Interference Bands Research Articles

A Deception Jamming Method Countering Bi- and Multistatic ISAR Based on Micro-Doppler Effect

Bi- and multistatic inverse synthetic aperture radar (ISAR) operate with spatially separated transmitting and receiving antennas. A deception jamming method countering bi- and multistatic ISAR is proposed in this paper based on the study of micro-Doppler effect. The jammer modulates the intercepted ISAR signals with added micro-Doppler information and retransmits them to the real target, which scatters the jamming signals to the radar receivers. Deceptive false-target images with interference bands in the cross-range direction will be induced by the jamming signals through the imaging process of radar receivers. Additionally, real-time movement features of the false-targets can be flexibly adjusted by changing the modulation parameters, which improves the fidelity of the false-targets. The equivalent number of looks (ENL) index is used to evaluate the jamming effects. Simulation results validate our theoretical analysis and show the effectiveness and practicability of our method.

Compact Unit-Cell-Based Semi-Fractal Antenna with Filtering Properties of Interference Bands Embedded with CBP Strips

ABSTRACTIn this paper, a compact coplanar waveguide (CPW)-fed Ultra Wide Band (UWB) semi-fractal (SF) antenna with dual band filtering characteristics and enhanced bandwidth is presented. The main features of the proposed SF-antenna are the small size of 15 × 15 mm2 dimensions and band-notched characteristics that are obtained without changing the SF radiator. Dual band-notched characteristics are achieved by having a pair of a specific form of shaped strips embedded as conductor back plane (CBP) and defecting CPW ground surface. Also, wider impedance bandwidth can be achieved with this unit-cell-based fractal structure on the radiator. The measured results illustrate that the proposed SF-antenna operates over the VSWR < 2, except two notched bands (3.25–4.32 and 5.02–5.97 GHz), aimed at suppressing any interference from WiMAX IEEE802.16 (3.3–3.6 GHz), C-band (3.7–4.2 GHz), and wireless local area network IEEE802.11a (5.15–5.825 GHz). The SF-antenna has a desirable radiation pattern and gain characteristics for UWB frequency band range. Measured results of the fabricated SF-antenna with the specific form of CBP, unit-cell patterns for radiator and defected CPW ground are presented.

Adaptive Out-of-Band Interference Suppression for Coexistent Wi-Fi and Bluetooth Systems

Coexistence of Wi-Fi and Bluetooth (BT) systems is often necessary in various handheld devices. Due to nonlinearities of radio frequency front-end components, leakage signals from one transmitter to the other transmitter would produce out-of-band (OOB) interference and corrupt adjacent frequency bands outside the spectral masks defined in standards. In this letter, we propose an adaptive OOB interference suppression scheme based on a modified normalized least mean-squared algorithm for coexistent Wi-Fi and BT transceivers. Computer simulation results show that the proposed approach provides pretty good performance in transmitter leakage cancellation and effectively relieves the OOB interference issue.

CPW Fed UWB Antenna by EBGs With Wide Rectangular Notched-Band

Ultra-wideband (UWB) antennas with wide rectangular notched-band are proposed in this paper. The rectangular notched-band design is realized by placing dual mushroom-type electromagnetic-bandgap (EBG) structures on the CPW feeding line. The patches of the EBGs are laid on the back size of the substrate and dead against the CPW feeding line. Shorting pins are utilized to connect the patch and the feeding line. Then, the CPW feeding line operates as ground plane for the EBGs. By tuning the two resonant frequencies of the EBG structures and making them merge with each other, a rectangular notchedband is achieved. Research also found that design methodology has the ability to tune the width and the frequency of the rectangular notched-band by adjusting the EBG parameters. Then, three cases of rectangular notchedband designs to reject the wireless local-area network (WLAN, 5.150-5.825 GHz) interference band and the X -band downlink satellite communication band (660 MHz, 7.10-7.76 GHz) were designed by using different EBG parameters. The design methodology can also be utilized to design rectangular notchedband for other interference bands efficiently.

