active phased array antenna has been developed that is capable of wide scanning angle with small deviation in antenna gain using printed dipole antennas with parasitic element, which may have the capability of adjusting the influence of mutual coupling in the array element pattern. The design of the parasitic element is examined and the effect of its shape on pattern characteristics is confirmed. Beam scanning angles of 58 degrees in the φ= 0。 plane were obtained for each array antenna pattern.
In this paper, the channel estimation in multi-band OFDM (MB-OFDM) ultra-wideband (UWB) based multiple- antenna transmission systems is studied. For multiple antennas, each preamble designed by the Zadoff-Chu sequence satisfies the orthogonal property in the time domain. Therefore, the proposed preambles can improve the system performance and be applied to MB-OFDM specification in the case of more than two transmit antennas.
Triangular patch resonator bandpass filters with tunable operation are developed to perform nicer filter properties of low passband insertion loss, transmission zeros and wide stopband. With tunable fractal-shaped defection acts as perturbation, filter operation frequency and operation band can be controlled, and the responses of undesired resonant modes are greatly weakened even suppressed. The new design can bring filters more operation without changing the dielectric substrate or patch size. The designed filters have outstanding advantages of single patch with compact size and without resonator coupling gaps, simple circuit topology, nicer performances, miniaturization and can be easily tuned for more applications. All these features are well popular for wireless communication systems.
In this paper, we have simulated a single-pin-shorted microstrip line fed three-dielectric-layer (with different permittivity and thickness) rectangular patch microstrip antenna for all those communication systems whose limited antenna size is premium. Low permittivity hard foam has been used as one substrate to achieve wide bandwidth. The simulation of this proposed antenna has been performed by using CST Microwave Studio, which is a commercially available electromagnetic simulator based on the finite difference time domain technique.
The transmittance is studied for a Cantor-like multibarrier system. The calculation are made in the framework of effective mass theory. Some typical values of effective masses and potentials are used in order to have an experimental reference. The techniques of Transfer Matrix are used to calculate the transmittance of the entire structure having some dozens of layers. The results display a complex structure of peaks and valleys. The set of maxima is studied with the tool of the q-dependent dimension D(q). The set of transmittance maxima exhibits a fractal structure, or more exactly, a multifractal structure, i.e., a q-dependent dimension, characterized as usually with limit one when q parameter tends to -∞ but witha limit between 0 and 1 when tends to +∞. This numerical experiment demonstrate that spatially bounded potential may exhibit spectrum with fractal character.
Taking the advantage of common waveguide filters and SIW technology, a new filter structure is proposed.This structure can be implemented for various microwave frequencies by choosing appropriate low loss substrates.An example of suggested structure in Ku band is presented in this paper.The filter is designed and simulated on a low loss RT/Duroid 5880 laminate.The resulted filter has a Quality factor around 150.The main advantage of the structure is low size and cost, simplicity in fabrication, and the ability of integration with other elements of the circuit.
In this paper a method of moment based analysis of an H-plane 1:3p ower divider has been presented using Multi Cavity Modeling Technique (MCMT) in transmitting mode. Finally attempt has been made to improve the frequency response characteristic of the above mentioned waveguide circuit using a sorting post to diversify the power equally in all the ports. Codes have been written for analyzing the frequency response characteristic of the structure, mentioned above. Numerical data have been compared with the data obtained with laboratory measurement, and CST Microwave Studio simulation. In the present analysis global basis function has been used. The existence of cross polarization components of the field inside the waveguide structures if exists, have also been considered to obtain an accurate result. The proposed power divider has good agreement with the theoretical; CST microwave studio simulated data and measured data. The power divider can be used in the input at 9.8 GHz frequency band, over 800 MHz.
Conventional interferometric inverse synthetic aperture radar three dimensional imaging only consider broadside imaging condition. In this paper, squint model imaging configuration is discussed and the coordinate transform equation is given. The ISAR range profile envelope alignment problem among different antennas are also discussed. Simulation results show the effectiveness of our proposed method.
Data recording on biological tissues and prostheses with femtosecond laser processing for personal identification is demonstrated. The target materials are human fingernails (fingernail memory) and dental prostheses (dental memory). Because they have unexpected movements and individual three-dimensional shapes, the processing system is required an adaptive focusing and highthroughput recording capability. The adaptive focusing is performed with a target surface detection. The high throughput is realized by parallel laser processing based on a computer-generated hologram displayed on a spatial light modulator. Two-dimensional and threedimensional parallel laser processing of glass is demonstrated.
An approach for the microwave nonlinear device modeling technique based on a combination of the conventional equivalent circuit model and support vector machine (SVM) regression is presented in this paper. The intrinsic nonlinear circuit elements are represented by Taylor series expansions, coefficients of which are predicted by its support vector regression (SVR) model. Example of a SiC MESFET nonlinear model is demonstrated, and good results is achieved.
By discussing the basic schemes of the terahertz generation methods based on the 1550-nm ultrafast lasers briefly, GaAs and ZnGeP2 are likely to be promising nonlinear optical crystals for terahertz waves generation by using optical rectification process. However, the mismatches of velocities between the terahertz waves and optical pulses are so large that the phase-matching coherent lengths are quite short, for example, the coherent length of 0.7mm for GaAs and 0.5mm for ZnGeP2 at 2 THz around, respectively. That limited extremely the applications of these bulk excellent nonlinear optical crystals in terahertz regime. In this paper, we demonstrated theoretically that the dielectric planar waveguide could be used to enhance the coherent length of optical rectification process in THz regime. And for the first time, a dielectric planar THz waveguide that has potential applicable value in THz generation by optical rectification method was proposed. We predicted that the effective coherent length could be extended to 4mm at 2 THz in a GaAs/ZnGeP2 dielectric planar waveguide during optical rectification process pumped by ultrafast optical pulses at wavelength of 1550 nm.
