When airborne forward looking planar antenna is used to detect ground moving target, targets may be masked by strong clutter due to high sidelobes of the antenna pattern. In this paper, transmitting pattern is synthesized via convex optimization in order to suppress clutter from ground. Transmitting pattern has a low sidelobe illuminating short ranges and a high sidelobe focused into sky and remote ranges, which results in a relative small beamwidth in the elevation plane. In the azimuthal plane, transmitting pattern can form some notches in some fixed directions where strong clutter and interference exist. With insufficient training data due to a dispersion of clutter spectrum along range, adaptive receiving pattern with low sidelobes can be obtained by convex optimization when detecting remote targets. Simulation results show that transmitting and receiving patterns can effectively be designed via convex optimization for airborne forward looking radar.

A planar half mode substrate integrated waveguide (HMSIW) broadband bandpass filter is proposed. It is realized by cascading a lowpass filter and a highpass filter. A transmission line with half mode substrate integrated waveguide (HMSIW) on the circuit board has the characteristic of highpass, while a periodic uniform photo band structure (PBG) array has the characteristic of bandstop. Combining these two structures, a novel compact broadband bandpass filter (BPF) is fabricated and measured. Measured results show that the proposed BPF has wide bandwidth from 11.8 GHz to 23.8 GHz, all the measured insert loss are less than 2.1 dB, return loss are less than 9 dB in the passband. The BPF achieves a wide stopband with 34 dB attenuation low to 5GHz and 27 dB attenuation up to 35GHz.

A simplified expression for the eddy current loss in laminated rectangular core is obtained using linear electromagnetic field analysis. The treatment takes cognizance of current interruption phenomena, by considering capacitive effects of insulation regions. Analysis presented in this paper assumes identical field distribution in each lamination and ignores eddy currents in insulation regions.

In this paper,the propagation model considers the two half-spaces as a homogeneous isotropic medium and one-dimensionally anisotropic medium. From the exact formulas for the transient field with delta-function excitation,it is obtained readily the exact formulas for the transient field excited by a horizontal electric dipole with Gaussian excitation when both the dipole point and field point are located on the boundary between a homogeneous isotropic medium and one-dimensionally anisotropic medium. It is seen that the final exact formulas can be expressed in terms of several fundamental functions and finite integrals,which are evaluated easily.

An open resonance cell (ORC) with finite-length cylindrical mirrors is suggested for making absolute measurements of complex permittivity in the case of stretched cylindrical specimens or liquid dielectrics in cylindrical containers. For H-polarization, we report ORC features simulated in rigorous electromagnetic terms using a twodimensional (2-D) model of an open resonator with cylindrical mirrors and a dielectric test rod inserted. On this basis, the ORC laboratory prototype with finite-length mirrors was built. The measurements of dielectric test rods were performed in the 10 mm wave band. In the studies of dielectric materials, E-polarized modes of the cylindricalmirror ORC demonstrate some specific features, which are discussed, too

This paper presents a novel method for microwave breast cancer detection using a parallel-plate waveguide probe. The method is based on detecting the dielectric contrast between a malignant tumor and its surrounding tissues. Our analysis and simulations indicate that scattered signals from a tumor (modelled as a lossy dielectric sphere with higher dielectric constant than the surrounding tissues) received in the form of S parameter S₁₁ have resonating characteristics in the frequency range of 1 to 7 GHz. A frequency scan of the resonant scattered signals provides data of the presence and location of the tumor. Through numerical examples, the effectiveness of the proposed methodology to detect breast tumors of different sizes, embedded at different depths and to distinguish a tumor from clutter items is demonstrated.

The recurrence dispersion equation of coupled single-mode waveguides is modified by eliminating redundant singularities from the dispersion function. A recurrence zero-bracketing (RZB) technique is proposed in which the zeros of the dispersion function at one recurrence step bracket those of the next recurrence step. Numerical examples verify the utility of the RZB technique in computing the roots of the dispersion equation of the TE and TM modes of both uniform and non-uniform arrays.