Optical properties of As2S3 layers deposited from solutions

This paper presents results of the preparation and optical characterization of As2S3 layers by using spin or dip-coating technique and As2S3 solutions in ethylenediamine and n-propylamine as solvents. These solutions were prepared from arsenic sulfide powders obtained from laboratory-prepared bulk glasses. Ethylenediamine and n-propylamine solutions with the same As2S3 concentration of 0.7mol/l were used for the layer preparation.Layers were prepared by both the dip-coating and spin-coating techniques with velocity of 0.2–30cm/min and 2000rpm for 90s, respectively. Substrates used in these experiments were microscopic slides (refractive index of about 1.49). All applied As2S3 layers were dried in vacuum for 60min and then heat-treated at 180°C for 60s in nitrogen atmosphere.Prepared As2S3 layers were characterized by transmission spectroscopy in the wavelength range of 200–100nm. Thicknesses of applied layers in the range of 200–1500nm and their refractive indices ranging from 1.7 to 2.3 at 800nm were estimated from interference bands in measured transmission spectra using Swanepoel's method. Dispersion curves of the refractive index are shown in the paper. Optical band gaps of prepared layers in the range of 2.15–2.35eV were determined from measured transmission spectra by using Tauc's extrapolation.

Method of reducing speckle-interferometer sensitivity for the study of turbomachine elements vibration

The article deals with the development of a method for obtaining time-averaged speckle-interferograms with a two-fold period of interference bands. An optical scheme allowing the increase of permissible vibration amplitudes of the analysed elements has been developed. Vibration characterictics of compressor stage 5 blades are subjected to comparative analysis with the use of both the developed method and the traditional methods. The diagram of compressor blade leading edge vibrodisplacements is made up on the basis of the data obtained.

DESIGN AND TIME-DOMAIN ANALYSIS OF COMPACT MULTI-BAND-NOTCHED UWB ANTENNAS WITH EBG STRUCTURES

Four ultra-wideband (UWB) antennas are proposed: one referenced antenna without notch and three novel antennas with one, two and three notched bands, respectively. The UWB referenced antenna consists of a beveled rectangular metal patch, a 50› microstrip line and a defective ground plane. Then, by utilizing one, two and three electromagnetic band-gap (EBG) structures on the UWB antenna, the antennas present one, two and three notched- band responses, respectively. The frequency domain characteristics including VSWR, transfer coe-cient S21, radiation patterns and group delay are investigated. It is found that the EBG design approach is a good candidate for frequency rejection at the certain frequencies, owing to high performance of notch design and the notched-band bandwidth control abilities. Meanwhile, these abilities also enable less useful frequencies rejected. The design examples exhibit good band- rejected characteristics in the WiMAX/WLAN interference bands (3.4, 5.2 and 5.8-GHz bands). Moreover, good time-domain characteristics of the antennas are checked based on group delay, waveform response, correlation coe-cient and pulse width stretch ratio (SR).

Structure and physical properties of colloidal crystals made of silica particles

The relationship between the particles size distribution of colloidal crystals and the structure and physical properties of the resulting 2D colloidal crystals is presented in this work. The colloids were constituted of silica sub-micron spheres with different size distributions comprised between 150 and 520nm, synthesized by the Stöber method and assembled in one monolayer through the Langmuir–Blodgett technique. Optical and wetting properties of the resulting crystals were studied by different techniques – UV–visible spectrometry, spectroscopic ellipsometry and contact angle measurements. They were related to the crystal structure which was analyzed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The conservation of orientational and translational orders over a large area is found for crystals with narrow particle size distribution. Optical interference bands in the transmittance spectra are linked to the crystal periodicity and the presence of optical anisotropy is attributed to distortions in the film generated by the deposition process. Moreover, large particle size distribution results in the most hydrophobic crystals. Thus the physical properties of the colloidal crystals can be tailored or tuned by controlling the particle size distribution and the deposition parameters.

Symmetric Talbot bands experiment

By impinging a step phase-shifted white light beam on a grating-based interferometer, one of diffraction orders is modulated and interference bands so-called “Talbot bands” are formed. Here, classical Talbot bands set up is generalized to the symmetry configuration, in which two glass plates of the same thickness instead of one plate, are inserted halfway into the grating interferometer aperture. Formation of Talbot bands were studied theoretically and experimentally. Frequency impulse response of the new Talbot bands setup was, also presented. It was demonstrated that symmetric set-up causes modulation of both of two opposite orders, according to the theory. In this manner, their visibility is the same. As a result, this similarity of the visibility is reduced while the symmetric arrangement of the glass plates with respect to the optical axis, is broken.

