the cavity wall made of Fr4-epoxy and the metal cap were considered in design. As a result, the calculated gain of antenna with metal cap was improved about 3 dB with comparison of antenna without metal cap and the measured main beam directivity toward -z axis direction agreed well with calculation result. The measured axial ratio satisfied the circular polarization within -z axis at design frequency bands and showed reasonable agreement with prediction.

About the resonance approximation in neutron induced reactions

The puzzle of the complete description of (n, γ) angular correlations is discussed. The multi resonance approach is needed for the successful explanation of the recent experimental data.

Modification and generalization of some methods to improve the accuracy of α-determination in the 1/E1+α epithermal neutron spectrum

Some methods described in the literature for the determination of α in the 1/E1+α epithermal neutron spectrum are critically reviewed with respect to their accuracy. The multi resonance—detector method with Cd-covered irradiations, as used by SCHUMANN and ALBERT, is generalized by subtracting the epithermal 1/v-tail and by introducing the effective resonance energy, as defined by RYVES. The two-detector method of RYVES is modified by using Cd-ratio measurements, thus eliminating the introduction of systematic errors due to the inaccuracy of absolute nuclear data. The adapted methods are applied in channel 15 of the Thetis reactor (Gent).