This paper deals with Approximate Analytical Solutions to nonlinear oscillations of a conservative, non-natural, single-degreeof- freedom system with odd nonlinearity. By extending the Variational approach proposed by He, we established approximate analytical formulas for the period and periodic solution.To illustrate the applicability and accuracy of the method, two examples are presented: (i) the motion of a rigid rod rocking back and forth on the circular surface without slipping, and (ii) Cubic-Quintic Duffing Oscillators. Comparison of the result which is obtained by this method with the obtained result by the Exact solution reveals that the He's Variational approach is very effective and convenient and can be easily extended to other nonlinear systems and can therefore be found widely applicable in engineering and other sciences.

Abstract-In this paper, a novel ultra-wideband switched-beam antenna system based on 4×4 two-layer Butler matrix is presented and implemented to be used in hostile environment, such as underground mines. This matrix is based on the combination of a broadband twolayer slot-coupled directional coupler and a multilayer slot-coupled microstrip transition. With this configuration, the proposed matrix was designed without using any crossovers as used in conventional Butler matrices. Moreover, this new structure is compact and offers an ultra-wide bandwidth of 6 GHz. To examine the performance of the proposed matrix, experimental prototypes of the multilayer microstrip transition and the Butler matrix were fabricated and measured. Furthermore, a three 4-antenna arrays were also designed, fabricated and then connected to the matrix to form a beamforming antenna system at 3, 5.8 and 6 GHz. As a result, four orthogonal beams are produced in the band 3-9 GHz. This matrix is suitable for ultrawideband communication systems in confined areas.

In this contribution, a two step strategy for the inversion of amplitude-only data in microwave imaging applications is analyzed. At the first step of the proposed method, the illuminating source is synthesized according to a line sources model in order to compute the incident field in the investigation domain starting from the values available in the measurement domain. The second step is aimed at reconstructing the profile of the objects under test thanks to the iterative multi-scaling approach integrated with the Particle Swarm Optimizer, an effective evolutionary minimization technique. The reconstruction accuracy of the proposed phaseless retrieval strategy is analyzed using synthetic data concerned with a multiple scatterer configuration and successively further assessed inverting experimental data.

This paper presents comprehensive measurements of radar backscatter from rice crops using a ground-based 6 GHz C-band scatterometer system. The measurements were conducted over an entire season from the early vegetative stage of the plants to the ripening stage with full polarization combinations of HH, VV, HV and VH at the incident angle range from 0^o to 60^o. The objective of this paper is to access the use of the ground-based scatterometer data for the investigation of temporal variation of different incident angle in the rice growth monitoring application. A further study on the angular response for different rice growth stages was also performed in order to have a better understanding of the backscattering behavior of the rice crops and therefore, monitoring of rice crops growth using operational scatterometer system.

In this paper we study the behavior of wave radiation of a horizontal electric dipole antenna with grounded metamaterial substrates formed by using coordinate transformation technology. From theoretical analysis and simulation results, we can find that such metamaterial substrates not only improve the directive emission but also enhance the radiation efficiency as the dipole antenna gets closer and closer to the metallic ground plane. We thus demonstrate that the transformation medium can offer a theoretical basis for designing a compact planar antenna with transformation media as substrates.

New electromagnetic models for the rods and cones that are the photoreceptors at the back of the retina are developed and simulated in order to explain the roles of dimension, geometrical structure, directional sensitivity and visual pigments of the photoreceptors in the reception of visible light. The rods and cones are modeled as uniform and quasi-tapered helical antennas, respectively. The results of the model study show that if the model antennas have the original photoreceptor cell dimensions, the frequency responses of the model antennas and the spectral sensitivities of the photoreceptors would be very close to each other. In addition, it's observed that the spectral sensitivities of L, M and S cones are broadband over the visible light spectrum, and there are secondary peaks beside main peaks in the spectral sensitivity curves of the cones, because of the conical shape of the cones. It's also observed that there is only one main peak in the spectral sensitivity curves of the rods, because of the uniform and cylindrical shape of the rods. Finally, an array of the novel modeled antennas is also discussed to be used in biomedical applications of artificial retinal photoreceptors in medicine, although the main scope is not designing artificial retinal photoreceptor prosthesis.