UWB Band-Notched Monopole Antenna Design Using Electromagnetic-Bandgap Structures

A new approach is proposed to reject certain bands within the passband of an ultra-wideband planar monopole antenna. The proposed approach that utilizes a mushroom-type electromagnetic-bandgap (EBG) structure is proven to be an effective way for band-notched designs. The approach has many advantages, such as notch-frequency tunability, notch-band width controllable capacity, efficient dual-notch design, and stable radiation patterns. Several design examples using conventional mushroom-type EBG and edge-located vias mushroom-type EBG are presented. The examples exhibit good bandstop characteristics to reject the wireless local-area network interference bands (5.2- and 5.8-GHz bands). Besides, the causes that lead to the discrepancies between the simulations and measurements are discussed.

The outlook for X-ray diffraction topography

The possibilities of high-resolution X-ray section topography using the geometry of the interference bands to reveal features of the elastic fields of crystalline lattice defects are considered. The mechanisms of the diffraction of the X-ray wavefield on elastic lattice distortions are demonstrated using the example of dislocations. Microdefects in silicon are another most interesting subject. Section topography is in this case virtually the only method for revealing very weak deformations due to microdefects.

An Autonomous Interference Detection and Filtering Approach Applied to Wind Profilers

An autonomous interference detection and filtering algorithm has been developed for removing the interference bands generated in the Doppler spectra of mesosphere-stratosphere-troposphere (MST) radar signals. The technique, implemented with the MST radar at Gadanki (13.5° N, 79° E), is based on identifying interferencelike band signals using a statistical signal variance approach for fixing the amplitude threshold, through which detecting the interference frequency and designing an adaptable notch filter to filter the undesired frequency bands are done. Signals received from the MST radar are sometimes contaminated with interference signals received from other objects or generated within the system through arcing of high-power devices. Multiple interference bands with different characteristics are observed in the power spectra, which contaminate the wind information and other atmospheric signals. The autonomous interference detection and filtering algorithm is applied to various cases, and it is found that the interference signals could effectively be removed, leaving behind the original signals. By this approach, the effective number of signal samples obtained is increased, which helps one to improve the temporal resolution.

Lepton-number-violating decays of singly-charged Higgs bosons in the type-(I + II) seesaw model

The lepton-number-violating decays of singly-charged Higgs bosons H± are investigated in the minimal type-(I + II) seesaw model with one SU(2)L Higgs triplet Δ and one heavy Majorana neutrino N1 at the TeV scale. We find that the branching ratios B(H+ → lα+ν̄) (for α = e,μ,τ) depend not only on the mass and mixing parameters of three light neutrinos νi (for i = 1,2,3) but also on those of N1. Assuming that the mass of N1 lies in the range of 200 GeV to 1 TeV, we figure out the generous interference bands for the contributions of νi and N1 to B(H+ → lα+ν̄). We illustrate some salient features of such interference effects by considering three typical mass patterns of νi, and show that the relevant Majorana CP-violating phases can affect the magnitudes of B(H+ → lα+ν̄) in this parameter region.

Laser interference method of determining the parameters of gas bubbles

The fundamentals of the laser interference method of determining the parameters of gas bubbles in liquids and solids are considered. The role of polarization in the development of interference bands is analyzed. Features in the realization of an experimental plant and a technique for performing experiments are presented.

Vibrational spectroscopy characterization of magnetron sputtered silicon oxide and silicon oxynitride films

Vibrational (infrared and Raman) spectroscopy has been used to characterize SiO x N y and SiO x films prepared by magnetron sputtering on steel and silicon substrates. Interference bands in the infrared reflectivity measurements provided the film thickness and the dielectric function of the films. Vibrational modes bands were obtained both from infrared and Raman spectra providing useful information on the bonding structure and the microstructure (formation of nano-voids in some coatings) for these amorphous (or nanocrystalline) coatings. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) analysis have also been carried out to determine the composition and texture of the films, and to correlate these data with the vibrational spectroscopy studies. The angular dependence of the reflectivity spectra provides the dispersion of vibrational and interference polaritons modes, what allows to separate these two types of bands especially in the frequency regions where overlaps/resonances occurred. Finally the attenuated total reflection Fourier transform infrared measurements have been also carried out demonstrating the feasibility and high sensitivity of the technique. Comparison of the spectra of the SiO x N y films prepared in various conditions demonstrates how films can be prepared from pure silicon oxide to silicon oxynitride with reduced oxygen content.