A concept of moving dielectrophoresis electrodes (MDEP) based on Microelectromechanical Systems (MEMS) actuators is introduced in this letter. An example design of tuneable dielectrophoresis filter is presented. Finite Element Analysis of the electrostatic field of the tuneable filter has been conducted. Results show that the trapping force can be adjusted by actuating the MEMS actuators.
The first calculation of mobility and conductivity between source and drain as function of gate voltage in a δ-doped Field Effect Transistor is presented. The calculation was performed with a model for the δ-FET that was shown in . The mobility was calculated using a phenomenological expression that was presented in . That expression does not have empirical form, neither empirical parameter. For the first time a phenomenological expression of the conductivity is presented, which is derived from the mobility expression. The conductivity shows three different regions: a parabolic region and two linear regions. The parabolic region represents the region at which the conduction channel begins to close. On the other hand, the mobility shows a more different behavior. In the mobility there are four regions. These regions correspond to the disappearance of the different conduction channels that form the subbands of the deltadoped quantum well. The different behavior between mobility and conductivity relies on the depletion of the delta-doped quantum well as the gate potential grows.
In this paper, complementary spilt ring resonator (CSRR) is applied to design harmonic suppression microstrip rat-race and branch-line coupler. As the CSRR cell is etched on the ground plane of the substrate, the frequency selective properties have a considerable relation with its geometry parameters, which has been analyzed detailedly. As demonstration, a rat-race and a branch-line coupler are designed and fabricated using conventional printed-circuit board fabrication process. The proposed couplers show the performance as good as that of the corresponding conventional structures, but deep harmonic suppression in addition. The design and simulation have been performed using full-wave EM TOOLS ADS Momentum.
Combined ground penetrating radar and metal detector equipment are now available (e.g., MINEHOUND, ERA Technology- Vallon GmbH) for landmine detection. The performance of the radar detector is influenced by the electromagnetic characteristics of the soil. In this paper we present an experimental procedure that uses the same equipment for the detection and calibration by means of signal processing procedures for the estimation of the relative permittivity of the soil. The experimental uncertainties of this method are also reported.
In this paper, the numerical simulations of photoinductive imaging (PI) method have been performed using the finite element method (FEM) with the 2D transient to characterize corner cracks at the edge of a bolt hole. The PI imaging results have higher spatial resolution in the area of the defect in 2D models as compared with the conventional eddy current (EC) images. The FEM simulation results of 0.5-mm rectangular defects are showed and analyzed. The dependencies of PI signals on EC frequencies and temperature of the thermal spot are also examined. The results demonstrate that the PI method is applicable to examine the geometric shape of corner cracks.
In this work tight binding calculations in Be δ-doped GaAs quantum wells with an electric field applied along the  growth direction are presented. The Stark shifts of the hole electronic states for different impurity concentrations and electric field strengths are calculated. The δ-potential is treated as an external potential following the approach described earlier. A comparison with Stark effects in rectangular and graded-gap quantum wells is made.
In this work, CPW-to-stripline (SL) vertical via transitions using gradually stepped vias and embedded air cavities are presented for V-band LTCC System-on-Package (SoP) applications. In order to reduce radiation loss due to abrupt via discontinuities, gradual via transitions are proposed and investigated. In addition, in order to reduce increased parasitic shunt capacitance due to stepped via structures, air cavities are embedded below the transition vias. Using a 3-D EM simulation tool, the proposed transitions are designed and analyzed, compared to the conventional transition. Three-segment transmission lines (CPW-SL-CPW) in 7-layer LTCC dielectrics were fabricated and measured. The two stepped via (STV2) transition embedding air cavities shows an insertion and return losses of 1.6 dB and below -10 dB, respectively, over 60 GHz. The transition loss per one STV2 transition is 0.7 dB at 60 GHz.
A hybrid method of boundary element method (BEM) combined with conformal transformation (CT) is presented to calculate the capacitance of the unscreened slab lines. Conformal transformation transforms the infinite boundary boundary-value problem with the unscreened slab line into a finite boundary one that can be solved by the BEM, then the capacitance of the unscreened slab line is obtained by the BEM. Three representative computational examples, unscreened cylindrical single-bar slab line, unscreened rectangular single-bar slab line and unscreened cylindrical-bar coupled slab line, are given to validate the accuracy and efficiency of the CT-BEM hybrid method.
Polarimetric SAR Interferometry can be used for parameter inversion of ground. An appropriate model is of most importance for parameters inversion. This paper derives a series of scattering model that can be used for parameter inversion of forestry area, such as RV, RVoG, OV and OVoG. These models can reveal the characteristics of forestry area as well as establish the relationship between observed data and parameters of test area. Finally, a multi-layer random scattering model that can be used for parameter inversion of forestry area containing a man-made target is derived. An improved model is examined by the simulated data of the singlebaseline polarimetric SAR interferometry. The result turns out that the improved RVoG scattering model is correct.
Radiation of a Hertzian dipole in a short-ended conducting circular cylinder with narrow circumferential slots is presented. Modematching and Fourier transform were utilized to derive a system of simultaneous equations for modal coefficients. Computations were performed to confirm the fast convergence of the series solution.
An ultra-wideband (UWB) U type monopole antenna fed by a coplanar waveguide (CPW) is proposed. It has low profile and very compact size (14.48mm×28.74mm×0.8 mm). It provides an wide impedance bandwidth ranging from 3.08 GHz to about 12.75 GHz adjustable by variation of its parameters, such as the relative permittivity and thickness of the substrate, width, and feed and ground plane dimensions. Parametric study is presented. Details of the proposed ultra-wideband design are described. Simulation results are presented and discussed in this paper.