The Development of numerical techniques enables us to analyze a large number of complex structures such as dielectric resonator (DR) filters and planar passive elements for coplanar monolithic microwave integrated circuits. As for DR filters, numerical analysis of these structure is highly intricate mostly because of their non-homogenous composition (dielectric constant of DR is greater than 80, dielectric constant of the maintainer is less than 2 and dielectric constant of the atmosphere is 1). Hence, numerical analysis of such a structure, either in time domain (TLM, FDTD and . . . ) or frequency domain (FE, moment, mode matching, boundary element, FD and . . . ) is both complex and time-consuming. From one hand, the non-homogenous structure and from the other hand, the high frequency of applications, demand high density meshing in order to achieve accurate response [1-3]. The explained method in this paper enables us to design a Chebyshev band passes filter by coaxially placing high-Q TM_01δ dielectric resonators in a cutoff circular waveguide. In the presented work, discussions are made regarding high-Q resonators and interresonator coupling. It can be used for TE and TM modes of dielectric resonators. The advantages of such a method are simplicity and accuracy. Furthermore, this method is very quick in calculating resonant frequencies of a single dielectric resonator and coupling factor between two dielectric resonators. Compared with HFSS software, the total required time in this method is less than 1 percent. Based on the presented method, a DR filter is designed, implemented and fabricated and the results are provided. The fabricated filter has an exclusive feature, i.e., it contains no screw for frequency tuning and it gives out the desired result without a need to modification.

In this paper, we apply the Shannon wavelet basis functions to the method of moments to evaluate the radar cross section (RCS) of the conducting and resistive surfaces. The problem is modeled by the integral equations of the first or second kind. An effective numerical method for solving these problems based on the moments method and using Shannon wavelet basis functions is proposed. The validity and accuracy of the method is checked on some examples, and the Shannon wavelets are compared with the well-known block-pulse functions (BPFs) from the viewpoint of computational efficiency. The problem of evaluating the RCS is treated in detail, and illustrative computations are given for some cases. This method can be generalized to apply to objects of arbitrary geometry and arbitrary material.

In the present work, a precise optimization method is proposed for tuning the parameters of ITU-R P.1546 recommendation to improve its accuracy in VHF and UHF propagation prediction. In this optimization method, the genetic algorithm is used to tune the model parameters. The predictions of the tuned model are compared with those of the ITU-R P.1546 recommendation and verified in comparison with some electric field strength measurements obtained by utilizing the IS-95 pilot signal in a commercial CDMA network in rural Australia.

In this paper, the region of interest consists of a perfect conductor, coated with the two layer dielectrics under the air. The completed analytical formulas have been derived for the electromagnetic field due to a vertical electric dipole in the four-layered region when both the source point and observation point are located in the upper dielectric layer. Similar to the three-layered case, the trapped surface wave, which is contributed by the sums of residues of the poles, can also be excited efficiently by a vertical electric dipole in the four-layered region. The lateral wave is determined by the integrations along the branch cuts.

Copper-cobalt ferrites with general chemical formula Cu_xCo_1-xFe₂O₄ (with x = 0.0, 0.4, 0.6 & 1.0) were prepared by ceramic method. The solid state reaction was confirmed by XRD patterns. DC conductivity was measured by two probe method. Electrical resistivity is found to increase on lowering of sintering temperature and time. At x = 1.0, the conduction is mainly due to hopping of electrons leading to n-type conductivity while at x = 0.0, conduction is due to holes leading to P-type conductivity. The lowest conduction at x = 0.4 is attributed to the electron hole compensation. SEM micrographs were obtained from JEOL scanning electron microscope. The micrographs reveal that an average grain size increases with sintering temperature and time as a result of decrease in porosity. This leads to the decrease in resistivity with sintering temperature and time. One of the factors for higher conductivity in ferrites is an increase in average grain size and decrease in pore concentration during the heat treatment.

An effective method for improving the characteristics of the microstrip parallel coupled line coupler is proposed. Some grooves are oriented parallel to the strips and just next to them. It can be shown that an appropriate depth of the grooves can be used for equalizing the even- and odd-mode phase velocity in a coupled microstrip lines with proper geometrical dimensions. Sets of design graphs are derived for various depths of grooves as a parameter and with curves that implies phase velocity equalization curves. The simulated scattering parameters for couplers in conventional and proposed topology show the efficacy of the new grooved substrates.

By properly exciting higher order modes at an aperture it is possible to achieve higher aperture efficiencies. High efficiency antennas are mandatory in many applications, as discrete lenses, since the single element efficiency deeply affects the efficiency of the whole lens. In this contribution a genetic algorithm is applied to the mode matching analysis of square horns to achieve high radiation efficiency over a relatively wide band.