Infrared reflectivity spectra of thin porous aluminum oxide films

AbstractAngular dependencies of infrared (50–7500 cm–1) reflectivity spectra of thin porous aluminum oxide films on aluminum had been measured. These spectra show vibrational bands and strong interference bands allowing film thickness and dielectric function calculation. Angular dependencies of interference bands give thicknesses and refractive indices of the films. The refractive indices decrease and hence the film porosities increase with the thickness. The dispersion analysis of the reflectivity spectra below 2000 cm–1 allows us to obtain the film dielectric functions in the fundamental vibrations region. (© 2009 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

An Alternate Method for Fourier Transform Infrared (FTIR) Spectroscopic Determination of Soil Nitrate Using Derivative Analysis and Sample Treatments

This study aimed at examining effective sample treatments and spectral processing for an alternate method of soil nitrate determination using the attenuated total reflectance (ATR) of Fourier transform infrared (FTIR) spectroscopy. Prior to FTIR measurements, soil samples were prepared as paste to enhance adhesion between the ATR crystal and sample. The similar nitrate peak heights of soil pastes and their supernatants indicated that the nitrate in the liquid portion of the soil paste mainly responded to the FTIR signal. Using a 0.01-M CaSO4 solution for the soil paste, which has no interference bands in the characteristic spectra of the analyte, increased the concentration of the nitrates to be measured. Second-order derivatives were used in the prediction model to minimize the interference effects and enhance the performance. The second-order derivative spectra contained a unique nitrate peak in a range of 1,400–1,200 cm−1 without interference of carbonate. A partial least square regression model using second-order derivative spectra performed well (R2 = 0.995, root mean square error (RMSE) = 23.5, ratio of prediction to deviation (RPD) = 13.8) on laboratory samples. Prediction results were also good for a test set of agricultural field soils with a CaCO3 concentration of 6% to 8% (R2 = 0.97, RMSE = 18.6, RPD = 3.5). Application of the prediction model based on soil paste samples to nitrate stock solution resulted in an increased RMSE (62.3); however, validation measures were still satisfactory (R2 = 0.99, RPD = 3.0).

Interference bands in decays of doubly-charged Higgs bosons to dileptons in the minimal type-II seesaw model at the TeV scale

The dileptonic decays of doubly-charged Higgs bosons H±± are investigated in the minimal type-II seesaw model with one Higgs triplet Δ and one heavy Majorana neutrino N1 at the TeV scale. We show that the branching ratios B(H±±→lα±lβ±) depend not only on the mass and mixing parameters of three light neutrinos νi (for i=1,2,3), but also on those of N1. Assuming the mass of N1 to lie in the range 200 GeV–1 TeV, we figure out the generous interference bands for the contributions of νi and N1 to B(H±±→lα±lβ±): |sinθi4sinθj4|∼10−8–10−5, where θi4 and θj4 measure the strength of charged-current interactions of N1. We illustrate some salient features of the interference bands by considering three typical mass patterns of νi, and stress that it is very difficult to distinguish the type-II seesaw model from the triplet seesaw model in such a parameter region at the Large Hadron Collider.

Vibrational polaritons in thin oxide and nitride films

AbstractAngular dependencies of infrared reflectivity spectra of thin silicon oxinitride amorphous films on silicon and porous aluminum oxide films on aluminum had been measured. These spectra show vibrational bands and strong interference bands allowing film thickness and dielectric function calculation and providing useful information on the bonding structure of the coatings. Angular dependencies of these bands give the dispersion of vibrational and interference polariton modes in the films. The intersection of vibrational and interference polaritons has been observed for silicon oxinitride film. (© 2008 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Optical Changes and Writing on Hydrotalcite Supported Gold Nanoparticles

Gold nanoparticles (AuNP) incorporated into hydrotalcite (HT), provide an interesting type of pigment in which temperature can modulate the plasmon resonance and the aggregation phenomenon. As inferred from microscopy techniques, the preferential binding sites are located at the border of the HT external basal surface, leading to aggregates of gold nanoparticles displaying characteristic plasmon resonance and interference bands around 520 and 700 nm, respectively. The thermally induced color changes in the HT-supported gold material arise from the competition between of nanoparticles aggregation and fusion processes, as characterized by TEM and STM. A laser beam can also induce such changes, allowing the writing of optical information on this type of material.